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Proceedings of the Topical Workshop on Forward Production of High-Mass Flavours Ii at Collider Energies

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Proceedings of the Topical Workshop on Forward Production of High-Mass Flavours Ii at Collider Energies L.RC.8013 PROCEEDINGS OF THE TOPICAL WORKSHOP ON FORWARD PRODUCTION OF HIGH-MASS FLAVOURS II AT COLLIDER ENERGIES HELD IN PARIS COLLEGE DE FRANCE November 28-30 1979 'J3° iCfcr9. QyM*Sl)k\f / H Edited by G. Fontaine Laboratoire de Physique Corpusculaire College de Frinct 11. PUce Marcelin Bcrthclot . F75S31 PARIS Cedex 05 PROCEEDINGS OF THE TOPICAL WORKSHOP ON FORWARD PRODUCTION OF HIGH-MASS FLAVOURS AT COLLIDER ENERGIES HELD IN PARIS COLLEGE DE FRANCE November 28-30 1979 I S 1 M G C 0 M H 1 T E E : FONTAINE, M. 'ROISSART, C. GHESQUIERE, J. PRENTKI, G. INTRODUCTION. Tin.- present volume contains the proceed! n^s of the "Topical Workshop on forward production of hifih-rr.ass flavours at collider energies" held in Paris, ('...lene do France, November JS-10, 1979. The aim of this workshop was to discuss all the aspects (both experimental and theoretical) of this new domain of Physics recently opened up by the obser­ vation ni" a penetrating component i n cosmic-ray i nternr i ions and of charmed ::I-S.MIS and baryons in the forward d i reel ion a I l he I.S.I;.. These rel" 1 exi uns weiv further motivated by the preparation of new ;>p colliding facilities of II'.IH b higher energy and where experiments conii :m soon could prof i t ably cover | this field of interest. This workshop gathered about 90 participants from 11 countries and gave them the opportunity to exchange information and opinions in a rather informal a trios pi: ere. It is a p ieasure to thank warxl y all of them for thei r cone ri but ion to Lhe success of this meeting, and specially the speakers and those who pré­ parée1 the workshop in specialised working groups. A particular mention has to be made of Dr. M.K. GALI.I.AK1) and R. PETRONE 10 who have led a fruitful round taille discussion on theoretical aspects, which unfortunately could not be reported i n these proceed i nus. All papers included in the present publicat inn have been reproduced as rhey were prepared by the authors. They are divided into three subjects : - experimental results - Theoretical aspects - New experiments. The orjvï:iÎ5ins commî(Coe also wishes to acknowledge the precious help ^i all those who have directly or indirectly contributed to the preparation of cne workshop and of these proceedings : M. KELLER, (C.E.R.N.); M.S. DETOEUF and M.F. CHICANNE, (I.N2.P3.), C. BREON, E. BROCHET, G. MASSEl, Y. RUELLE, Y. GIRAUU-HERAUD, T). KRYN, G. ARBOUSSE-BASTIDE, X. LE TAN and J. ORILLON, (Collège de France). G. FONTAINE 1 A/ KXl'KKIMKNÏAL RKSl'LTS. Forward Production ol low m.iss flavours at Liu- C.K.R.N. I.S.R. V. Ci: I ST Kxper iment.i I ri'V i ew of charm hadroproduct ion y. Mn.i.HK Comments mi 1 prnilucl i nn at the T . S.R. B5 Kq K. SOSNOU'SKI St rue Lure of I1 rnL on-Pro tun sions with a c harried hadron pr.uîureti. A. iHAMANT-Br.RCKK Study of the forward production of ti i^h-mnss .systems .-H the I.S.R. 99 ^1 I>. CLINK High energy particLe interactions from 10-1000 TiiV"': Cosmic ray data and Proton- (Awtrff Proton col l.ûJ-c'rs". 109 V . ML'RAKI Cosni c my s and new ace el crator experiments. l2tJ qa i!/ THKORI-TICAI. ASPECTS. II. FRITZSCH B particles. i43 q^, C. PKTKKSON TheDrelica] Predictions for hifih-mass flavour production in Hadron-Hadron collisions. 155 q 4 P. KKSSLLCR YY versus Drell Yan effect in pp or pp •storage rin^s. 187 4 ST (7 NEW EXPERIMENTS. in pp interactions at 540 GeV .n energy 195 <j€ W.G. SCOTT Particle identification using dE/dx 209 ^ F. C'.ERADINI fl flavour production in the forward aria of the UA1 experiment. 229 Cff Muon detection and background from normal events for a possible forward muon detector. 257 <3>^> C. GHESQUIERE Study of a muon forward trigger in UAI experiment. 280 | &0 C. KUBBIA Instrumentation developments and potential impact on collider detectors. 297 |0| pp collider at Fermi]ab. 3°9 | Oil LIST OF PARTICIPANTS. ( rOKU'ASD PRODUCTION OF LOW MASS FLAVOURS AT THE CKRN/ISR J.C. Sens 1. INTRODUCTION The purpose of this cent ri but ion is three* fa Id : 1) To .show that in a subset of al l-hadro:iic processes, i.e. the ones in wiii ch a large fraction ol Lhe incident energy is transferred to one single secundary the dominant mechanism may hi- ^lunn exchange. 