Strange and Non-Strange Particle Production in Proton—Proton Reactions at an Incident Momentum of 19 GeV/c

Uno Svedin

Stockholm 1974 Strange and Non-Strange Particle Production in Proton—Proton Reactions at an Incident Momentum of 19 GeV/c

Uno Svedin

Stockholm 1974 ISBN

CONTENTS

1. The scope of this thesis 7

2. Introduction 11

3. Earlier studi^B of proton-proton reactions 17

4. Experimental procedures 18

5. Resume's of publications belonging to this thesis 21

0. Discussion on some physical items related to our investigations 31 6.1 Integrated cross sections 31 6.2 Average multiplicities 34 6.3 The charge multiplicity distribution 39 6.4 Scaling properties of momentum spectra 47

7. Summary 53

8. Acknowledgement 56

9. References 58

Tables

List of figures

Figures- 1. THE SCOPE OF THIS THESIS

The present thesis is based on studies done within the framework of the Scandi- navian Bubble Chamber Collaboration during the years 1966-1974 and concerns

different aspects of proton-proton reactions at an incident beam momentum of

19 GeV/c.

The presentation is divided into three different parts

I. Studies of final states involving non-strange particles.

II. Studies of final states involving strange particles.

III. Development of equipment.

The main emphasis is on the presentation of atrange particle production

results (Section II of papers). The results have not been discussed in the form

of a thesis before. The sample from which the results are drawn is one of the

largest presented up to this day for proton-proton reactions.

In the discussion on the production of strange particles we make frequent use

of the non-strange final state results.

As many aspects of high energy physics do not show their significance except in

a study over a wide range of initial energies, We will in the discussion (after a

short introduction, a survey on the experimental procedure and resume's of

the included papers), frequently make use of data from other ejqperiments, at

other energies, of compilations earlier presented by,different.physisists,,

(often using our data in part) and of model discussions by various 'authors.

The main aim is to explain how our data and conclusions have fitted into the

pattern of existing high energy physics results. In order to perform any experimental work, developments of & technical nature must take place. In Paper 111:1 the development of an on line system for measuring bubble chamber pictures is described. A part of the strange particle sample has been measured using this system. Paper 111:1 was earlier included in S-O. Holmgrens thesis [l]. Work to improve the quality of the sample is described in Paper 11:3.

Publications included in this thesis are

1:1 H. Bjzfggild, E. Dahl-Jensen, K.H. Hanseji, H. Johnstad, E. Lohse, R. Mbllerud, M. Suk, L. Veje, V.J. Karimaki, K.V. Laurikainen, E. Riipinen, T. Jacobsen, S.O. Sjirensen, J, Allan, G. Blomqvist, O. Danielsson, G. Ekspong, L. Granstrom, S.O. Holmgren, S. Nilsson, B. Ronne, U. Svedin and N.K. Yamdagni: "Some features of particle multiplicities and momentum spectra in inelastic proton-proton colli- sions at 19 GeV/c."Nucl. Phys. B27, 285 (1971).

II.

II. 1 K. Alpgard, T. Buran, H. B^ggild, A.G. Frodesen, V.M. Haginan, K.H. Hansen, J.E. Hooper, P.O. Hulth, H. Johnstad, M. Korkea-Aho, K. Marquit, R. Moller, U. Svedin, II. Tttfte, P. Villanen and N. Yam- uatiiii: "The inclusive single-partible spectra of ff~, K and A in prolon-proton collisions at 19 GcV/c." Nucl. Phys. B57.. 77-99 (1973).

II.2 K. Alpgdrd, G. Ekspong, A-G. Frodesen, V.M. Hagman, P.O. Hulih, V. Kp.rimi.ilci. A. Krogstad, L1. Svedin, P. Villanen and N.K. Yamdagni: "Strange particle cross sections in 19 GeV/c proton-proton interactions and their interpretation in the KNO framework." USIP-Rsport. 74-24 November 1974. 11:3 K. Alpg&rd, P.O. Hulth. U. Svedin and N.K. Yamdagni: Measurements of strange particle production cross sections in proton-proton reactions at 19 GeV/c incident momentum. USIP-Report 74-25, November 1S74.

11:4 The Scandinavian Bubble Chamber Collaboration and the K Coliabora- 4- tion: Factorization in the inclusive reactions pp -• A +Xand K p - A+ X. USIP-Report 74-26, November 1974.

Hi. 111:1 G. Blomqvist, S.O. Holmgren, P.O. Hulth and U. Svedin: A hardware system for measurements of bubble chamber films on-line. USIP-Report 70-03, June 1970. 11

2. INTRODUCTION

A dominant feature of hadron collisions above a few hundred MeV/c incident momentum (17-threshold) is the creation of new particles. In proton-proton reactions at 19 GeV/c, such creations occur in « 75 % of all reactions.

Fig. 1 shows this inelastic part as well as the total cross sections as a func- tion of the incident laboratory momentum for proton-proton re. 3tions. We observe that a large fraction of the total cross section involves the creation of new particles over a wide range of incident momenta.

The produced particles could be of several types: ft , K , K , p, p,

+-0 I , A, etc. There are certain restrictions on the production of these par-

ticles in the form of conservation laws, as the conservation of charge, energy,

baryon number etc.

The earliest identification of an event of what we now call strange particles

was reported by L, Le Prince-Kinguet in 1944 [2]. It was discovered in a cloud chamber exposed to cosmic rays. The mass of the particle was found to be 2 500 ± 50 MeV/c . Such a particle is called a K-meson today. In 1947 Rochester

and Butler [3] , found two cases of "forked" (or V-like) tracks in a cloud cham-

ber . One of them was interpreted as the decay of a new type of uncharged

elementary particle decaying into two lighter charged ones. The mass was

estimated to be of the order of 1000 electron masses. Today we know there are

two types of V°-particIes called A and K°. After extensive work in many labora-

tories this was definitely established by R.W. Thompson et al. [4].

Whereas the strange particles were produced copiously (a 1 %..of the ff-meson _HQ . production), they had lifetimes > 10 sec. From the production cross section it 12 was derived that the matrix element, e.g. for A production, should be of the order of one-third of that of the Yukawa interaction. Thus assuming the same mechanism which produces the V-particles also to be instrumental in their decay, —22 12 one would estimate lifetimes of the order of 10" seconds, a number of 10 smaller than the experimental one. Due to this puzzle the particles were called "strange".

Pais [5] solved this difficulty by suggesting that the production of strange par- ticles occurs in pairs only. The decay and production processes thus involve different particles and cannot be simply related.

Experiments in 1953 , including the first artificial production of K's at the new cosmotron at Brookhaven [6], established that the production of V s(K or A) occurs in pairs only - "associated production" [7].

This whole subject was systematized in 1953 by Gell Mann [8] and almost simul- taneously by Nakano and Nishijima [9]. They introduced a new additive quantum number, later called strangeness [10], which was postulated to be conserved in strong interactions. Particles given strangeness quantum number not equal to zero were accordingly called "strange particles". Strict conservation of "strange- ness" in strong interactions corresponds to "associated production" of V-particles.

A strangeness breaking decay is not possible via strong interaction. Such a decay is however possible via weak interactions, thus giving the long life times

observed. In the presently accepted classification scheme for elementary particles,

based on group theoretical considerations (SU_) (introduced by Y. Ne'emanand

M. Gell-Mann), the strangeness number is one of the Important classification *- properties for particles. 13

During the last years more and more interest has been shown in questions on the general dynamics of reactions (questions of duality, Regge and Pomeron ex-

changes, scaling, etc.). Studies of the behaviour of strange particle3 have con-

tributed to the understanding of high energy phenomena.

The present thesis deals with the production of strange particles produced in

proton-proton interactions at an incident momentum of 19 GeV/c. It also com-

pares the production of strange particles with the production of non-strange

particles also produced in 19 GeV/c pp-reactions.

The experiment was performed using the CERN Proton Synchrotron (PS) giving

beam momenta up to *» 28 GeV/c. In order to get a fair amount of strange

particlb events we collected at the Bubble Chamber exposures (described be-

low) around ra500 000 pictures.

After the new generation of high energy proton accelerators came into opera-

tion (at Serpukov, USSR, pT ._ up to 70 GeV/c, at NAL, Batavia, USA, p_ up to

fa 400 GeV/c, at CERN ISR up to a corresponding incident momentum of« 1500

GeV/c), a set of experiments studying strange and non-strange production in

proton-proton reactions have been performed. Many of these experiments have

studied a small sample of pictures (a few tens,of thousands) giving large .'•-..

statistical errors. The restricted number of pictures is however somewhat

compensated, what the strange purtiole production concerns, by the increasing .

cross sections. ' • •'.'••' :'••'••'•'•.'". '"\: '• •••'_••, ..;:' •'.. •

' • • • • 1 ' - •'**•.• A reaction

; • A •F13Jfch.+:ch; + .";r.ch' •••+--N-VN- Vi.-. N-' .1 z • n. i .4 m 14

(A is the beam and B is the target particle, Ch .. .Ch are charged secondaries) is often referred to as a "channel" if all particles in the final state are identified and measured. When the incident momentum increases, the number of charged par- ticles increases, which makes it more and more difficult to analyse a separate chan- nel. Also the number of neutrals (N.... N ) must uot exceed 1 for such a study *).

Instead, it is possible to perform measurements) in which only one (c) of the final state particle types are detected in a collision, without caring what else may also be produced. Such "inclusive" reactions [11, 12]

a + b — c + anything * (1) are often schematically depicted

Examples of such reactions, studied by us, are

pp - n + anything (2a)

pp - K° f anything (2b)

PP - A° + anything (2c)

We have also studied "semi-inclusive" reactions

a + b —c+d + anything (3)

as

pp - A + K° + anything (4)

*) Studies of channels are sometimes called "exclusive" studies. 15

Studies of inclusive and semi-inclusive reactions build the dominant, part of this thesis. The results are compared to what has been found at other energies. The

overall production cross sections for various particles will be given. The distribu-

tion of cross sections as a function of charged multiplicity will be discussed for

various subsets of samples, especially in the framework of Koba, Nielsen and

Olesen (KNO) [13].

The exclusive and the inclusive types of investigations are often said to be com-

plementary to each other. A complete measurement of all inclusive cross sec-

tions implies a complete knowledge of ail exclusive cross sections and vice

versa [14]. Practically we cannot isolate all inclusive (or exclusive cross sec-

tions). We will have to do with some of them, as the Lorentz invariant cross

section

3 f(ab-cx) = E 2-2 (5) ^c

for the inclusive reaction (1) where E is the energy of the particle c produced

and x is "anything". Such inclusive invariant cross sections will be presented

and discussed in this thesis. By generalizing the optical theorem, Mueller [15]

pointed out a way to relate the inclusive cross sections to three-body elastic

amplitudes. -.-...

Assumptions for the latter are thus conveyed into predictions for the experimental-

ly available inclusive cross sections. Thus assumptions on dominant exchanges at

asymptotic energies, e.g. gives predictions for limits of distributions. Such

scaling properties will be discussed later for our inclusive reactions. 16

The question if it is possible to separate out the behaviour of a part of a final state (factorization) could also be treated in the framework of the Mueller formalism. We have especially discussed the "fragmentation" of the target proton into a lambda hyper on. The beam proton collides with the target proton in such a way that the latter breaks up into fragments, among which a lambda is found. Schematically this proton induced fragmentation process, often de- noted, following Yang

p could be —^"Ti^^I or following the n - A visualized | p"*^ Mueller-Rsgge- formalism

But we could as well have used a K beam

K+ p - A visualized * j \^Z-\~ or following the . Mueller-Regge- formalism P

If factorization holds, the properties of the lower vertex could be separated out

from the zest of the reaction. As the lower vertex is the same in both reactions,

the ratio between the pD and the K p A-inclusive cross sections can, under cer-

tain circumstances, be simplified to a ratio between the properties of the upper

vertices. This ratio in turn, is related to the ratio between the respective total

cross sections.

