Neutral-pion production in pp interactions has been studied using 8000 photon conversions in the Fermilab 15-ft bubble chamber. Inclusive π0 multiplicity moments and ππ correlation integrals are presented; f200 is determined to be + 3.0±0.8. For the semi-inclusive π0 multiplicity distributions we find 〈n(π0)〉n− to increase with n−, while the dispersions are n− independent. Results on f2−0, f200, and f2,n−00 are compared to predictions of simple cluster models.
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Inclusive and semi-inclusive cross sections for gp0 production in 100, 200, and 360 GeV/c π−p interactions are presented. Differential cross sections for ρ0 production as functions of c.m. rapidity and transverse momentum are compared with the corresponding differential cross sections for pion production. Effects of various methods of estimating background on the values obtained for ρ0 production cross sections are discussed. About 10% of the final-state charged pions appear to come from ρ0 decay. Thus, while ρ0 production and decay is a significant source of final-state pions, other sources must contribute the majority of the produced pions.
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We have studied inclusive KS0, Λ, and Λ¯ production and strange-resonance production in the reactions pp→(KS0, Λ, or Λ¯)+π±+anything at 405 GeV/c. The observed cross sections are 7.43 ± 0.45 mb for KS0, 4.01 ± 0.35 mb for Λ, and 0.63 ± 0.12 mb for Λ¯. From the analyses of the effective-mass distributions for the (KS0π±), (Λπ±), and (Λ¯π±) systems, the resonance production cross sections are determined as 4.1 ± 1.0 mb for K*+(890), 3.6 ± 1.0 mb for K*−(890), 3.4 ± 1.7 mb for K*±(1420), 0.67 ± 0.12 mb for Σ+(1385), 0.45 ± 0.09 mb for Σ−(1385), and 0.25 ± 0.08 mb for Σ¯±(1385). The inclusive total and differential cross sections are discussed in comparison with data at lower energies. The direct production cross sections for pseudoscalar, vector, and tensor K mesons are estimated to be 2.3 ± 1.2, 3.4 ± 1.0, and 1.7 ± 0.8 mb, respectively. Direct pseudoscalar-K-meson production accounts for less than one-third of the total inclusive kaon production. Evidence of vector-meson dominance in inclusive meson production at high energy is indicated.
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Charged-particle multiplicity distributions in 400-GeV/c pd interactions have been studied in an experiment in the Fermilab 30-inch bubble chamber. From the fractions of odd-prong and backward-proton events, a rescatter fraction of 0.22±0.01 is found (for N≥3). The pn multiplicity distribution is obtained from the odd-prong distribution plus a no-cascade assumption. After making one-prong and two-prong estimates, mean charged-particle multiplicities of 9.49±0.12 for pd (including slow particles) and 8.57±0.12 for pn are obtained. In the incident momentum range 100 to 400 GeV/c, pd and pp distributions are very similar to each other and are different from pn distributions.
Axis error includes +- 0.0/0.0 contribution (?////SHORT PROTON VISIBILITY, UNOBSERVED DALITZ PAIRS, UNOBSERVED VEES, UNOBSERVED CLOSE SECONDARIES, UNCOUNTABLE EVENTSTHE ONE- AND TWO-PRONG EVENTS WERE NOT MEASURED AND WERE ESTIMATED USING ADDITIONAL ASSUMPTIONS AND DATA OF OTHER EXPERIMENTS//TO OBTAIN THE FREE-NEUTRON DISTRIBUTIONS THE ASSUMPTION THAT RESCATTERING IS MULTIPLICITY INDEPENDENT HAS BEEN MADE, AND CORRECTION FOR DEUTERON-FINAL-STATE EVENTS AND FOR WAVE-FUNCTION SYMMETRY REQUIREMENTS HAS BEEN MADE).
Axis error includes +- 0.0/0.0 contribution (?////SHORT PROTON VISIBILITY, UNOBSERVED DALITZ PAIRS, UNOBSERVED VEES, UNOBSERVED CLOSE SECONDARIES, UNCOUNTABLE EVENTSTHE ONE- AND TWO-PRONG EVENTS WERE NOT MEASURED AND WERE ESTIMATED USING ADDITIONAL ASSUMPTIONS AND DATA OF OTHER EXPERIMENTS//TO OBTAIN THE FREE-NEUTRON DISTRIBUTIONS THE ASSUMPTION THAT RESCATTERING IS MULTIPLICITY INDEPENDENT HAS BEEN MADE, AND CORRECTION FOR DEUTERON-FINAL-STATE EVENTS AND FOR WAVE-FUNCTION SYMMETRY REQUIREMENTS HAS BEEN MADE).
