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Mesons Produced in Proton-Proton Collisions

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Mesons Produced in Proton-Proton Collisions Lawrence Berkeley National Laboratory Lawrence Berkeley National Laboratory Title MESONS PRODUCED IN PROTON-PROTON COLLISIONS Permalink https://escholarship.org/uc/item/31g798p2 Author Peterson, Vincent Z. Publication Date 1950-05-22 eScholarship.org Powered by the California Digital Library University of California UNIVERSITY OF CALIFORNIA TWO-WEEK LOAN COPY This is cn Library Circulating Copy which may be borrowed for two weeks. For a personal retention copy, call Tech. Info. Division, Ext. 5545 BERKELEY, CALIFORNIA - i$?k! UCRL 713 4%,: %+ *.' !"\ .:, Unclassified Distribution UNIVERSITY OF CALIFORNIA Radiation Laboratory MBSONS PRODUCED IN PROITON-PROTON COLLISIONS Vincent Peterson May 22, 1950 Berkeley, California UCRL 713 Unclassified Distribution No. of Copies Argome National Labor ato sy Amed Forces Special Weapons Project Atode, Energy Codssf on, Washington BattePPe Menorid Institue Bmsh Beryllium Company Brookhaven National Laboratory Bureau of Medicine and -Susgery Bureau of Ships Carbide & Carbon Chemicals Div,, Union Carbide & Carbon Corp, (K-25 Plant) Carbide & Carbon Chemi cals Div,, Union Carbide & Carbon Gorp, (Y-12 Plant) Chicago Operations Office Cleveland Area Office, AEC Columbia University (J, R, ~dng) Columbia University (G, Failla) Dow ChmicaJ. Company H, KO Fesguson Company Genera3 Electric, Richland Harehaw Chemical Corporation Id&o Opera%ions Office Iowa State College 8 Kansas Ci%y Operations Branch Kellex Coqsratfon 'Knolls Atomic Power Laboratory Los Alamos Scientific Laboratory MalHnckkodt Chdeaf Works Massachusetts Institute of Technology (4, Gaudin) Massachusetts Institute of TechnoIogy (A, R, ~aufmann) Mound Labora-tozy National Advisory Committee for Aeronautics National Bureau of Standards Naval Radiological Defense Laboratory New Bmswick Laboratory Nev York Operaeons Office North American Aviation, Inc, Oak Ridge %bf onal Laboratory Patent Branch (Washington) Rand Corpo~ation Sandia Laborab ay Santa Fe Operakions Office SyEvania Electric Pmducts, Inc, Technical Infomation Evision (oak R5dge) USAF, Air Surgeon (R, H, ~lount) USAF, Direotor of Armament (c. I, ~rome) USAF, Director of Plans and Operations (B, L. ~~~le~ate) USAF, Director. of Research and Development (7,W, Bruner, and R, J, Mas on) USkF, EgT5m Air Force Base (K, K, compton) UrnL 73.9 Tfnclassified Distribution No, of Copies USAF, Kl rtiand Air. Force Base (H. Go Mentgomery, Jr, ) P BSAF, MatweEl Air Force Base (F, No ~o~ers) 1 USAF, XEPA Off2ce 2 USAT, ?ff',oe of Atomic hergy (A, A, Fiokal, A. C, ~onnell~)2 USAF, O$Pu.tf Ai i- Foree Base (H, R, Sullivan, Jr,) 1 USAB, Wright-Patterscn Air Force Base (~odne~~udenberg) E LT, S, Army, Atomic Ehergy Branch (A, W, Betts) 1 U, S,, Army, Amy Fkeld Forces (q~mes err) P Yo S,, Amy, Ccmmanding General, Chemical C~rpsTechnical C-d (J, A, MoLaugh1b thP.1~Mrs, G, Ben jamin) 1 C, 9, Amy, Chief of Ordnance (A, R, De1 amp) 1 3, 6, Amy, Camanding Officer Tfatertown Arsenal (~arso~1 H, ~sitrick) 1 U, So Army, Director of Operations Research (~llis~ohnson) 1 2, So A-my, Office of Engineers (B, D, Jones 1 U, So A~my, OPiYce of %he Chief Signal Offices (CU.T%ESTo C1aybon thry George C, HW~) 1 U. So Amy, Office of thR Surgeon General (8, So stone) 1 U, So GeoE0g%ca.1Survey (T~Be ~o1a.n) 1 IJ, So Public HeKLth Service P Ik~vessityof Cali foarnia at LOS AngePes 1 Uai~a~eit~of California. Radiation Laboratory 5 U_rlkva:x5Q of Rochester 2 11-1,.,-. VOF. ,.. sT-by $- afla&ingfan 1 Wsste:~Reses- University 2 We&'% nghous e Xleatric Compary 4 Unl?, cE Rauheuter, Phydas 9eparhent (B, E. ~arshak) -1 Total 143 UCRL 793 Page I. INTRODUCTION A. Statement of problem B, Energy considerations in proton-proton collisions 6, Direct production vs. subtraction techniques A. General experimental method B. The liquid hydrogen target C. Photographic method of detection D, Use of auxiliary sorting magnet E, Beam integration 111. EXPERIIEWTAL RZSULTS A. Formula for differential cross-section B, Line source experiment; energy distribution at 30' C. Point source experiment; energy spectrum at 30' using sorting magnet D. Angular distribution of p-mesons IV. DISCUSSION OF RESULTS A, Interpretation of peaked spectrum B. Existence of deuterons C. Total cross-section D. Angular distribution of the p-mesons LIST OF ILLUSTRATIONS '1, Maximum kinetic energy of n+ as a function of laboratory angle, 2, Method of producing a pulsed beam of deflected high energy protons from the Berkeley 184-inch cyclotron. 3, Liquid hydrogen target with pumping system, 4 Cross-sectional view of liquid hydrogen target (beam direction), 5, Line source container for liquid hydrogen, F, Target in place, showing filling and venting system. 