Finally I would like to make a short remark on the technique used. In elementary

particle physics two main techniques are used today: Bubble chambers and

Counter systems. Some advantages and disadvantages are listed in Table 1. For

studies of neutral decaying particles such as K and A, the Bubble Chamber is

a superior tool. 17

3. EARLIER STUDIES OF PROTON-PROTON REACTIONS

As the present thesis mainly deals with the inclusive and semi-inclusivei aspects of proton-proton reactions, I will in this section concentrate on such studies.

In Table 2 is compiled important data on existing Bubble chamber experiments of the inclusive type studying strange particles in the final state in pp-reactions.

A thorough compilation of references to articles dealing with strange and non- strange particles production (Bubble chamber experiments as well as Counter studies) is given by Antinucei et al. [16],

Early studies of strange particle production in pp-reactions, mainly of the ex- clusive type in the momentum range 3.67-24,5GeV/c are listed by Nilsson [17] and Dunwoodie [18]. This list covers publications up to 1968.

Information on papers containing data for non-strange final states in pp-colli- sions betwen 3.7-300 GeV/c, used for charged multiplicity distributions, is compiled by Wrdblewski [19].

References to IT production work are given by Kaiser [20] *). Other particle production experiments are listed as well. Also Amrfibsov et al.compile' results from important experiments [21],

*<) Se alsoRef. [39].. . . 18

4. EXPERIMENTAL PROCEDURES

Exposures at the CERN 2 meter Hydrogen Bubble Chamber (2 HBC) took place

at four different occasions during the years 1966-1969.

Number of pictures Beam Batch Period exposed name

A Sept. 1966 20 000 U3 B Jan. 1967 80 000 U3 C Jan.-Febr. 1969 225 000 U5 D May-June 1969' 204 000 U5

Batches A and B were used for studies of the non-strange final states (Paper 1:1)*).

For the study of strange particle final states, all pictures were scanned twice

using view 1. The Stockholm part of films was measured on manual machines

of the type ENETRA. The equipment wa3 connected on-line to a CDC 8090 com-

puter. This improved system, described in Paper in :1, was used for measure-

ments of the dominant part of the films. The data from the measurements were

processed using the CERN program chain REAP-THRESH-GRIND-SLICE-SUMX

which was run on a CDC 3600 computer- Figure 2 shows the main steps in the

processing of events.

For batch C and D, a study of measurements of beam tracks every 50rth frame

revealed a significant discrepancy between the nominal beam momentum

(19.03 ± 0.10 GeV/c in batch C and 19.19 ± 0.10 GeV/c in batch D) and the

*) Information of relevance for the experimental treatment of batch A and B is given in References [1, 22 and 23]. 19 measured values ranging from 18.5 to 20.5 GeV/c. This spread should be. com- pared with the measurement error of BS 150 MeV/c s obtained from repetitive measurements on one beam track.

The discrepancy could be due to errors in the geometrical reconstruction iit space, to problems related to film handling (either at the exposure, the development, or the measuring stage) or to turbulences in the chamber liquid.

The varying non-linear effects appearing as spurious curvatures on tracks, are not taken care of by the reconstruction procedure.

We have devised a method to correct for the non-linear effects at a later stage

in the processing procedure.

We calculate for each 750-picture sequence the spurious curvature (1/P) _

by comparing the curvature of our measured beam tracks (1/p) . and

the nominal beam curvature (l/p\ . , v ^ nominal

*^^spurious J '^nominal,.~ \ '^'measured (6)

The "spurious curvature" is used to correct measured curvatures for charged

tracks in GRIND. Details of the procedure are found in Paper 11:3, in which

aiso other information concerning the experimental aspects arc given.

To obtain the cross sections, corrections for scanning efficiency and measiire-

1 ment efficiency are applied to the observed number of events. V• o s too near.

the main vertex as well as events outside the chosen fiducial volume are dis-

regarded. This procedure gives-cross sections "seen in ths chamber (fiducial 20 volume)". Such cross sections have been established for events in which one and only one V° is detected (a A or a K,,), and for events in which 2 V ' s are detected, corresponding to the classes K A and K K .

Weights were applied to these cross sections for the geometrical cuts (of V's de- caying too near the main vertex and for decays outside the fiducial volume), and also for neutral decay modes. We have in the calculations considered possible overlaps between the class of one detected V and the ciass of two detected V ' s.

Special formulae were derived. A correction for losses due to scattering of the V° before decay was also applied. After weighting, we obtain the

cross sections for strange particle pair production in the following cases:

(K°K°) (K°A) and (K A). The inclusive A and K° cross sections are ob- C=+l, o tained as well *). The Stockholm group has also given E cross sections. An estimate of the total strange particle production cross section is also given after corrections for the production of more than one strange particle pair and of H production.

The total sample of events used for strange particle production investigations is

Type Collaboration sample Stockholm part

A 4756 1387

Ks 4190 1048 K°A 531 203

210 92

Z+ 143 143

z~ 46 46

*) For these, the influence on the cross sections, from the production of more than one strange particle pair has been considered. 21

5. RESUMES OF PUBLICATIONS BELONGING TO THIS THESIS

Paper I;l General features

In this paper various general features of the proton-proton reactions at 19 GeV/c are treated. Attention is mainly devoted to the study of non-strange final states.

It was found that the average number of positive and negative Mean particle multiplicities particles are

= 3.01 ±0.01 (7)

=^ 1.01 ±0.01 (8)

Disregarding everything else in the final states but nucleons and pions, n_

could be identified with the number of negative pions, giving ,. ;, :

s= 1.01 ±0.01 (9) if

(a ) is then made up by the average number of protons (n ) and the average number of positive pions (n +).

(n > + (n +> s = 3.01 ±0.01 . (10)

Using thermodynamical model calculations of Hagedom and Ranft [24 J-to extra-

polate counter data to the whole of phase space, a ratio between the ff arid it

mean multiplicities Was found: • .•••-•• ;

... ",:., = 1.58 ± 0.05 •

From Eq. 9-il we deduce

. = 1.60 ± 0.05 „ . (12)

IT •• •.••''.'••'

(n >=1;41 ± 0.05 . . W) 22

Based on the observed frequency of electron pairs associated with the events

and on the assumption that the ir emission spectrum resembles in energy and

direction that observed for the negatively charged particles (assumed to be

iC s), it was found that

± 0.1 (14)

The mean inelastic proton-proton reaction is thus decomposed into

, ,. - 1.4 p +0.6 n + 1.6 n+ + 1.4 ff° + 1.0 if (15) w inelastic r v '

Correlation The mean number of ff s ((n ,> >) per inelastic event was found not to vary

much with the number of charged particles in the final state.

Charge The mean charge multiplicity is found to be Multiplicity Distribution (n . ) = 4.02 ± 0.0? . ch (16)

The inelastic production cross section was studied as a function of prong num-

ber as is given in Fig. 3. The distribution was compared to the results from

a IT p experiment at 16 GeV/c which gives a similar behaviour [25], A

Poisson distribution was given as comparison. An agreement was found

within errors. •

The momentum spectra of negative particles (ff~) are given for 4, 6 and 8 prong

events. The distributions for the transverse momentum component, (p ) and the

cm. longitudinal momentum (p ) are presented. Fits were given to the distribu-

tion formulae: -pI/D W(pL) (17) 23

) - NTpTe (18) for the different prong classes separately, where A, B, a and D are constants

and NT and N_, normalization factors, XJ 1

Poor agreement *vith factorization of longitudinal and transverse momentum parts was found. Whereas the projected distributions (17) and (18) separately gave good

fits, the product W(P ) W(p ) does not fit the two dimentional distribution to the lj X same high degree.

Paper 11:1

This paper mainly deals with the inclusive Ko and * A features from our proton- proton experiment at 19 GeV/c. It also provides inclusive information on the

TT. production. '' ~. ' ••*.•.•• •> ••; ---, •.••,••• is-'- .-•••• • •••• •-• . ••• •- -•

The prong number distribution for the combined neutral strange particle, sample

is given and compared to the total sample of inelastic events. One tendency

wMch was found is that the production of a K. or a A in an event slightly re-

duces the number of charged particles in the event from

in the total sample to

tailed studies.on the.multiplicity distributions areiound in Paper. 11:2., In .the '

latter publication are also found .estimates on the integrated.cross sections tor

strange.particle.;production. using.a.refinedianalysis technique and less, assump-

: tiono than, in Paper II:i...... : , . . ., ,. . ::••• - -"''•'. 24

In paper 11:1 the differential Lorentz invar.-..nt cross sections are given for ir , K and A : in longitudinal J E — dp,,, versus x = — (19) direction: °T Po ' ' x p

in transverse 1 r> _ d cr , 2 — E — dp versus p^ (20) direction: a^ J , , 2 *LT ^T v '

where o_ = a normalizing constant equal to the total pp cross section at

19 GeV/c (39 mb), p = the cm. momentum of the incoming protons (maximum proton momentum in cm.). PT = is the cm. longitudinal momentum and p is the transverse momentum component of a particle with total energy E in the proton-proton cm. system.

Fig. 4a-c shows the invariant x-distribution for ir , K and A. Fig. 5a-c o 2 shows the corresponding invariant p -distributions. The average values of the transverse momentum for n , K and A are

= 0.316 ± 0.003 GeV/c (21a)

<.p_(KJ> = 0.406 ± 0.005 GeV/c (21b)

Instead of x as longitudinal variable it is possible to use the rapidity y de- fined as

1 E+PL y = - In * (22) 2 E-pL 25

The normalized invariant cross section -2- as a function of the o m raoidi- H °T dy • cm ty y is presented in Fig. 6a-c.

The distributions are discussed in the frame work of a two-fireball thermo- dynamical model based on the work of Hagedorn and Ranft [24].

Further it is shown that the transverse and the longitudinal momentum compo- nents do not factorize well.

Paper 11:2

In this report we give cross sections for strange particle production in 19GeV/c

proton-proton reactions. The data is split up according to the various prong numbers (the number of charged secondaries) and according to the type of

strange particle pairs in the reaction. Values for the inclusive A and K pro- S duction is given as well.

The multiplicity distributions for events in which strange panicles are pro-

duced have been studied. The discussion is heM in the framework ol the KNO

(Kobp-Nielscn-Oleson) formalism ~ i "•*~ which has been modified ard shovn to

hold for overall inelastic: reactions at lower energies by Hurss, Uias dp Deus

a.iiti M011cr •_?•

K^ is lietecioci '). However, in some special fiasos. as for events in which a

AK pair is produced, the disiribuMon is more narrow as compared to what

is predicted from the modified KNO distribution.

*i This was earlier r.hown ~;>0~ u> h.Id down to an incident momentum <>:" ~>0 C,e\'/?. 26

Paper 11:3

The main results in this report have been given in paper 11:2 in condensed form. Thus paper 11:3 has the aim

— to give e\perimental details from the experiment, most of which has not

been given elsewhere

— to present some derivations of formulae used in the extraction of the

cross sections

We give a description of the formulae bringing "seen cross sections in the

Bubble Chamber" for observed 1 K_, 1 A, KOKO and Ko A over to cross o o o a sections for semi-inclusive production of (K K°)„_.,, , K A and K A pairs.

Also the treatment of the production of more thai) one strange particle pair in a reaction is presented.

Cross sections obtained are given in Table 3 (collaboration data). 27

Paper 11:4 Factorization in the inclusive reactions pp - Ax and K p -» Ax

The hypothesis of factorization leads to simple relationships between differen- tial cross sections for inclusive reactions such as those studied by us

pp -• A + anything (23)

K p « A + anything (24)

If in the inclusive reaction

a + b -* c + anything c is in the fragmentation region of b, then by assuming that the Pomeron and leading meson trajectories factorize, the Lorentz invariant inclusive cross section may be written

2 = y (M2/s 4) + due to 25 l ^ \\ bc (^trfcott™ < > ' meson exchange) where s is the total c'.ni. energy squared;' t is tHe momentum transfer

squared from b to c and M the missing1 mass recoiling 'against c. The three

particle scattering amplitude whose forward discontinuity in M leads to equa- tion (25), is schematically represented by

ii-^-d

P.OC 28 yP'1 is the value of the residue function describing the upper vertex in the case a of forward scattering. For difierent choices of particle a. for example p or K ,

y is related through factorization and the optical theorem to the corresponding a total cross section for particle a interacting with target b.