2) To show that gluon exchange provides a natural explanation for the [acL that baryons (n, :'i, .'. ) rosp. mesons (-, K) are produced with distributions in momentum which decrease slowly, rcsp. rapidly with increasing momentum. 3) To provide a recipe for calculating the distribution in x and p of t\ and \, states which D the SPS pp collider. The data on which the conclusions are based have been obtained witli single and double arm spectrometers placed at very small angle with res­ pect to the primary beams at the CERN/ISR. Fig. I shows the old, con­ servatively designed spectrometer dating back to 1970 of exp. R201 ; Fig. 2 shows the stream lined spectrometer operational since 1978 of R607. Typical solid angles are 10 - 10 sr, typical, momentum resolution -£ *= 0.5 - 1 % at 25 - 30 GeV. A typical particle spectrum obtained in 2 minutes ISR time is shown in fig. 3, positives on the ri^ht, negatives on the left. The main features are apparent at once: A rapidly falling specirum of negatives, essentially n , and, at the positive side, an InviLed talk at the workshop on the production of high mass flavours, Paris, November I960. Present address: S1.AC, P.O. Box 4349, Stanford CA 94305 U.S.A. assymetric peak, corresponding to ;lastically and quasi-elastically scattered protons, and at lower momenta a spectrum which is (after subtracting the IT spectrum {=* s pec" rum) from it) flat and consists mostly of protons. Fig. 4, 5 show samples of production spectra obtained with 2. 7T /TT = 2 -* 5 for x = 0.5 - 0.9 3. K+/K~ > 50 for x ? 0.7 U. o(K ) > affr ) for x > 0.7: crossover 5. Perfect scaling (fig. 5) II. GLOBAL COMPARISON pp - MESON/ep -<• eX Assuming a fast v to consist of a valence u quark from the proton, coupled to a slow d quark from the sea we may expect, in first instance, the following relations between the x dependence of the inclusive cross section for ^ , K , " production and the momentum distribution u(x) and d(x): <-.T(/Tr,;t) * T(/C>) xufx.) Vie can then relate the production of fast pions to deep-inelastic lep- ton scattering by noting that for high x, to a good approximation: x ' ? ' '/ Corcp;it i us t ïic (J(.N) ;ind d f .\) from deep-i ne List i c data we obtain l lu1 ivsiil Ls of £ i gs. 6, 7, 8, whuru the 1 ir.es are the computed u(x) and d(>:}, aparC frofl îr.e p-dependent normal iz.it ion constant per particle tvpe. The agreement is good up to x * 0.7( for x • 0.7 there are large tU-vi at ions, as ill us traced also in fig. 9 where various rat j ns are cotn- p.uvd i.i th the computed ration of the quark di st r i butions. V.'c shal 1 sec in-1 ow that these discrepancies can be complete ly removed in a more de~ t.ii l^-c rcodei . III. COL'NTK.'G RULES, OLD AN'D NI-;',; Counting rules are based on :;-ie notion of equiparriLion of energy giver. of f ts tiif proLon by the ether protsr. in the ac:_ of an ini e race ion producing a final state particle. We can classify this process by noting that in an interaction we have an exchange and that we have a number of spectators, who, as spectators do, share in the exci teraent while watching the parade. We have 3 types of exchange: exchange of gluons (g) , valence quarks (qt ) or ^ea quarks (c . ). And there arc two ways of sharing the energy: 1) it gets shared among al1 (valence and sea) quarks standing by while the produced particle leaves the proton (/The Brodsky-Gunion Counting rule") or 2) it gets shared among the valence quarks only ("The valence counting rule"). There is of course the third possib) '. : *-y of sharing among sea quarks only but sea quarks are known (from pp -* -,. ->voerinencs e.g.) to have very small average momenta and steeply falling sea distributions, so chey do not enter into this picture of high x mesonproduction. So with 3 exchanges and 2 ways oî counting the spectators we have 6 possible cases. How do we know whicii is which? The ans'-'er is we don't for sure buL we can try and make the plausible ;is.-un'.pLi'on that the Larger the number of spectators .\' the lower the energy K'f!: for the - will be on average. Thus the rnonenturr: spectrin of titu ~ ::IUSL decrease faster with increasing x, the larger the nuT.bri: ,\". Brod.sky .znd Cimion liave shown from field theory arguments that for N spectators the dependence on x is given by (/-*-)" * = *#-/ & For example tiie inclusive production of ~ mesons of high x and srcalî _ ) ) - n = 2 n=2 n = 1 v v v n = ] n = 0 n » I s s s n=3 n=2 n =2 where n , n is the number of valence and sea spectators and n = n + n • V S ^ V S From eq.
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