From an exposure of the Argonne National Laboratory 12-foot bubble chamber to a beam of 12.4-GeV/c protons we have obtained a 3649-event sample of the reaction pp→γ+anything, where we observe photon conversions into e+e− pairs in the liquid hydrogen. We find that the invariant cross section for this reaction does not separate in its x and P⊥ dependence at our energy. By setting upper bounds on the cross sections for inclusive η and Σ0 production, we show that π0 decay is the dominant source of photons and therefore measure the cross section for inclusive π0 production to be σ(π0)=(31.5±2.6) mb. Comparison with the inclusive π+ and π− cross sections at 12.0 GeV/c shows that the relation 2σ(π0)=σ(π+)+σ(π−) is well satisfied. We confirm earlier indications that the average number of π0's per inelastic pp interaction is approximately independent of the number of associated charged particles produced.
Axis error includes +- 8/8 contribution (THE CROSS SECTION FOR NON-PI0 GAMMA PRODUCTION IS LESS THAN 2.3 MB AND HAS BEEN NEGLECTED IN OBTAINING THE 31.5+-2.6 MB CROSS SECTION FOR THE INCLUSIVE PI0 PRODUCTION).
Experimental results on $\pi^0$ production in $K^+$p interactions at 8.2 GeV/$c$ incident momentum are presented. Average $\pi^0$ multiplicities for given prong numbers are evaluated. They are consistent both with the corresponding results for pp interactions at 12 GeV/$c$ chosen for comparison because they have the same average prong number) and with a model where total multiplicity distributions are calculated from the Czyżewski--Rybicki formula and the charge branching ratios from the statistical model. Some averages over the $\pi^0$ momentum distribution are also evaluated. In particular it is found that $\pi^0$-s produced in two prong interactions go predominantly forward.
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Data from p+p→p+X at 102, 205, and 405 GeV and from π−+p→p+X at 205 GeV exhibit an approximate scaling property in the charged-prong multiplicity distributions as a function of the missing mass for the range 5<~MX<~13 GeV.
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Inclusive and semi-inclusive ρ 0 production are studied in 205 GeV/ c pp interactions. The number of ρ 0 per inelastic event is 0.33 ± 0.06, so that (13 ± 2)% of the π − are products of ϱ 0 decay. The ρ 0 are found to be produced mainly near y = 0 and tend to have larger average transverse momentum than do pions.
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The inclusive cross section and the average multiplicity are evaluated for most of the charged ( π ± , p, K ± ) and neutral (γ, π 0 , K 0 , K 0 , Λ, Λ , n ) particles produced in 32 GeV/ c K − p interactions; corresponding results are obtained for each charged topology separately. New results are given for the total charged multiplicity cross sections. The average longitudinal momentum of neutrals is found to be roughly equal to that of charged particles. The π + and π − multiplicity distributions are reconstructed and compared to the π 0 and to the total charged multiplicity distributions.
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Axis error includes +- 30/30 contribution (SYSTEMATIC ERROR FOR K0 MULTIPLICITY, WHICH IS EVALUATED FROM 2 ASSUMPTIONS: ALL K0'S COME FROM THE FINAL STATES (N K 2AK PIONS) OR (LAMBDA/SIGMA K AK PIONS) AND CHARGE DISTRIBUTION IN THESE FINAL STATES OBEYS A STATISTICAL ISOSPIN MODEL OF F.CERULUS,NC 19, 528. ALSO ASSUMED THAT SIG(K+)=SIG(KO). VALUES OF SIG(XI-) AND RATIOS SIG(SIGMA+)/SIG(LAMBDA), SIG(SIGMA-)/SIG(LAMBDA) ARE TAKEN FROM 14.3 GEV EXPERIMENT LOUEDEC 76,NC 41A, 166, STATISTICAL ERRORS BEING DOUBLED. FOR ALL ANTIBARYONS ASSUMED THAT SIG(ANTIBARYON)/SIG(BARYON)=SIG(ANTILAMBDA)/SIG(LAMBDA) =0.046+-0.020. SLOW PROTONS WITH PLAB < 1.2 GEV/C ARE IDENTIFIED, AN ESTIMATE FOR FAST PROTON PRODUCTION IS TAKEN FROM FACCINI 77,NP B127, 109).