If the reaction abc is exotic and be nonexotic, the early scaling hypothesis [27] implies that the meson exchange part of equation (25) need not to be con- p sidered to first order. We then have, as y,— is the same for both reactions (23) and (24):

2 . 5Td(M2/s) *• -A> "TOT1""

dTd(M% * "* A)

In order to test the factorization hypothesis, the t-distribution for reaction

i K is com are( to tne (23) weighted by £ o TOT ( P)/O>T0T(PP) P ? '• distribution for reaction (24) (the factor j$ arising since for reaction (24) we must consider the

fragmentation of only one of the initial state protons).

The ratio R between the two sets of weighted t-values defined above should,

if factorization holds, take the valu--> 1. In the pp-reaction the two cm. hemis-

pheres are symmetric. Thus two s ltly different R-values could be obtained,

using folded or unfolded K p data for comparison. The two cases are in some

way two extremes and are shown in Fig. 7 a and 7b.

For our two reactions we conclude that factorization is satisfied at least to a 25 % level. 29

Paper 111:1 A hardware system for measurement of Bubble Chamber pictures on-line

The measuring of bubble chamber films in the Stockholm group.was earlier performed on two manual machines (ENETRA). In order to increase the quality of the measured events and to increase the measuring rate, a group started !n 1968 to construct a system to connect the measuring devices to a computer CDC 8090 (8 k, 12 bit words). Construction and testing of the hard- ware for the first ENETRA were finished in 1970. Since 1971, it has been used for the measurements of the pictures for the strange particle experiment as well as for other experiments. The on-line system, later extended to two ENETRA units, was used during the experiment 50-60 hours per week and the measuring rate was about 2.5 events per hour.

The main features of the system are shown in Fig. 8a. The typewriter of the off-line system has been replaced by a set of thumb wheel switches, the "data- box" and a number of "demand" push-buttons. The computer communicates with the operator via the "label display" and "signal lamps" (the "o.k.", "wait" and "error" signals) which are placed in front of the operator and via the "specif- ic messages", (Fig. 8b). The computer tells the operator which track or point to measure next, tests the results of the measurements and if necessary asks for remeasurements or complementary data. When the measuring of an event is finished the result is written on a magnetic tape in such a format that it can be used as an input to the program THRESH.

The software sysi.em has been, described elsewhere L28]. • . 30

The experiences of the on-line system in production has been

— The system is very easy for the operators to use. This was one of the

design goals.

— The measuring rate and the quality of the data has been increased

compared with the old system.

— The magnetic tip: unit or the output system of the data has been a weak

point.

— The limit of speed in the overall system is set by the speed of the

measuring table. 31

6. DISCUSSION ON SOME PHYSICAL ITEMS RELATED TO OUR INVESTIGATIONS

In Section 5 a presentation was given of each of the papers included in this thesis. In this chapter the aim is a) to further develop subjects introduced in the articles b) to make comparisons with experiments at other beam momenta c) to present investigations, made by other authors, of importance for a

broader understanding of our own results. In many such cases our results

have been part of the set of experimental data which have been used.

Whenever this has been the case for a quoted article we will explicitly

point out this fact.

The line of presentation of different aspects in high energy phenomenology we

shall use, is to start with quantities which are integrated over many vari- ables, as the overall cross sections and mean multiplicities. Next we discuss prong number distrioutions and close by discussing inclusive momentum spectra

and their scaling properties.

G.1 Integrated cross sections

In Papir 11:2 we showed, using our 19 GeV/c data as well as results from experi-

ments performed at neighbouring incident momenta, how the strange particle

production cross section rises monotonically up to 25 GeV/c (Fig. 9) from

0.18 = 0.03 mb at 3.67 GeV to -J .3 =0.3 mb in our 1B.0 GeV/c experi-

ment. Fig.10 a and b show the cross section versus incident momentum (p ' ) 32

o —o Inclusive for the inclusive production of A and K (or K ) respectively Reactions pp - A + anything (27) *

pp -. K or K + anything . (28) * *

Here we have used existing world data (Table 2) on inclusive production of

neutral strange particles. In both cnses the rapid rise from threshold of the

strange particle production is demonstrated; Aincreasing a factor as 3.3 and

K +K increasing a factor a> 17 between 12 and 303 GeV/c incident momentum.

As a comparison, especially as the K is a neutrally charged meson, we also

give (Fig.ll)the inclusive TT distribution versus p Ali. The 19 GeV/c point is

obtained from Paper 1:1. Also here we find a large increase in the cross section,

rising from RJ 40 mb at 19 GeV/c to sa 130 mb at 300 GeV/c incident momentum.

It is also worth noticing1 that the production of neutral pions is a factor « 17

larger than the production of neutral K-mesons at 19 GeV/c. At 300 GeV/c this

ratio is reduced to the order of =» 6.

Semi- inclusive Another way of showing the increase in the production of strange particles with Reactions incoming beam momentum is to split up the total production in one KK and

and one YK part and study their energy dependence separately. In paper

11:2 such a separation was performed at 19 GeV/c. Fig. 12 a and b show our

compilation of existing world data for the KK and YK pairs as a function of

!y. \n- We conclude that the YK mode is dominant in the region studied (up 1 -A H to =a 25 GeV/c.

*) By A is meant A or I , • •) Inclusive cross sections given in the form (K°) have been multiplied by 2. s 33

We also show the AK part of YK (being « 60 % at 19 GeV/c) as a function of

p . (Fig. 13 a) and demonstrate it to have the same general behaviour as YK.

In n p and 1t p reactions [29] the YK cross section has been shown to level

off already before 20 GeV/e incident momentum (Fig. 12 c).

Earlier this was believed to be true also for proton-proton reactions. Berger,

Oh and Smith [30] found the AK cross section to vary little between 13 and

28 GeV/c incident momentum (Fig. 13a).*)

As has been remarked by Morrison [31 j, this behaviour is in contradiction to

the rising A inclusive cross section up to NAL-energies.

We show, using our data at 19 GeV/c as well as the data from the Bonn-Ham-

burg-Miinchen collaboration at 12 and 24 GeV/c (for details see Table 2), that

the AK cross section rises in the region 12-24 GeV/c (Fig. 13 a).

A comparison between the results found by Berger-Smith and Oh for the KK

cross section and our i9 GeV/c results as well as other world data is also

shown (Fig. 13b).

*) It is in this connection of interest to point out that Berger, Smith and Oh used a different set of assumptions than was used by us in the derivation • of these cross sections. ' : • • ' " 34

6.2 Average multiplicities

In Paper 1:1 average numbers for the production of various types of particles

Average were established. The average numbers of produced pions were found to be Multiplicities = 1.01 ± 0.01 (29a) IT

where n + , n _ , n o are the numbers of n , it and V 's produced, respec-

tively.

From Paper 11:1, 2 we get the corresponding figures for K and A

(nK0+-0) = 0.08 ± 0.01 (29d)

(n.) = 0.062 ± 0.003 (29e)

Countei data at 19 GeV/c [32] gives as a comparison *)

= 0.036

Multiplicity There exist some theoretical predictions for such multiplicities. In the frame- Relations work of the multiperipheral model [33] the multiplicities increase slowly with in-

creasing energy. In particular, all the pion multiplicities (n +), (n > and

(n _ ) become equal if the total energy tends to infinity [84].

*) Errors are of the order 10-15 % as given in Ref. [16] where the multiplicities are derived from the data given in Ref. [32], 35

Obviously we are (according to Eqe. 29a-c) at 19 GeV/c still not at this asymp- totic region.

Lipkin and Peshkin [35] , using isospin arguments, have shown that for pure

isospin 0 t-channel exchange in pp interactions, inclusive pion production

satisfies the relation

2

for all pion mcmenta and thus also in an overall sense

2 " + ^V* (31)

being consistent with our data above (Eqs. 29a-c).

Also Honerkamp and Mutter [36] deal with the question of isospin relations

between the number of produced neutral and charged pions in reactions like

A + B -• n + + n _ + n « + (anything except pions) (32)

They find lower and upper bounds for 7T multiplicities in terms of ff multipli-

cities. For proton-proton reactions they get

in good agreement with our 19 GeV/c data (Eqs. 29a-c).

M. Bardadin-Otwinowska et al. [37] show that experimentally over the whole Multiplkitiet

.-...-•. -..-...... •;•••••.. V. ..:..:: •.-.:•:;• • •'. . •• •"• .[ Vef8US PLAB cm. energy range (3 < /¥ < 55 GeV)*' the average number of charge pions

*) Corresponding to 2 < PL»B < 1500 GeV/c incident 36

{a ) is within errors equal to twice the average number of It ' s both for Wch pp- and 11 p reaction

s + M 2 (34) ch

Among other data our values at 19 GeV/c were used (Paper 1:1) to draw this conclusion in the pp case.

The dependence of 'n > on p (giving approximately versus pT ) LAB v JjAiJ was studied by Ming Ma et al. [38] for proton-proton reactions. Our data (from

Paper 1:1) is inaerted for comparison in the table below:

Plab GeV/c

13.0 0.83±0.02 18.0 1.02±0.02

19.0 1.01±0.01 OUR EXPERIMENT 21.1 1.15±0.02 24.2 1.24±0.02 28.4 1.30±0.02

In a study by M. Antinucci et al. [16] the average multiplicity of various

particles (as 7T , IT , K , K , p and p) was calculated and compiled as a

function of s (the square of the total CM energy) up to ISR energies. Fig, 14

fetched from this paper shows the s-distributions for various particles in 2 the final state. The data given for s =37.4 (GeV) corresponding to 19 GeV/c

incident momentum have been taken from our Paper 1:1 concerning the

quantities , (n > and (n_o) (where n stands for the multiplicity

of protons). 37

The energy dependence of the multiplicities is predicted by most theoretical models to be of the ln(s) type in the asymptotic region, while at low energies povver dependences of the form s are expected.

In order to be able to give a fit to the whole energy range studied, Antinucci et al. [16] combined the ln(s) and sa functions thus

+ = A+Blns+Cs"' (for if, v , K", K ) (35a) 1/P — (n,) = A1 +B'lns + C's ' J In s (for p and p) (35b)

(dashed lines in Fig. 14) where A, B, C, A', B', C are constants.

The following remarks of interest in combination with our data could be

extracted

(i) (n +> is larger than - The difference between (n +) and 6i _>

is constant («a 0.6). Thus the per centage difference is decreasing with

+ _ • increasing energy. The same trend exists for K and K (with a difference wO.l)...

ii) The proton multiplicity has a small energy dependence, which could be

considered typical of a leading particle.

Lii) Except for the proton, the increase of multiplicities atlow energies is faster

;; : .-than :a in(s), behaviour. This might be.explained as a "threshold effect"i

We plot and as a function of pT in Fig. 15 a and b usingavailable world data [ [39] and Table 2], It ia seen that both increase;, the'meaii ff • multi-

plicity 'increasing a factor of w3 and (n o) a factor of «a 8 between. 1'9 and :'..

; ; : r •'"•:'••-J *:••:' •••:•• •-•••••• .'••- v- " ••••••' ••-.•^••- •:: \/•-:•}: "< -r:'\ );•:•:• : •'':.';•: ''"•'•. 300 OoV/c"incident momentum. The moan A multiplicity rises in the same.: 38

momentum interval a factors 2, However, one observes a flattening off in the

NAL energy range as could be seen h\ Fig. 15c. This should be compared to

the proton multiplicity behaviour already shown in Fig. 14.

(n 0> In Paper 1:1 it was observed that (n^,) does not vary much with the number 71' versus n of charge particles in the final state,

Several authors have studied this question at various beam momenta.

