Charged Pion Multiplicity Research Articles

Comparison of models for neutral and charged pion multiplicities observed in 25 GeV/c π−p collisions

Cross sections have been obtained for events having a topology of 0 to 16 charged tracks and no strange particles in 25 GeV/ c π − p interactions. The average number of neutral pions, n π o , for each topology was determined from a study of e +e − pairs converting in the hydrogen and in a Ta plate. Topological cross sections agree rather well with the multiperipheral model of Chew and Pignotti, with the conjecture of Wang on local production of pion pairs, or with a Poisson distribution of produced pions coupled with isospin independence. The latter model also sucessfully describes the number of charged tracks occuring with Λ o K o and K o K o . However, these models do not reproduce the measured value of n π o.

Proton-proton collisions at 3.5 GeV

Ilford G-5 emulsions were exposed to an external, 3.5 GeY proton beam of the Berkeley Bevatron. A total of 1200 nuclear interactions of beam protons was located, of which 128 were identified as protonproton collisions. Multiple scattering, blob density, range and angle measurements were employed to determine the cross-sections for elastic and inelastic interactions as well as the identities and center-of-mass system momenta and scattering angles of secondaries from inelastic proton-proton interactions. This analysis indicates a cross-section of (8.0±2.4) mb for elastic events, (24.1±2.9) mb for two-prong inelasitc events, (7.9±1.4)mb for four-prong events and (0.6±0.3) mb for sixprong events. The mean charged pion multiplicity in inelastic interactions is 1.5±0.2 and corresponds to an average degree of inelasticity of 0.45 ±0.06. Center-of-mass system angular distributions of charged secondaries from inelastic events display a peaking for small scattering angles which is most pronounced for protons and pions from events with low secondary multiplicity. Momentum and transverse momentum distributions of secondary protons and pions from inelastic events are presented and compared with the results at other energies. The angular distribution of elastically scattered protons is found to be in fair agreement with that predicted by a uniform optical model of radius 1.25-10-13 cm and opacity 0.66.

Some characteristics of inelastic proton-nucleon collisions produced by protons of energy 6.2 GeV in nuclear emulsions

Nuclear interactions produced by protons of energy 6.2 GeV in nuclear emulsions have been analysed to deduce information regarding some of the characteristics of proton-nucleon collisions. 703 disintegrations have been obtained by « along the track » scanning. Accurate measurements of multiple scattering and of grain density have been made on favourable tracks of relativistic secondary particles; using these measurements it has been possible to identify the particles up to the highest energies involved. It is found from this investigation that in collisions of protons of energy 6.2 GeV with nucleons:a) the mean charged pion multiplicity is 1.51±0.18;b) the mean inelasticity is 0.43, and is, within errors, independent of the total multiplicityns;c) the nucleons recoiling in the C.M. system are very strongly collimated symmetrically in the forward and backward directions;d) the mesons created in the collision also show an appreciable amount of forward-backward collimation in the C.M. system.

Inelastic Proton-Proton Collisions at 6.2 Bev

Inelastic, 6.2-Bev proton-proton collisions in nuclear emulsions are examined using the internal beam of the Berkeley Bevatron. Multiple scattering, grain density, range, and angle measurements yield the momentum spectra and angular distributions of secondary pions and protons together with the cross sections for accessible final states. The results indicate a cross section of 7.3\ifmmode\pm\else\textpm\fi{}4.6 mb for two prong events, 12.1\ifmmode\pm\else\textpm\fi{}2.4 mb for four prong events, 2.7\ifmmode\pm\else\textpm\fi{}0.6 mb for six prong events, 0.3\ifmmode\pm\else\textpm\fi{}0.3 mb for eight prong events, and 0.2\ifmmode\pm\else\textpm\fi{}0.2 mb for ten prong events, giving a total inelastic cross section of 22.6\ifmmode\pm\else\textpm\fi{}5.3 mb. The average charged pion multiplicity was found to be 1.9\ifmmode\pm\else\textpm\fi{}0.3 and the value of $K$, the average degree of inelasticity, 0.49\ifmmode\pm\else\textpm\fi{}0.05. Comparison of observed partial inelastic cross sections with the predictions of the Fermi statistical theory indicates that this theory underestimates the relative probability for states with high meson multiplicity. Considerable forward and backward peaking was observed in the center-of-mass system angular distributions for secondary protons and, to a lesser extent, for secondary charged pions. Center-of-mass system momentum distributions for secondary charged pions peak at lower momenta than predicted by the statistical theory, while those for protons peak somewhat higher than predicted. Effects are discussed which could account for these discrepancies.