Axis error includes +- 0.0/0.0 contribution (?////SHORT PROTON VISIBILITY, UNOBSERVED DALITZ PAIRS, UNOBSERVED VEES, UNOBSERVED CLOSE SECONDARIES, UNCOUNTABLE EVENTSTHE ONE- AND TWO-PRONG EVENTS WERE NOT MEASURED AND WERE ESTIMATED USING ADDITIONAL ASSUMPTIONS AND DATA OF OTHER EXPERIMENTS//TO OBTAIN THE FREE-NEUTRON DISTRIBUTIONS THE ASSUMPTION THAT RESCATTERING IS MULTIPLICITY INDEPENDENT HAS BEEN MADE, AND CORRECTION FOR DEUTERON-FINAL-STATE EVENTS AND FOR WAVE-FUNCTION SYMMETRY REQUIREMENTS HAS BEEN MADE).
Cross sections and charged multiplicity distributions forK+p interactions at 70 GeV/c are presented and compared withK+p data at other energies. Comparisons are also made with available π+p,pp, andK−p data.
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The cross section for the process e + e − → multihadrons has been measured at the highest PETRA energies. We measure R (the total cross section in units of the point-like e + e - → μ + μ - cross section) to be 2.9 ± 0.7, 4.0 ± 0.5, 4.6 ± 0.4 and 4.2 ± 0.6 at s of 22, 27.7, 30 and 31.6 GeV, respectively. The observed average multiplicity, together with existing low energy data, indicate a rapid increase in multiplicity with increasing energy.
STATISTICAL ERRORS ONLY. RADIATIVE CORRECTIONS APPLIED AND TAU HEAVY LEPTON CONTRIBUTION SUBTRACTED. AVERAGE VALUE OF R FOR ALL THESE DATA IS 4.14 +- 0.26.
AVERAGE CHARGE MULTIPLICITY. ADDITIONAL, SYSTEMATIC ERROR IS ABOUT 1.5.
Inclusive K0K¯0, Λ0, and Λ¯0 cross sections have been determined using a 292-event/mb exposure of the hydrogen-filled 15-foot bubble chamber at Fermilab. From the invariant-mass distributions of V0π± pairs we find that σ(K*±(890))=4.4±1.4 mb, σ(Σ*±(1385))=0.54±0.40 mb, and σ(Σ¯*±(1385))=0.45±0.34 mb. It is estimated that 0.32 ± 0.11 of K0K¯0's, 0.21 ± 0.16 of Λ's, and 0.96 ± 0.75 of Λ¯'s originate from decays of K*(890) and Σ*(1385), respectively.
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Inclusive charged pion production is studied in an exposure of BEBC, filled with hydrogen, to an incidentK+ beam of 70 GeV/c. Total cross sections for pion production and inclusive longitudinal and transverse momentum distributions of π−'s and of positive particles are presented and compared with data at lower energies. Earlier evidence for scaling in the fragmentation regions is confirmed. The central region π− cross section increases proportionally topLAB−1/4; positive particles show almost no energy dependence atx=0. Particle ratios π+/π− are studied as a function ofx andy* and a comparison with 70 GeV/cK−p data is made. Analysis of structure functions for (ππ) pairs and of particle production associated with π± triggers at large |x| in the context of quark/parton models, provides qualitative evidence for the diquark-quark structure of the proton.
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Results on inclusive K s 0 production in e + e − annihilation at mean center-of-mass energies of 9.4, 12.0 and 30 GeV are presented. The ratio R (K 0 ) = 2 σ (K s 0 )/ σ μμ rises from 3.10 ± 0.75 at √ s = 9.4 GeV to 5.6 ± 1.2 at √ s = 30 GeV, corresponding to an approximately constant K 0 /charged-particle ratio of 0.12 ± 0.02. A similar ratio for K 0 / charged particle is observed for direct hadronic decays of the ϒ.
SYSTEMATIC ERROR INCLUDED.
NUMBER OF K0 PER HADRONIC EVENT. AUTHORS ALSO USE MULTIPLICITY TO ESTIMATE NUMBER OF K0 PER CHARGED PARTICLE.
INCLUDING EARLIER DATA.
The Fermilab hybrid 30-in. bubble-chamber spectrometer was exposed to a tagged 147-GeV/c positive beam containing π+, K+, and p. A sample of 3003 K+p, 19410 pp, and 20745 π+p interactions is used to derive σn, 〈n〉, f2cc, and 〈nc〉D for each beam particle. These values are compared to values obtained at other, mostly lower, beam momenta. The overall dependence of 〈n〉 on Ea, the available center-of-mass energy, for these three reactions as well as π−p and pp interactions has been determined.
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