Mi Bardadin-Otvvinowska et jal. [37] compiled results from pp reactions

(using our data at 19 GeV/c to show the "PS-energy range" behaviour) as well

as from v p reactions.

If a linear parametrization is done

(n^) = cm_ + P (36) .

the slope a is soen to increase with increasing incident momentum. A model-

was worked out based on the Czyzewski-Rybieki formula for the distribution

of particles produced [40] and on the hypothesis of isospin independence [41].

The same dependence has clso been discussed by Dao and Whitmore [42], who

presented data from an extended sample of beam momenta. Again the 19 GeV/o

data are ours. In Fig. 16 a we have added data from the 12 + 24 GeV/c and

102 GeV/c experiments [39a, 39f ]. Whereas the average number of ir°'s

produced in pp collision does not depend on the number of associated oharge

particles at lower energies, this is not true any longer at highor energies. 39

Dao et al, [42] have compared the corresponding features for Ko using the ("Vo*

303 GeV/c data and those obtained at 205 GeV/c (References in Table 2). In versus n^

Fig. 16b we have extended the comparison to the whole range of energies from

12 GeV/c up to 303 GeV/c showing versus n . We find the same S general increase of the slope av0 for K° (Fig. 17b) as a function of pTLAB iv_S n - a i as for rr s (Fig. 17a). However, the cross over of the slope parameter a

from negative to positive values occurs at a higher energy for Ka, This is in

agreement with the comment of M. Bardadin-Otwinowska et al. [37] stating

that the slope a is a measure of the available cm. energy. Thus in the !£„

case, where we have produced a heavier particle than a IT , the energy avail-

able to produce other particles is somewhat reduced as compared to the u case,

with a delayed rise of the slope a as a result.

In Fig. 16 c the corresponding behaviour for A is compiled for incident mo- versus n_ menta between 12 and 205 GeV/c. In Fig. 17c the fitted slope.parameter

a. is given as a function of p . It is interesting tp,observe a possible rise

alsoffor a. as a function of p _. The change to positive O'-values occurs .-. -;.. •, • •--...• ;.••.•. • •< ... ' • ::. .' •:.:.~ •*;.'; ?•;' '!K;i;r? ki \'.ih-. ii.-»i-:;*4e>>j; •••'•£>< -I*

even at a higher beam momentum than for K,,. ft would bevinteresting'to know

what happens to the a_n -value, at low incident momentum (pT'A »,« 3 GeV/c),.

Has it the same general low energy trend.as has been found for a o and a. , ? : ' •'•• • • ' •;••'• ,••••'•. :•'. :•••• • I\ '• ' ••• ivn • •

6.3 The charge multiplicity distribution ..

The multiplicity distributions (i.e. the distribution of the production.cross sec-

tion; as a function of the number of produced, or charged, particles) have. :.

attracted interest a long time. But rot until the first yearij of 1970's,. when the.; 40

start of the accelerators in the 100 GeV/c region provided controlled experi-

mental facilities in the high energy region, more detailed information became

available from experiments using incident momenta up to 400 GeV.

In Fig. 3 our charge multiplicity distribution from Paper 1:1 is shown.

plicity for proton-proton reactions at 19 GeV/c. Paper 1:1 gives the value at

19 GeV/c to be

In Paper 11:2 (n , > values for events in which a AoraL has been detected ch S were given

(n U>A . = 3.81 ± 0.06 (38a) chA-events (n u^° * = 3.76 ±0.06 • (38b) ch K -events

As was pointed out in Paper 11:1 the existence of a strange particle in the reac-

tion thus tends to decrease the overall mean charge multiplicity.

The value of 4.02 for the overall sample has been used in the world compilations

presented in Fig. 18. Antinucci et al. [16] found for various particles (Chapter 6:2),

that a simple ln(s) dependence is not sufficient to fit the whole energy range.

The low energy region is better approximated by a power of s-function. This is

also true for (n , ). ch 41

Turning over to the question of the "width" of the distribution as defined by Dispersion the dispersion

2 2 1/2 D=((n > - ) (39) and plotting it as a function of the mean charge multiplicity for various pp experiments Wroblewski [44] found that experimental data in the range from

4 to 303 GeV/c (the 19 GeV/c point extracted from our data) are well de- scribed by the formula

D = A((noh>-l) (40) with A = 0.576 ± 0.008 as a best fit (Fig. 19). A similar linear relation was

earlier found for the then limited amount of data by Malhotra [45].

In Paper 11:2 we have investigated the question if events, in which strange

particles are produced, have a similar behaviour as the overall sample. Fig.

20 a shows that at 13 GeV/c this indeed is the case for the A and Ke inclusive

samples, respectively. As was pointed out in the beginning of this chapter the

average charge multipiicity for such events is somewhat lower than in the over-

all non-strange sample. A reasonable explanation for this behaviour is that the

available cm. energy in the reaction for charged particle production is some-

what diminished by the restriction that strange particles should have been

produced. And as we have observed in the non-strange case, experiment having

less c.m. energy have less (n . ) and falls lovrer on the D versus (n ^) line

(Fig. 19). •• • • . . • ••..: • ..- -•.-. -.: .• :••• ..".:.• :-;.;.: . . •••.. . v •/ 42

In Paper 11:2 we investigated this matter further and found that if we claimed a specific strange particle pair to be produced (a (K K )c_+1> a K A or a K A pair) then the dispersion versus the mean charged multiplicity for the three classes spread out on the D versus (n , > line, as is seen in Fig. 20b. It is worth noticing that whereas the spread along the line in Fig. 20 a is due to the variation of incident momentum, the spread along the line observed in Fig. 20 b is due to the selection of events at one and the same incident momentum. The observed spread suggests that the available energy for charged particle pro- duction is different for the three sub-samples. In order to investigate this aspect further, the mean energy for the strange particle part was subtracted from the total cm. energy . The remainder system so obtained can also be considered to have quantum numbers, being the difference between the initial ones in a proton-proton collision (charge = 2, baryon number = 2, strangeness = 0) and those of the strange particle part. In Table 4 we give the quantum numbers, mean energies and the average charged multiplicity for.the remainder parts to

(K K ) , K A and A corresponding to the quantum-numbers of a pp, ff'p and C— **" 1 K p system respectively. In Fig. 21 a-c we present the mean charge multi- plicity versus beam momentum for these three initial states. Our values for the remainder systems are shown in the figure at corresponding beam momentum.

A reasonable agreement is observed between our calculated values for the re- mainder system and the behaviour of the corresponding reactions.

In Paper 1:1 we have used a Poisson distribution as a reference (Fig. 3).

The basis for the derivations of Poisson distributions for multiplicity distributions is the non-existence of long range correlations between particles. In order to get a measure of the non-Poissonian nature of a

•) C=^-l stands for the charge conjugation state +1. • •) Considering involved particle masses as well. 43 distribution, Mueller [46] devised higher correlation functions to express the deviation from an independent particle production.

The "second" Mueller correlation parameter f is defined f

2 f2 = (n (n-l)> - (41) where n is the number of particles produced in an interaction, f could be studied e.g. for negative particles (n = n ) or charged particles (n = n , ). en

Models exhibiting only short range correlations (e.g. pure multiperipheral models) predict f to rise as a simple ln(s) function.

Ammosov et al. [21] have plotted the f function for charged particles for world data, not only for pp-reactions (where our experiment is used at

19 GeV/c) but also for IT p, ff p, K p and K p reactions. a« a function of a

reduced cm. energy Q (j/s~ minus the different incident particle masses).

They find (Fig. 22 a) that f (being zero for a Poissonian) becomes positive

from about Q = 5.5 GeV corresponding to a laboratory momentum of s» 30 GeV/c

in the pp-reaction case. From there and above a considerable and increasing

amount of long range correlation is found.

In Fig. 22 b we show the corresponding, plot for events in which a K oral

has been detected. We find an increase of i,, as a function of Q in this- case -

as well, but the onset is somewhat retarded as could be;expected from the re- ;

duced cm. energy for remaining particies when strange particles are created

in the event. . .

. . ; ; Multiplicity If we turn back to the multiplicity distribution themselves they are found to Distributions 44 exhibit the following characteristics as a function of cm. energy (\fs ) (or

Of PLAB): a) If the cross sectior for each prong class as a function of p . is plotted,

we find that for eseh prong class (except for the 2 prong class) the cross

section grows up to a maximum and then falls of. This maximum occurs

at subsequently higher beam momenta, the higher the prong number is.

Fig. 2? a shows this feature for the non-strange world sample; and in

Fig. 23b and c, we have plotted the same quantities for the inclusive K

and A samples in proton-proton reactions. We see that the same general

trend is visible in all three cases, perhaps with the maximum for the

Ftrange particle distribution shifted somewhat to higher p -values

as compared to the overall inelastic pp-sample.

b) The position of the maximum of the multiplicity distribution moves to-

wards higher prong number as s increases.

c) The width of the distribution broadens as s increases.

d) The mean value (n , ) of the distribution increases with s . ch

If thus for each energy the normalized prong number cross section a (s)/a(s)

is plotted as a function of the prong number and then a smooth curve is drawn

through all the points belonging to the initial cm. energy e., e , and e ,

respectively, we get a figure of the following type

^> prong number (n) 45

If instead of a (s)/o(s) we plot the quantity

C (s) K i^ <42>

as a function of

(43)

all curves will practically coincide. This behaviour is the KNO scaling. The

name is due to the initials of the physisists suggesting this feature (S. Koba,

K.B. Nielsen and P. Olesen [13].

Scaling as a general concept means that a certain distribution l/)(z,s), being

a function of a non-energy dependent parameter z, as well as some energy

parameter /if, sooner or later becomes energy independent ("scales")

(44) s-oo

The shape of the distribution thus converges to a fixed one independent of

energy. If this happens at accelerator energies and not in a far off "asymptotia"

(s = oo) we talk about "early scaling".

The derivation of the KNO scaling rn'.e (see above) was based on the assump-

tion that another scaling should hold '- that of the inclusive longitudinal

momentum spectrum in the form of Feynman scaling [11 a]. We will return'

to this question once more discussing the momentum'spectra in Section's.'4; •"

Slattery [47] and Olesen [48] showed, using world data for proton-proton ! reactions, that the KNO scaling holds well already for the energy range 46

50-300 GeV/c. Plotting 4> as a function of z all the data points lie nearly on

a single curve (Fig. 24 a).

At lower energies, Slattery [47] found a significant discrepancy as compared

to the KNO prediction using our 19 GeV/c data from Paper 1:1 and the ones

from 28.5 GeV/c [49], (Fig. 24b).

It was, however, possible to extend the KNO scaling down to lower energies

as well, as was shown by Buras, Dias de Deus and Miller [26], introducing

a simple correction in the KNO formula now taking the form

(M -a) a - > #'(*•) (45) inel s -• OD

with

zT = ,n 7 ° (46)

where a is a phenomenologically introduced parameterwhose value depends

on the initial state and is equal to 0.9 for proton-proton reactions.

Turning to the strange particle events, Cohen [50] showed, following the

procedure of Slattery's that KNO-scaling also holds for events (above

50 GeV/c incident momentum) in which neutral strange particles had been

detected. In Paper 11:2 we extended this result down to 19 GeV/e using the

Buras-de Deus-M(i(ller KNO modifications. Fig. 25 a, b give our modified KNO-

multiplicity distributions for the K^ and A inclusive samples and we ohserve a

good agreement. 47

However, plotting the modified KNO prong distribution for the events in which a (K K 'n_ , (K A) cr a (K A) pair is produced respectively, we found certain

K K differences. Whereas the ( ° c_+1 and (K°A)-pair events reasonably follow the modified KNO-behaviour, this is not so for the (K A)-pair events as is seen

in Fig. 25 c, d and e.

6.4 Scaling properties ; momentum spectra

In 1969 Feynman [11] suggested that for inclusive reactions at high energies

(the asymptotic limit) the invariant cross section distributions f should scale

towards a cm. energy independent distribution f

(47)

where

P* 2P* p. S->QO yfs max

(where p is the londitudinal momentum in the overall cm, system: p^ ' max is the maximum value kinematically allowed for this reaction, and v^s is the

cm. energy).