Axis error includes +- 30/30 contribution (SYSTEMATIC ERROR FOR K0 MULTIPLICITY, WHICH IS EVALUATED FROM 2 ASSUMPTIONS: ALL K0'S COME FROM THE FINAL STATES (N K 2AK PIONS) OR (LAMBDA/SIGMA K AK PIONS) AND CHARGE DISTRIBUTION IN THESE FINAL STATES OBEYS A STATISTICAL ISOSPIN MODEL OF F.CERULUS,NC 19, 528. ALSO ASSUMED THAT SIG(K+)=SIG(KO). VALUES OF SIG(XI-) AND RATIOS SIG(SIGMA+)/SIG(LAMBDA), SIG(SIGMA-)/SIG(LAMBDA) ARE TAKEN FROM 14.3 GEV EXPERIMENT LOUEDEC 76,NC 41A, 166, STATISTICAL ERRORS BEING DOUBLED. FOR ALL ANTIBARYONS ASSUMED THAT SIG(ANTIBARYON)/SIG(BARYON)=SIG(ANTILAMBDA)/SIG(LAMBDA) =0.046+-0.020. SLOW PROTONS WITH PLAB < 1.2 GEV/C ARE IDENTIFIED, AN ESTIMATE FOR FAST PROTON PRODUCTION IS TAKEN FROM FACCINI 77,NP B127, 109).
The Split Field Magnet facility at the CERN ISR has been used to measure inclusive resonance production in inelastic p-p collisions at a c.m. energy of 53 GeV. The mass spectrum of pairs of oppositely charged hadrons shows a strong correlation, which can be explained as a consequence of dominant vector meson production, accounting for more than 60% of all pions and kaons produced.
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We present the first direct measurements of charged-particle multiplicity distributions for pp collisions at ISR energies. The measurements are performed by means of a streamer chamber detector with large solid-angle coverage and excellent multitrack efficiency. Particle densities are observed to rise in the central region as s increases. The multiplicity distributions in this region deviate from a Poisson Law, thus giving evidence for correlations. These correlations are of the same type as those obtained from clustering of the collision products. The mean charged multiplicity over the full rapidity range increases faster than log s . Our data do not support an early onset of KNO multiplicity scaling.
Pseudorapidity distribution at 23.6 GeV.
Pseudorapidity distribution at 45.2 GeV.
Pseudorapidity distribution at 62.8 GeV.
We present results on inclusive Δ ++ (1236) production in 100 GeV/ c p p interactions. In the region | t | < 1 GeV 2 we find a cross section of 1.29 ± 0.15 mb. Comparisons with pp interactions at high energies show Δ ++ production in pp and p p interactions to be very similar. The decay angular distributions of the Δ ++ are consistent with production predominantly through pion-exchange and the properties of the system recoiling from the Δ ++ are similar to those of real π + p interactions. However, the p π + background is found to show qualitatively similar behaviour. In contrast to the indications of Δ ++ production through pion exchange we also find evidence that events proceeding through diffraction dissociation are more likely to contain Δ ++ than other events. We present results on the forward production of Δ ++ in association with Δ ++ and protons.
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Inclusive and semi-inclusive distributions of γ's and π 0 's in the reactions K + p → γ + X and K + p → π 0 + X at 32 GeV/ c are presented and discussed. When compared to the inclusive π − production, the π 0 cross section is found to be significantly higher in low | x | and p T regions. The data are compared with other experiments and quark fusion model predictions.
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ESTIMATED FROM GAMMA AND 2GAMMA SPECTRA.
We study the multiplicity distribution of charged particles produced in 28-GeV/c pd interactions in the BNL 80-inch deuterium bubble chamber. We find that (18.3 ± 2.9)% of the three- and more-prong pd events result from double scattering in deuterium, a fraction observed to be constant from 28-to-400-GeV/c incident momentum. We extract pn topological cross sections from the odd-prong pd data by correcting for the effects of spectator visibility, double scattering, and Glauber screening. We find the dispersion of 28-to-400-GeV/c pd multiplicity distributions to have the same linear dependence on the mean multiplicity as found for pp data, while the pn data exhibit a different dependence. Both the pd and pn multiplicity distributions at 28 GeV/c are observed to be inconsistent with Koba-Nielsen-Olesen scaling.
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