7, Method of detecti by photographic plates, 8, Geometry of point source experiment using sorting magnet, 9, Geometry of emulsion detector, I 10, Line source geometry, 11, Range distribution of mesons in line source run. 12, Crosa-section vs, meson energy at 30' (line source), 13. Position distribution of meson endings in photographic plates (magnet run). 14, Range distribution of mesons (point source run). 15. Cross-section vs, meson energy at 300 (point source), 16. Angular distribution of y'-mesons in n+-r+ decay. I, INTRODUCTION A, Statement of problem, The particular interest in studying mesons produced in collisions of high energy protons with free protons, as compared to protons bound in nuclei, stems from the definite knowledge of the relative motion of the colliding nucleons, Mesons produced by nucleon-nucleon collisions within complex nuclei may be formed while the struck nucleon is moving toward, perpendicular, or even away from the impinging nucleon, Irrterpns&ation of the energy spectrum of mesons produced in such collisions rhust take account of the lack of exact knowledge of the dynamics of the collision pracess, and therefore the ability of the experimental data to discriminate between variations in theoretical predictions is reduced, If, however, an assemblage of free nucleons is used as a target for nucleons of a known high energy, the energetics of the collision may be calculate with little uncertainty, The case of high energy protons on hydragen is nearly ideal, The hydrogen molecule provides two protons "freen as far as high energy nuclear interactions are concerned, Protons are also ideal bombarding nucleons since they are capable of acceleration to high energy with a very narrow energy spread, The ,availability of a well-collimated beam of 349 Hev protons from the Berkeley 184-inch cyclotron makes this experiment possible, Experiments concerning the production of mesons may be expected to indicate which features of present meson theories are qualitatively correct, and furnf sh quantitative checks with which any future meson theory must agree, It is always to be hoped that'the experimental results will contain striking features from which properties of the meson or meson-nucleon interaction ma'' be deduced directly without recourse to detailed calculations, The study of mesons produced from hydrogen is a logical culmination of the knowledge and techniques gained from earlier experiments on simpler targets. Gardner and ~attes'made the first estimate of the meson production from carbon, using the photographic plate technique with the internal circulating cyclotron beam, Later Peterson2 measured the differential cross-section for production of mesons from carbon in the forward direction at low meson energies for both 380 Mev alphas and 350 Mev protons inside the cyclotron, The external deflected proton beam was first used for meson production experiments by Richman and ~ilcox~and IVeissbluth4 to study mesons produced from carbon and lead, This method offers the advantages of a well-collimated beam and a field-free region to study angular and energy distributions over the full range of meson energies, These experiments measured the energy distribution of positive and negative mesons produced in nucleon-nucleon collisions within nuclei, The results provide the first extensive experimental check on meson production calculations, although their implications are somewhat obscured by the effects of internal nuclear motion, Production from free protons is an obvious experiment to provide a more severe test of the theory. ".". B, Energy considerations in proton-proton collisions, In order to produce a mass 276 n meson from a stationary proton, the incident proton must have at least 292 Mev of kinetic energy, This high threshold energy means that the mesons created by collisions of 340 Mev protons with hydrogen will have, in the proton-proton center-of-mass system, kinetic energies of 20 Mev or less, The motion of the center of mass system is given by a fi of 0,39, while the p of 1 E, Gardner and C,M,G, Lattes, Science, -102, 270 (19481, %, Z. Peterson, Pfiys, Rev, -75, 1469(~)(19481, 3~,Ri chrnan and H, A, WiPcox, UCRL-592, 4~.Veissbluth, Thesis, UCRL-568, a 20 hrev n meson is O,4B, Thus upon transformation to the laboratory system, we will expect to find that a large fraction of the mesons will emerge in a generally forward direction, Presumably the only two reactions leading to the formation of a positive A meson in proton-proton collisions are: 4- (a) p -t. p --P p -+ a .C n In case (a) the maximum value of the continuous distribution of possible meson energies can be readily calculated and represents a definite upper limit beyond which no mesons should be observed, In case (b), whose possible existence was first pointed out by arka as^, the collision process is a two-body problem and the mesons formed
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