This scaling law was based on an analog)' to Bremsstrahlung. A particle (e.g. a

proton) passing through nuclear matter (e.g: another proton) radiates particles.

This has later been called "pionization'1. in addition the original particle may

fragment into a few particles• • .• ; - .•• ..•••-.• 48

Yang and coworkers [12a] suggested a scaling behaviour for the fragments of the leading particles *). In their scheme, investigations on the scaling behaviour for p or p should be done in the rest system of the target (target frag- mentation) or in the rest system of the beam (beam fragmentation). The cor- responding scaling law is called the "Hypothesis of Limiting Fragmentation".

A great interest has, since these suggestions appeared, been devoted to check the existence of scaling for various reactions and particles.

The variable x is well suited to analyze the distributions of secondaries, which are relatively slow in the rest frame of either of the initial protons

(the so called fragmentation region). However, for the distribution of second- aries which are relatively slow in the cm. system (the so called pionization region) it is less well suited.

Here the rapidly y already defined in (22) as

1 E+PT = ln y 9

*) It is worth observing that Yang and coworkers do not abolish the possibility of centrally emitted particles, or to quote Yang [12b], "There may or may not be other particles emitted in addition to these two bands of fragments1." It was emphasized thnt the hypothesis limiting fragmentation is independent of the existence or nonexistence of pionization. 49

One interesting and useful feature we shall use below for a rapidity distribu- tion is that under a Lorentz boost along the collision axis the whole distribu- 1 1 + B tion is simply translated by an amount - In (-—e) [51] where 0 = p/E. 2 1 - p First let us consider central production of mesons (presented in Paper 11:1). Central Region Production in the central region (|p* \< 0.1 p* where p is the incident Lt 0 0 momentum in the cm. systems) is most suitably studied in the cm. rapidity cm variable y . The invariant cross section for piop production in the central region is known to rise substantially as the energy increases [52].

In our region this was studied by Michejda [53]. Comparing the 12.9 and

28.4 GcV/c pp-data [54] to an empirical parametrization of the 19 GeV/c data [55], he finds an increase of the cross section with increasing beam momentum for x =s 0.

A central plateau is known to develop at energies above 100 GeV/c with an in- creasing height of the central plateau as found by the British-Scandinavian

ISP. Collaboration [56], In Fig. 26 a we show the invariant normalized distri- bution —— versus the cm. rapidity y for 1T~ at various incident momenta between 19 and 205 GeV/c. No plateau has developed yet at 19 GeV/c. but a .

possible plateau is starting to develop at 69 GeV^o [57]. The scaling limit if,

not reached at 19 GeV/c. The approach to scaling is frcni below. • • : :

The corresponding distribution, for. K is. presented in Fig. .26Ij in which-we,.

also have plotted the data from, the 102 and 303 Gey/c experiments .(Table; 2)*;

At our energy no central plateau has developed,, F.;T. Dao et al. [Table, 2 and

[39hj] claims at 303 GeV/c that "there Is evidence for a plateau with width of 50

CHI

two units in y". The scaling limit as studied at y = 0 is not reached at

19 GeV/c for K . The approach to the limit is from below.

Fragmentation Now let us turn to the fragmentation region (beam-fragmentation p£ > C. 1 p ,

Region +

target-fragmentation PT 4 -0.1 p*). The behaviour in this region is well de- scribed by the Feynman x-variable (except for values close to |x| R* 0) or the

yCm rapidity 9hifted along the axis of the colliaion to the rest system of one

of the incident protons (e.g. to the target proton giving the rapidity in the lab laboratory system y ).

In the Mueller-Regge formalism the approach lo the scaling limit is expected -1/2 to follow a s dependence in the fragmentation region. This rate of approach

is quicker than the rate predicted in the central region (s * dependence) [27, 58

59, 60].

For inclusive n production the scaling limit is reached already at PS energies

as is shown in Fig. 27a. The yla b distributions from experiments covering a

wide range of incident momenta between 12-205 GeV/c all coincide within errors lab - for y < 1.2. The scaling limit for ff is thus reached already at 19 GeV/c in the fragmentation region.

Comparing experiments in the ISR range [16, 61-64] with the data at 24 GeV/c

[65] such a scaling behaviour has been suggested for other particles as

well [31]. For K° Dao et al. [Table 2 and [39h]] claims that the scaling

limit has been reached at NAL energies. It is not possible yet to answer the

question if scaling is reached already at 19 GeV/c as is seen in Fig. 27b. the 51 statistics is still too poor in the high' energy range (> 100 GeV/c incident

momentum) to make any meaningful comparison between the distributions from that region and the one at 19 GeV/c in the extreme target fragmentation region

(ylab

For ADao et^l. [Table 2 and [39h]J claims that the scaling limit has been

reached at NAL energies. Comparing data down to PS energies, they claim that

the approach to scaling is quicker for A than for K . The approach is from

below.

lab We have plotted the y distribution for A inclusive production for 18 GeV/c

as well as for 12, 24 and 102 GeV/c data in Fig. 27c. The general level of

points for the high energy experiments is.above the one found for 19 GeV/o in

the fragmentation region, indicating that the scaling limit his not been reached

at PS-energies.

Further support of this judgement is given by the increase of a factor of sa 2

from 19 GeV/c to 303 GeV/c of the inclusive A cross section. However, as in

case of K , the statistical errors in the present set of data from the NA1,- o region are too large to make any definite: conclusions.

Scaling already at PS energies in the fragmentation region for H in pp-riiac- •••.-. Early :. . Scaling lions supports the theoretical prediction by Chan and oihers [27] that if the . . •

system (abc)... in the inclusive reaction .... .

a - b -* c •-. anything.. • •. • • . • . • ..• ••'..'.•'':• :\ .r'y: '••' : ... \ 52 is exotic, as the system (ppff ) is, and if simultaneously (be) is non-exotic, as

(pff ) is, then "early scaling" should be expected. The eariy scaling prescrip- tion is also valid for the reactions

pp - A +• anything (49a) and

K p - A + anything. (49b)

Both these reactions have been studied by us (Paper 11:4). The early scaling pre- diction makes it possible to assume Pomeron dominance [66], Using this assump-

tion, we have shown for reactions (49a) and (49b) that factorization holds within

25 %, as was earlier presented in Chapter 5. 53

7. SUMMARY

This thesis contains a large variety of information. In order to stress which results of ours I consider most important a summary is given below.

We have found that

A. The inclusive and semi-inclusive cross sections at 19 GeV/c are

o-(A) = 1.86 ± 0.06 mb

cr(K°) = i.27 3: 0.04 mb

a(AK) = 1.78± 0.06tnb

O(.YK). = 2.73 ± 0.23 mb

a (strange particles) = 4.3 ± 0.3 mb .

Comparing these cross sections with information from other experiments

in the energy region corresponding to 10 GeV/c •& p _ & 30 GeV/c we Li A13 conclude that all these cross sections rise in the entire PS-range. This is

especially true for cr( AK) which has earlier beeirticohsMerea to ievel off*

•below-30 fieV/c. •••.,-l .:;-•;:-p:r ^^ s--'^ ,:'."« '«•-., " v; '*lt*-&W*/£8t>K#^.:,

B. At 19 GeV/c the slope of \n~), of (n 0) and of versus the

number of negative particles in t!ie reaction (h ) is small in all

three cases

' '" 1t°i •0.'b6±0.l0 •'••••••-• •••••••_•:••• -••..•••

K°: -0.0099*0.0007 ; •.-. .. • .; • -. W '

••'•••;.••• ,A:! -o,oio-*-.o;oo2.'•:•••• •• - •' ": ••• r:'• • ••.;;lr'v";.'^';.;^'... .-• ! 54

Comparisons with the behaviour at other energies show, that the slope for

TT°, for K and for A increases as a function of incident momentum. The

cross over to positive values of the slope occurs at a higher incident

momentum for A than for K . o C. The multiplicity distribution of events in which a K or a A is found, or

a (K°K°) , or (K A)-pair is produced, follow the same modified

KNO curve as does the overall inelastic pp-sample.

Events in which a (K A) pair is produced do not follow the modified

KNO curve. ,

From the multiplicity distribution of events in which a strange particle

pair is produced the computed dispersion and mean charged multiplicity

have been found to follow the same linear relation as the overall sample

at 19 GeV/c. The datapoints falls however at different positions on the

dispersion versus (n , ) line depending on the type of strange particle

pair which is produced.

D. The Lorentz invariant differential cross section distribution in the cm.

rapidity variable y for K_ shows no scaling in the central region in

our energy range. The same feature is found for it . No central plateau

is found for any of them at 19 GeV/c. The approach to scaling is from

below.

lab - E. In the fragmentation region the invariant y distribution for ff scales at 19 GeV/c.

F. The form of the K momentum spectra resembles the one obtained for

ff-mesons. In the framework of a two fireball thermodynamical model 55'

both the spectra from Ks and IT could be described by the same tempera- ture T = 130° and the same Lorentz 7-factor (y = 1.2) corresponding to

the velocity of the fireballs relative to the cm. system.

The A-spectra were not possible to include in the same description.

H. Factorization holds already at our energies, at least to a 25 % level for

the inclusive reactions

pp -• A + anything

K p -• A + anything

w -4- i, _» where both (pp A) and (K p A)are exotic and (pA)non-exotic, suggesting

early scaling. 56

8. ACKNOWLEDGEMENT

Present day work in experimental High Energy Physics does not come into be-

ing if not powerful resources of different kinds are brought together. First of

all the carrying through of one single experiment needs a high rate of co-opera-

tion between many individuals. This is to some extent reflected by the number of

authors to the articles published. To all my co-authors in the Scandinavian

Bubble Chamber Collaboration I am grately indepted, especially as many have

been my teachers during the years but also because they have, to not a small

extent, provided the sphere of ideas from which this thesis was built.

First of all may thanks are due to Professor Gosta Ekspong who introduced me

into this field and since then has followed the progress of work with keen interest.

He has given me a glimpse of the rigour necessary for high class scientific work.

To Docent Narendra Yamdagni, co-author and my daily teacher and friend I

owe thanks for all knowledge and interest he has transmitted to me. Thanks

beyond words are also due to my other daily comrades and close friends since

years in the strange particle group, F.L. Per Olof Hulth, F.M. Kim Alpgard

and also to F.M. Frank Lovgren.

Thanks are also due to Docent Per Carlson, Docent Sven-Olof Holmgren, and

Docent Sigward Nilsson, Stockholm, for interest, encouraging discussions and

help of various sorts during years. In the Scandinavian Bubble Chamber

Collaboration I feel especially indebted to Dr. Anne-Grete Frodesen, Oslo,

Dr. Siv-Britt Ljung and Dr. Pilvi Villanen, Helsinki. 57

Necessary for a High Energy experiment is a scientific environment "above the critical size". I am most grateful to Professor G. Ekspong who has giT en me op- portunity to use the facilities built up under his guidance in the Stockholm group.

On the technical side I am indebted to F.M. Lennart Granstrom both as co- worker in the earlier stages of the experiment and later for the work he has put into the CDC 3600 computer. Thanks is also due to the operating crew of this machine,

Last but not least I am most grateful for the work done over ages in scanning- measuring etc. by our technical staff among which Mrs Marianne Holmberg,

Miss Kerstin Nelander and Mrs Siv Rosenqvist have been the key-persons.

For the tedious work of typing the manuscript I owe thanks to Miss Annita

Nasstrom and Mrs Git Sundt. Mr. Ants Paas has always provided me with excellent photographic material.

Finally I am deeply grateful to my dear parents for encouragement during

years. 58

REFERENCES 1 S.O. Holmgren, Thesis, University of Stockholm 1970, USIP- Report 70-08 (1970) 2 L. Le Prince-Ringuet and M. Lheritier, Compt.Rend. .219 (1944) 618 3 G.D. Rochester and C.C Butler, Nature 60; (1947) 855 4 R.W. Thompson et al., Phys.Rev. 90 (1953) 1122 and 90_ (1953) 329 5 A. Pais. Phys.Rev. 8& (1952) 663 6 For a review of the early history of strange particle physics see R.H.Dalitz, Repts.Progr.in Phys. £0 (1957) 163 7 VV.D. Fowler, R.P. Shutt, A.M. Thorndike and W.L. Whittemore, Phys.Rev. 9J. (1953) 1287 8 M. Cell-Mann, Phys.Rev. 92 (1953) 833 9 T. NakanoandK. Nishijima, Progr.Teor.Phys., (Kyoto) JJ) (1953) 581 10 M. Gell-Mann, Nuovo Cimento Suppl. 4, 2 (1956) 848 Ha R.P. Feynman, Phys. Rev. Letters 23 (1969) 1415 b R.P. Feynman, Proc. 3rd Int.Conf. on High Energy Collisions, Stony Brook (1969) 12a J. Benecke, T.T. Chou, C.N. Yang and E. Yen, Phys.Rev. 1,88 (1969) 2159 b C.N. Yang: "High Energy Collisions", Gordon and Breach Publ. New York (1969) 13 Z. Koba, K.B. Nielsen and P. Olesen, Nucl.Physics B40 (1972) 317 14 Z. Koba, Proceedings of the CERN-JINR School of Physics 1973, CERN Yellow report 73-12 (1973) p. 197 15 A.H. Mueller, Phys.Rev. D2 (1970) 2963 16 M. Antinucci et al., Letter al Nuovo Cimento (5 (1973) 121 17 S. Nilsson, The Nucleon-nucleon Interaction at High Energies; Herzeg Novi lectures 1968, Methods of Subnucloar Physics Vol IV part 1 (Gordon and Breach) 18 W. Dunwoodie, Thesis, University of California, Report UCLA-1033 (1968) 19 A. Wroblewski, University of Warsaw report IFD/5/73 (1973) and IFD/73/9 20 G.D. Kaiser, Daresbury report GIFT 8/73 (1973) 21 V. V. Ammosov et al., Nucl. Physics B58 (1973) 77 22 N.K. Yamdagni, Thesis, University of Stockholm 1970, USIP-report 70-07 (1970) 23 O. Danielsson, Thesis, University of Stockholm 1971, USIP-report 71-06 (1971) 24a R. Hagedorn, Nuovo Cimento Suppl. 3_ (1965) 147 b R. Hagedorn and J. Ranft, Nuovo Cimento Suppl. 6 (1968) 169 c R. Hagedorn, Nucl• Physics B24 (1970) 93 d R. Hagedorn and J. Ranft, Nucl.Physics B48 (1972) 157 25 Aachen - Berlin - Bonn - CERN - Cracow - Heidelberg - Warsaw Collaboration, Nucl. Physics B13_ (1969) 571 26 A.J. Buras, J. Dias de Deus and R. Miller, Phys.Letters 47B (1973) 251 27 H.M. Chan et al. , Phys.Rev.Letters 26 (1971) 672 28 G. Blomqvistand P.O. Hulth, USIP-Repoit 74-02 (1974) 29a S. Brandt etal., Phys.Letters 22 (1966) 230 b S. Brandt et al., CERN/TC/Phys 66-12 30 E. Berger, B.Y. Oh and G.A. Smith, Phys.Rev.Letters 28 (1972) 322 31 D.R.O. Morrison, CERN/D.Ph.II/Phys 73-46 (1973) 32 J.V. Allaby et al., CERN 70-12 (1970) 33 D.Amati, S. Fubini and A.Stanghellini, Nuovo Cimento 26 (1962) 896 34a L. Caneschi and A. Schwimmer, Phys. Letters 33B (1970) 577 b L. Caneschi and A. Schwimmer, Phvs.Rev. D3 (1971) 1588 35 H.J. LipkinandM. Peshkin, Phys. Rev. Letters £8 (1972) 862 59

36 J. Honerkamp and K.H. Mutter, Nucl. Physics B38 (1972) 565 37 M. Bardadin-Otwinowska et al., Acta Physiea Polonica B4 (1973) 561 38 Z.Ming Ma et al., Phys.Rev. Letters jH (1973) 1320 39 Inclusive 7r° data in pp-reactions a 12 GeV/c Blobel et al., DESY Report 73/36 (1973) H. Fesefeldt, Thesis 1973, DESY Fl-73/11 (1973) b 12.4 GeV/c J.H. Campbell et al., ANL/HEP 7311 (1973) c 19 GeV/c paper 1:1 d 23 GeV/c M. Fidecaro et al., Nuovo Cimento 24 (1962) 73 e 24 GeV/c see 12 GeV/c f 102 GeV/c UR 457/UMBC 73-20 g 205 GeV/c G. Charlton et al., Phys.Rev. Letters 29 (1972) 1759 h 303GeV/cF,T. Dao etal., Phys.Rev. Letters 3£ (1973) 1151 i 500 GeV/cG. Neuhofer et al., Phys. Letters 37B (1971)438 and 38B (1972) 51 1100 1500 40 O. Czyzewski and K. Rybicki, Nucl.Physics B4J7 (1972) 633 41 F. Cerulus, Nuovo Cimento Ij9 (1961) 528 42 F.T. Dao and J. Whitmore, NAL-Pub. 73/47-Exp. 43 G.H. Thomas, ANL/HEP report 7302 (1973) 44a A. Wroblewski, Proceedings of the III Int. Colloquium on Many-Body Reactions, Zakopane 1972 b A. Wroblwski, Warsaw University preprint IFD/72/2 45 P.K. Malhotra, Nucl.Physics 46 (1963) 559 46 A.H. Mueller, Phys.Rev. m. (1971) 150 47a P. Slattery, Proc. XVI Int.Conf. on High Energy, Physics Vol. 1 (1972) 238 b P. Slattery, Phys.Rev. D7 (1973) 2073 48 P. Olesen, Phys.Letters 41B (1972) 602 49 W.H. Sims et al., Nucl. Physics B41_ (1972) 317 50 D. Cohen, Phyg.Letters 47B (1973) 457 51 M. Jacob, Proceedings of the CERN-JINR School of Physics, Ebeltoft (1973) p. 7 52 T. Ferbel, Phys.Rev.Letters 29 (1972) 448 53 L. Michejda, Nucl. Physics B35 (1971) 287 54 D. Smith et al., Phys.Rev. Letters 23 (1969) 1064 55 H. Bfrfggild et al.. Nucl. Physics B27 (1971) 1 56 B. Alper et al., Phys.Letters 47B (1973) 75 and 275 57 E. Pauli et ai., Contribution 228 to thu Int.Conf. on High Energy Physics, Aix-en-Provence 1973 58 M.S. Chen et al., Phys. Rev. Letters 26 (1971) i585 59 J. V. Beaupre et al., Phys. Letters 37B (1971) 432 60 T. Ferbel, Phys.Rev. D8 (1973) 2321 61 M. Banner etal. (Saclay-Strasbourg group), Phys. Letters 4113 (1972) 547 62 The British-Scandinavian ISR group, Contribution to the Vanderbill Conf. 1S73 63a L.G. Ratncretal. (The Argonnc-Bologna-Michigan group), Phys. Kev. Letters 27, (1971) 68 b A. Bertinetal., Phys.Letters 38B (1972) 260 64 The CERN-Holland-Lancaster-Manchester group M.G.Albrow et al., Nucl. Physics B51. (1973) 388 No scaling indication for pp'r+K + anything 65 tf.V. Allaby etal., Nucl. Physics B52 (1973) 31G 66 II. Miettinen, Thesis, University of Helsinki 1973 67 a. 19 GeV/c Paper 1:1 and 11:1 b 24 GeV/c A. Brandt, Interncr Berictil DESY Fl-72/3 (1972) c 28.5 GeV/c W.H. Sims et al. (Ref. 49) d 69 GeV/c E. Pauli et al., Proc. oi the Aix-cn-Provencc Conf. 1973. p. Ci-360 e 102 GeV/c P..'Slattery, Univ. of Rochester Report, UR 432, COO-30G5-44 (1973) i 205 GeV/c Y. Cho et ai., Phys. Rev. Letters 31 (1973) 413 TAfiJ.E i. Comparison between Bubble Chambers and Counter-systems

1 Bubble Chambers (BC) Counters (C)

1. Vertex character As the BC is sensitive for charge tracks Simple countersystems are only sensitive in all directions it is easy to establish for particles in certain directions. The the character of the event concerning event type is thus less well established the charged tracks. Limitations are than for BC. In more advanced C-systems ; trongly clipping tracks relative to the all geometry is approached. positions of the cameras and very short stopping tracks.

2. Vertex position As the vertex is seen, it is possible to The vertex is reconstructed from the measure it's position well (of the order direction of detected tracks. For the main of 0.0!) mm in the chamber). Vertices bulk of configurations of tracks the posi- from suitably decaying neutrals (as A tion is less well determined than for BC and K°) are easily detected and measured (« 2 mm). The possibility to distinguish as well. between the tracks from a neutral particle decay near the vertex and the particles originating from the main vertex itself is more difficult than in a BC svstem.

3. Detection of neutrals There is low probability for direct ob- Special devices could be supplied con- servations of the effects of a neutral verting y's to e e~-pairs and detecting particle produced. The use of heavier these. nuclei as chamber liquid improves the detection probability for y but the "simpleneSs" of the hydrogen target in the reaction is then lost.

4. Charge track identification For individual tracks it is possible to The Cerenkov effect makes it possible to distinguish IT* from p up to » 1.5 GeV/c distinguish particles with different mass and K from T^up to 0.75 GeV/c using (e.g. K+ from p and 1T+ or K~ from JT" ionization judg tients. and p in limited angles).

5. Possibility to associate a set of Present day Bubble Chambers makes Simple counter systems have difficulties masses to the particles produced it possible to fit mass hypothesis for the to give overall fit's to mass hypothesis in an event (fit hypothesis) whole event up to medium energies for more complicated event topologies. (< 50 GeV/c) if £ 1 neutral particles are More complicated systems today manage produced in the event. events with up to 4 charged particles. 1 6. Beam particle type selection The BC needs a pure beam as it is not The C-systems have possibility to "label" possible within the sensitive time region subsequent^ incoming beam particles by for the BC to select between two subse- using e.g. a Cerenkov counter at the quently incoming beam particles of system entrance. different types. However, the use of a tagged beam improves the overall per- formance to some extent. As we use a proton beam without contamination this is not a problem.

7. Pre-selection of event types to The BC has no possibility to trigger for The C-systems have the advantage to be registered a special event type and use this trigger enable a preselection of event types to to inhibit the function for unwanted be recorded by the system. The spark event types. However, the flash is pos- chamber part of the system need not to sible to inhibit but this is generally be "fired" until a proper trigger re- considered not to be economical as the quires so. main cost is the accelerator and the expansion cost - not the flash - film cost. For rare event types this means that they are recorded together with more plentiful ones. Thus a tedious filtering must take place afterwards. For event types of relatively high production rate this is not a serious problem.

8. Intensity A BC cannot allow too many beam A C-system has a good time resolu- tracks per picture (i.e. accelerator tion between different subsequent beam burst) in order not to be too "crowded". particles entering the system. If the This is a limitation on statistics. accelerator burst is spread out in time this enables a larger number of events to be detected per burst than for a BC-system increasing the statistics.

Improvements of the two lines of techniques are continuously studied. The development moves towards different sorts of combined systems (hybrid systems) extracting the best features from both methods. Thus some of the bubble chambers which are planned for the future, incorporate among other things: (i) system for converting y's from 17°'s to e+e~-pairs inside the chamber (ii) external systems, to measure ionization of charged tracks (ii)more rapid cycling time's for the Bubble Chamber, increasing the number of sensitive periods per accelerator burst a factor of 10 as compared to earlier systems (1-2 per burst). TABLE 2. Bubble Chamber studies» of inclusive strange particle production in proton-proton reactions Number of Q ••• J s-2m Number accepted /"a Available CM-er.er&y Collaboration of PLAJ3 CM -energy CM-energy squared or pictures 2 K° (GeV/a) (GeV) (GeV) (GeV) Laboratory Main references Year *10-3 s

13 5.1 3.2 20.0 18 (5.0 4.1 SCO E.L. Berger et al. not Argonne-Michigan 1972 75 76S *> 21 6.4 4.5 41.0 Phys. Rev. Letters 2£ given 24 6.8 1.9 4(5.2 (1972) 322 28 7.4 5.5 54.8

12 4.93 3.0.i 24.3 Bonn-Hamburg- V. Blobel et al. Aix- 1973 Miinchen en-Provence Conf. 2539 ' 1661 2) H. Fesefeldt, thesis 1973 DESY Fl-73/11 Paper 11:1 1973 2389 2> 2 19 6.12 4.24 37.5 Scandinavian 2133 ' Paper 11:2 1974 182 30972) 2873 2) 2) Paper 11:4 1974 3609 - 21 2) 24 6.84 4.96 4)3.8 Bonn-Hamburg- - see 12 GeV above - 1973 1764 ' 1920 ' Miinchen

09 11.46 9.58 131.3 France-Soviet H. Blumenfeld et al, 2 1973 A 7fi ^ Union Aix-en-Provence Conf. i O

193.2 ri) 102 13.90 12.02 Michigan -Roches - W. Chapman et aJ. on 7R ^ ter UMBC 73-20, UR 457 1.1 I O i D

203 19.66 17.78 386.5 Argonne-NAL-Ames C. Charlton et al. A \ Michigan-Maryland Phys. Rev. Letters 30 1973 15 28 1^ 6re6 1' (1973) 574

.303 23.88 22.00 570.3 NAL-Univ. of Cali- F.T. Dao et ai. A •. fornia Phys. Rev. Letters 30 1973 35 20 * so1' (1973) 1151

Inclusive information can be extracted Irom the experiments at. 3.67 GeV/c (R.I. Loutttt ct a[., I'hys. Rev. _123 (1961) 1465) 5.4 and 6.S GeV/c (W.M. Dunwoodie, thesis 1968, University of California., report UCLA-1033) 8.0 OcV/c (M.W. Firebaugh, thesis 1966, University of Illinois and Phys. Rev. ^72. (1968) 1354) 24.5 GcV/o (J. Bartke et al«, Nuovo Cimentu 29 (1963) 8) 1) Back\vai-d c.rri. hemisphere. 2) Ambiguous A/Kg taken as A. TABLE 3a: Cross sections for strange particle pair product ir.r. :r. 1'• r«V/c (based cn V° measurements only)

Pair Inclusive Partical cross section } (ufc)

corrtsina^ion cross section i (Ub) 2-prong 4-prong 6-prong 8-pronT j 10-pronp

225 ± 2C 12C ± 15 90 :t 15 15 + n + 5 0 + 5

K°A 715 ± uc 335 ± 25 285 :t 25 80 + 15 15 + 15 , 0 + 5

+ K A 1060 ± 40 2 BO + 25 UP.5 i- 25 2G0 ± 15 30 ± 5 | 5+5

655 ± 25 140 ± 15 335 i 15 155 ± 10 2C ± 5 5 ± 5 ••s* I

TABLE 3b: Cross sections for A and K? single particle production.**)

Particle Inclusive Particle cross sections *) (yb)

type cross section i (pb) 2-prong 4-prong 6-prong B-prong 10-prong

A 1855+ 60 6M5+ 35 800 + 35 355 + 25 50 + 15 5+ 5

1270+ 40 HUO ± 25 580 + 25 215 + 15 30 + 10 5± 5

TABLE 3c: Cross sections for (K°E ) and (K°S~) pair production ; '.,. (both particles in the pair measured). Pair Inclusive combination cress section (ub)

KV . 200 + 100

•••' ^Z- ""• 100 + BQ

TABLE 3d: Gross sections for 2 , Z~ and s inclusive production.

Particle •....Inclusive type eioss section ;. i(tfb)-

;TOO + 200 -.250 + 100 : -30 ± ^20

. Misassigmnerit of prong nunber in priihary react ioii due to the presence of ; Dalitz'pairs andVor V°'s,decaying vvery close to the production point is esti- ; ; .. niated to be ,hegligible['l5]. 4

: ; ' iti/a pair.', contributions added. ; TABLE 4 Quantum numbers, mean charged multiplicity and average energy for strange particle parts and

their remiainder systems

Overall , Strange particle part of the event events Remainder system

Quantum numbers Quantum numbers Corres- CM energy Corres- Mean charged Mean CM Mean ponding for the ponding multiplicity energy charged Type type of remainder beam oom in the remain- GeV multipli- C B S C B S reaction system (GeV) (GeV/c) der system city

0 0 0 1.66 3.07+0.12 2 2 0 PP 4.;».6 8.7 3.07+0.12

K°A 0 1 0 2.50 3.37+0.13 2 1 0 TT+p 3.07 4.5 3.37+0.13

xx) + K+A 1 1 0 2.50 4.10+0.07 1 1 0 3.07 4.5 3.10+0.07

IT n A 0 1 — 1 1.67 3.81+0.06 2 1 +1 4.27 9.1 3.81+0.06

+ K P xJ Qt energy 6.1 GeV Charge (C) » + 2 Baryon number (B) = + 2 Strangeness (S) = 0

value for K°A is used LIST OF FIGURES

Fig. 1 The total, the inelastic and the elastic cross sections to pp-reactions as a function of p

Fig. 2 The main steps in the experimental processing of data.

Fig. 3 Prong number distribution for inelastic pp-reactions at 19 GeV/c Fig. 4 The invariant cross section

d ... 1 1 JE g , dpT2 versus x = PJ/PO for T~ K ° and A. oT Po dxdpT2 Fig. 5 The normalized transverse momentum cross section

7" ••E -i%2 • dpLversus 4for T" K°s T L T . ' Fig. 6 The normalized invariant cross section ——*—1 d—a

CT' . ?. • - ''

as a function of the cm. rapidity y for ir" K and A

Fig. 7 Test of factorization for the reactions pp -* Ax and K ps -» AX Tlie figure shows the ratio of the normalised inclusive cross sections for the two reactions at different t values. \, ,

Fig. 8a The on-line system and its connection to the CDC 8090-system.

ll ; • •••' .'•••. :•••• •:•••.• • -,•<:.'•: ..•;.• v.-.r . • .•." .••••;•:. '.•;'.,.• :::' ' . .' Fig. 8b The console on the measuring-machino. . .., v.

Fig. 9 The total strange particle production in proton-proton reactions as-

a function of the incident beam momentum. : ..:....• '

•• •••••' Fig, 10 Inclusive cross sections as a function of. incident momentum in pp-reactions for A and K^-i ... Fig. 11 Inclusive TT production cross section as a function of incident momentum.

Fig. 12 Semi Inclusive production cross sections as a function of incident momentum for KK, YK production in pp and irp-reactions.

Fig. 13 Comparison for AK and rfc semi inclusive cross sections between the results obtained in ref. [30] , our data and other world data.

Fig. 14 Average multiplicity of charged particles versus 8 (the cm. energy squared).

Fig. 15 Average multiplicity as a function of incident momentum in pp-reactions

for (n^o), (aK°) and -'

Fig. 16 The variation of the average multiplicity ( n ) on the number of negative particles produced (n ) for different beam momenta (given for v , K and A).

Fig. 17 The dependence on beam momentum for the slope a in the relation ( n ) = a n + 0 for the particles x = ir , K and A . x — o

Fig. 18 The average charged multiplicity in proton-proton reactions as a function of incident momentum.

Fig. 19 The dispersion versus the average charged multiplicity for inelastic pp-reactions.

Fig. 2C The dispersion versus the mean charged multiplicity for

a) events in which a A or a Ka is detected respectively o b) events in which a (K°K°) , a(K°A) or a(K A)-pair is produced.

Fig. 21 The mean charged multiplicity (n > for the remainder system (our rosulte) compared to the (n , > distribution as a function of incident mc^ient1 jr. for ch reactions with corresponding quantum numbers. Fig. 22a The correlation moment f plotted versus the available cm. energy Q.

Fig. 22b The t* moment plotted versus Q for pp-reactions in which a A or a K° has been detected. o

Fig, 23 The distribution of cross sections for various prong classes as a function of incident momentum, (Proton-proton reactions). a) overall inelastic pp-sample b) sample in which a K or a K has been produced (K „ observed) b c) sample in which a A has been produced

Fig. 24a Plot of

Fig. 24b Plot of (n)(cr /a. ,) versus (n/(n>) for the reaction pp -• n charged particles at incident momenta of 19 and 28.5 GeV/c.

Fig. 25 The modified KNO-distribution ¥('z') as a fuusttort of zF for events in which a A is detected, a K is det acted, a (K K ) pair, a fc> C=+1

(K A) pair or : ( K A) pair is produced.

Fig. 26 The Lorentz invariant normalized c. m. rapidity distribution for-inclusive O ""'"' ''> production in pp-reactions of if and K . ~ .„,, , /,-; Fig. 27 The Lorehtz invariant normalized rapidite y distribution in the laboratory system for inclusive production in pp-reactions of :

; a) TT b) K° •••"•' ' " . o) K . "' •• ; 1 1 I II t U | 1 1 I I I 111) 1 r~TTTTTTj 50 h PROTON-PROTON INTERACTIONS

0 ! 10 100 1000 INCIDENT LAB, MOMENTUM , GeV/c

Fig. 1 The total, the inelastic and the elastic cross sections in pp-reactions as a function of p . [313. EXPOSURE AT CERN

2m HYDROGEN BUBBLE CHAMBER

SCAN

> < V MEASUREMENTS ENETRA ENETRA SPIRAL ON LINE READER

CDC 3600 DATA PROCESSING DATA (REAF* FILTERING (POOH) SORTING GEOMETRICAL RECONSTRUCTION (THRESH) HYPOTHESIS FITTING (GRIND) DECISION (SLICE) STATISTICS (SUMX)

\ r V ANALYSIS

Fig, 2 The main steps in the.experimental processing of data. ioo f-

Fig. 3 Prong number distribution for inelastic pp-ractions at 19 GeV/c. ±

d(T 2 Fitbr 4 The invariant cross section distribution -1 JL f E 2 dpTl versus x = PL/p0 '

,c-

3 1 v- * JJf If Iv k>3 i o - a •I s •§ H

I I

Fig. 5 • Normalized transverse momentum cross section — f E °, dpT versus CT

b) C) _

Formula in text 0.305 - -febi ) -\6

10- I iV

D,t 1.2 i.a i.a 1.2 2.0 1.2 2.0 yCMS(K-.) yCM5(A)

Tig. 6 The nomaiized invariant cross section J_ ^ as a function of the c. m. rapidity y (from Or dy paper 11:1) a) tr b) K° c) A H. S curves are from thermq'dynamical model calculations i i 1 1

K*p data unfolded 2 - a

-4—

1

i

1

i 1 1 1 2 3 4 |t|(G«V/c)2 |t|(GeV/c): Fig. 7 Test of factorisation for the reactions pp Ax and K p -» Ax The figure shows the ratio of the normalized inclusive cross sections for the two reactions at different t values. The pp data are weighted by the factor F = •£( a (K p)/a. ..(pp)). TOE tot a) K p -* Ax data unfolded about x = 0.0 b) K+p -» Ax data folded about x= 0.0 Enetra

measuring

List device

Data Demand Signal Label Counting box buttons lamps display unit

Interface

Card Paper tape reader CDC reader

Line 0090 Paper tape printer punch

Magnetic Control Trans- Data tape mission unit unit Control:\

CDC 3600

Fig. 6a The on-line system and its connection to the CDC 8090 -

.system.- ...... • . ••• •. ...-,•-•. •.'•:• ;••.'• ...:,;•• >lntorface

1. "Enable" D 2. Erase last event" a 3. Erase last view" t 4. Erase last label a 5. "Erase last coordinate" b 6. Mot measurable" o 7. Now label" x 8- Change of label, left character" 9. CMnge of label, right character" 10. End of view" 11. "End of track" 12. .Read coordinate" 13. "New event"

Fig. 8b The console on the measuring-machine. Total strange particle production in proton-proton reactions 5 •

•S1 A I A

3 •

2 i l

1 m ' " ' ...... ,- . . .

lit | 10 15 2D 25 30 Ptab[GeV/cj

Fig, 9 The total strange particle production in proton-protpn reac- y H tions as a function of the incident beam momentum (from > paper II: 1 where references are given to the included ex- periments). . ;••

..••;

• 'I.1. " .a z 100 XXX) o o • i i 11 iy LU ' ' '"I K*/K* inclusive if) in o 10 ii

01 till 10 100 1000

INCIDENT BEAM MOMENTUM (GeV/c)

Kii{. HI inclusive cross sections us a function of Inci- dent momentum .it pp .A ' anything h) pp . K° or k° ' anything (Oat* fru.n references 1st Table Z). ^u 150 • If

7T»o inclusiv. e production in proton- prptphf react ion

.P. Id I

1sb I

; ' - . •" ""'• '•• • •/ . I 1111 1 1 t B

•,::»• 100 tooo v IpCIDENT BEAM MOMENTUM (GeWc) Fig. 11 ••• IiiclusiviB ir° p|e4Kic*it?R.C.ttJf!8;8e||3ttprn as a fanctipn of incident momentum p f LAB . . Gompllation 61'idata given in Ref. [39] . £

5 if)

tn o on u

10 20 30 40 3 )0 20 30 40 INCIDENT MOMENTUM (GeV/c) INCIDENT MOMENTUM (GeV/c)

Fig. 12 Semi inclusive production cross sections as a function of incident momentum for the relictions a) pp — KK * anvthine ij. 2 bi pp -KY + anything from paper 10.STRANGE PARTICLE PRODUCTION P* P»N5.

CTTOTAL °"KK

* °"RK

""TOTAL

0001 -I' '•.!•!• I' ' \ t 5 .10 20 50 LAB. MOMENTUM OF PiON, 6«V/c

Fig. 12 Semi inclusive production cross sections as a function of incident momentum for the. ro&ctions . • c) rrp -.KZ + anything i : f

Tip ~ KY -i- anything - pp-»AK ^anything 2.5 a)

« world data OUR EXPERIMENT E 2.0 o Berger-Smith Oh • i o 1.5 t~ o uu CO 1.0 CO CO o ce 0.5 o 0. 10 15 20 25 (GeV/c) PLAB

pp—»KK +anything b) 2.5 • world data a Berger-Smith Oh \ E 2.0

1.5 i o UJ CO i CO 1.0 t/> o a: i \OUR EXPERIMENT o 0.5

0. i 15 20 25 30 Fig. 13 Semi inclusive production croBS section as a function of incident momentum PJ_Ag for a) pp -AK ^ anything b) pp -KK i anything Comparison of world data (references in paper 11:2) and data from Ref. [30]. 10'

•0 a-' » "^" •

B- B~ B B •if— ^ "*• ^J -^ S10° r A 1 III ) 6 ? n • 3-a < p> Xio"1 — 1 "3 / S I t - / / a 1 2 1 Kf — • 1 - , 0 6

: /

/ A - • a • 4

i 11 iii i III 1 1 III t 1 1 1 1 M I i i i ( iin! i 10 »• rf . . .* s['Gev;2]

Fig. 14 Average multiplicity of charged particles versus s:. . (the o.m. energj'squared). Compilation ffivei; in Ref. f-jd"? 1 1 (GeV?c) Ref. I I a) 12 1.181 0.08 39 a (v) i 12 4 1.07t 0.12 39 b i 19 1.4 t 0.1 39c

1.0 \ 23 1.42 39 d

24 1.75*0.1 39 e

102 2.59*0.26 39f

1 205 3.17*0.32 39 g I b) 303 3.35±0.38 39 h I I 1100 4.7 39 i 0.1

, Plnb H ( (GeV/c) K s 12 0.0192*0.0005

19 0.042 ± 0.004 • 24 0.041 ± 0.001

69 0.13 ±0.02

0.0 • 102 0.14 ±0.02

205 0.20 + 0.03 • • 10 100 1000 303 0.3! ± 0.04

•T • • • 1 c) (GeVc) 0.1 I I I I 12 0.03"S'0.001 1 • 19 O.O6220.C03 1 24 0.05610X02 I • 69 0.114*0.016

102 0.0S84 0.002

205 0.Q 98*0.019

O.Ci - - 303 0.12710.03 * For references see Tab1- 2 .... 1 i 111 10 100 1000 PLAB(GeV/c)

Fig. 1: Average multiplicity as a function of incident momentum in pp-reactions for aKn^o;- Data from Ref. [39] b> - Data from experiments lifted in Table 2 . > D(=-O.O03tO.O06

proton-proton reactions

Thomas "-la'predicts nfno|n } /K[n..o| n ] »»d«pendent '• " 'eh' l Ivgl. ch1 of n from a one dimcnftional p:iis mndol. ko i t o s so n_

L"iR. in The average multiplicity

0.4

0.2

0

-0.2 t H 1 1—+-+ b) 0.05

0.03

0.01

-0.01 -i—i—i i i i 1—i—i

0.01

0

-0.01

-0.02

-0.03 20 100 Beam momentum (GeV/c)

Fig. 17 The dependence on beam momentum for the slope a in the relation

= an_ + P for the particles

a) x - TT'o Data from [39] b) x •- K°

O x -- A Data from experiments listed in Table 2 AVERAGE CHARGED. MULTIPLICITY IN pp REACTION 11 TTT 1—-i—i i Tin 1 1 1 -i i i i 111 —~i—T—i t i i ni— r—r V 15

0.323 1.23 s

2.04-ins-4.33

o • ARG.-B'HAVEN-CERN DC -& SERPUKHOV < ANAL • ISR • COSMIC RAYS

i i . i i I il 10 100 1000 10000 cm. ENERGY SQUARED, s, GeV

i i • i . • i • 11 10 100 !000 iOQOO INCIDENT LAB. MOMENTUM, GeV/c Fig. 18 The average charged multiplicity in proton-proton reactions as a function of incident momentum. Diagram from Ref. [31 "]• Individual experiments are listed in Ref. pp INTERACTIONS

3 & 5 6 7 8

AVERAGE CHARGED MUIT1PLPTY

Fig. 19 The dispersion D = ( - ) verBus the ch ch average charged multiplicity for inelastic pp- ch reactions (from Wroblewski [44]) 2.5 OVERALL PP INELASTIC

2.0 z o if)a:

1.0

0.5

20 llie dispersion D = versus the mean for aj events in which a: A or a K5 is detected respectively C + h) events in which a (K°K°)fi , a

p p incident iincident incident (GeV/c) (GeV/c) (GeV/c)

Fig. 21 The mean charged multiplicity <-a > for the remainder system (our results) compared to -; Ch a the < o^> values as a function of incident momentum for reactions with corresponding quantum numbers (from paper 11:2) '. a) remainder system to (K°K°) compared to pp initial state i b) remainder system to K°A compared to 7r p initial state ' f c) remainder system to A compared to K"*p initial state 20

( n a i) 1 lctt d Fig. 22a The correlation moment l2 = C ch^ ch"' 7-"V oh/ * P « versus the available cm., .energy Q = [yJ-|M.+M )]. Here

nch deribtes the number of charged particles;in the final state

and Vs"is.thecm..energy. M. and Mg are the; masses of the incident particles. /Data are shown for the.Indicated choices of particle k(iC, KT, andp); in all cases B = proton. This figure is taken from Ref,. [21 "J. A A inciutte X K* indusiv*

10

our experiment

10 20

Q (GeV)

Fig. 22b The f2 moment plotted versus Q for pp-reactions in which a A or a K° has been detected. o (Our calculation based on data from references given in Table 2) ) I J I NON-SP NON-SP NON-SP NON-SP 2-prong 4-prong 6-prong 8-prong

10 - I a) I II } s - - 5

n ..1 , t < ...1 , | , . I . I •00 300 300 10 100 300 10 WO 300

2-prong 4-prrng 6-prong 8-prong

~ b) z o II o ai l C/) , l IT) O ill O ioo KO 3CO 100 300 UO 3C0

A 2- A 7- A A 2-prong 4-preng 6-prong S--prong

c) ill-

103 J'.O 3G3 ':a 3:0 no

INCIDENT BEAM MOMENTUM (OeV/c)

23 "The distribution 6t cross sections for various prong classes as a function of incident momentum, (proton-proton reactions) ' . a)- overall ir.cl&stic pp-sample . ' b) sample in which a K° of a K? hae been produced^ , o) sample .in. which a A.has been produced... . . '•'•:•..•"... (References are given in Table 2) 10.0 10.0 pp — n charged particles pp—n charged porlictes 50-303GeV/c 19, 28.5 GeV/c

a) b) 1.0 i.o-

• _£o_ -W'

0.1 - 0.1-

0.01- 0.01-

0.0 J> 0.001 1.0 2.0 3.0 1.0 2.0 3.0

Pig. 24a Plot of {an/a ) versus (n/) for the reaction pp -*n charged particles at incident momenta of 50, 69, 102, 205 and 303 GeV/c. References to individual data points are given in Ref. [19 ]. Fig. 24b Plot of (cr /o\ ) versus (n/) for the reaction pp -.n charged particles at inci- dent momenta of 19 (from paper 1:1) and 28. S GeV/e 0 12 3

A =0.0585 u = I ' tf partial. vs. z = B= 0.S59 Inelastic

Full drawn curves are Y

"Fig. 25 The modified KNO-distribution ^>'( z1) as a function of z' for events in which a) a A is detected b). a K° is detected o c) u (K°K°) pai r is produced Data from paper 11:2 d) a (KtfA) pair is produced y.i,•.-• -'. •••" • ... ..;e) a \K"rA) pair is produced Fig. 26a TheLorentzinvariantnormalizedc.m. rapidity (yc^) distribution for inclusive production in pp-reactions of ir~ . Data from Ref. [67 ]. b)

r\ 10 H i i II

303 I 1 iff2 jjll If.j I I i -I I /ox + +

Hi l.i j I I • I I 1 • i i i . i i iii J 1 -2.8 -2JO -12 0.4 04 12 2.0 2.0 yCMS(K%)

Fig. 26b The Lbrentz.Invariant normalized c. in. rapidity (y9^) distribution for inclusive production in pp-reactions of Kg.: Data.from experiments listed in Table 2. . ;• . ..•.'. 1 • i V ff a)

\ 1

10"' — f1*

/ III ! ± £ / - (T dy /a /i < i

2 This exp. 10" n "it fi--*l **

• • L solid tin. 28.5 GeV/: - • 102 GeV/: - 0 205GeV/: - T ' 1 •

-

LAB -Q8 -QA 0.A 0.S 12 1.6 V Fig. 27a The Lorentz invariant normalized rapidity distribution in the laboratory system for inclusive production in pp-reactions of ir~. Data from Ref. [67 ]. 1 1 1 10~3 b) -

* — «2 • • I92Q«^E

i

•»

«• 1 il 2 10~ *

B> «

B D • A / *• 3 _ / / •a b" ¥/ f / t

+/ _ 10- T I

> • • • »— J-i 11

B 1 ; • ' *• !;

m

...... i S i \ •i. •- .;•-I"-' -0.4 0 1.2 1.6

Fig. 27b. The Lorentz invariant normalized rapidity distribution "'.-;. in the laboratory system for inclusive production in pp- . reactions of Kg; Data from expsriment8 listed in Table 2.

4 0 0.4 0.8 1.2 1.6 2.0 2.4 (A) Fig. 27c The Lorentz invariant normalized rapidity distribution in the laboratory system (for inclusive production in pp- reactions of A, Data from experiments listed in Table 2. •^£;M

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