Data on muon-pair production by pions are used to determine the momentum distribution for valence quarks in the pion. The shape of a nucleon structure function is also obtained and is compared with a calculation based on existing data.
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Momentum spectra for forward Σ− production on beryllium by protons of momentum 25.8 and 29.4 GeVc are presented. Data for the two primary proton momenta are compared for scaling behavior in the invariant cross section. In addition, the observed single-particle momentum distributions are compared with single-particle spectra from other inclusive reactions initiated by protons.
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Photoproduction of $\Lambda$(1520) with liquid hydrogen and deuterium targets was examined at photon energies below 2.4 GeV in the SPring-8/LEPS experiment. For the first time, the differential cross sections were measured at low energies and with a deuterium target. A large asymmetry of the production cross sections from protons and neutrons was observed at backward K$^{+/0}$ angles. This suggests the importance of the contact term, which coexists with t-channel K exchange under gauge invariance. This interpretation was compatible with the differential cross sections, decay asymmetry, and photon beam asymmetry measured in the production from protons at forward K$^+$ angles.
The measured differential cross sections from the liquid hydrogen target, protons, as a function the K+ polar angle.
The measured differential cross sections from the liquid hydrogen target, protons, as a function the photon energy at forward K+ polar angles of 19-43 degrees .
The measured of differential cross section at backward K+/K0 polar angles of 120-150 degrees as a function of photon energy from the liquid hydrogen target, protons, and liquid deuterium target, deuterons.
Results are presented on a series of measurements of ρ-photoproduction from hydrogen, deuterium, and complex nuclei ranging up to lead, at photon energies ranging from 4 to 9 GeV. Detailed dipion mass-spectrum fits are presented, using a Drell-type nonresonant background and its interference with the resonant amplitude, with no other arbitrary backgrounds. For hydrogen and deuterium, the inelastic contributions have been subtracted. The A dependence of the cross sections is analyzed to yield values of γρ24π and σρN at average photon energies of 6.1, 6.5, and 8.8 GeV. The hydrogen-to-deuterium ratios indicate the presence of possible nondiffractive amplitudes at low energies which then decrease with energy.
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We present the results of a study of muon pairs with invariant masses greater than 4.05 GeV/c2 produced in high-energy pion-nucleon interactions. The production cross section together with the inferred pion and nucleon structure functions are reported and compared with other experiments and with QCD predictions. The transverse-momentum distributions are also presented. Finally, the full angular distribution in cosθ and φ is given as a function of mass, Feynman x, and transverse momentum. Longitudinal photon polarization is seen in the lower portion of the mass range at high xπ. This result is compared with a higher-twist model.
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Observation of 16 μ + μ − pairs of invariant mass greater than 2.7 GeV/ c 2 in the reaction pp → μ + μ − + anything at s = 52 GeV at the CERN Intersecting Storage Rings (ISR) is reported. These events can be interpreted as originating from J(3.1) decay into μ + μ − . Their p T distribution suggests a hadronic production. The cross section for J production is given and compared to the cross section for single lepton production. We conclude that J(3.1) production cannot fully account for single lepton production.
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We present data on inclusive and semi-inclusive ϱ 0 production in 147 GeV/ c π − p interactions. We find a total cross section of 7.3 ± 1.3 mb. Most of this cross section is found in the lower topology events (⩽ 10 prongs), and in the central and forward rapidity regions. The P T 2 dependence of ϱ 0 production, 〈: n > ϱ 0 per event, and the ϱ 0 / π + ratios are also discussed.
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Data, obtained from p-p collisions at centre-of-mass energies between 31 and 63 GeV, are presented on inclusive and semi-inclusive correlations between forward emitted neutrons and charged particles observed in an omnidirectional hodoscope. A total absorption spectrometer was used to detect the neutrons and to measure their energy. Significant correlations are observed over the whole rapidity range. The data suggest that neutrons result from the decay of clusters emitted in the fragmentation region.
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Data obtained from p-p collisions at centre-of-mass energies between 31 and 63 GeV are presented on correlations between momentum analysed forward π − , K − and p and charged particles observed in an omnidirectional hodoscope. The data show that significant correlations are present over the whole rapidity range for all three types of negative particles. The dependence on various kinematic variables suggests a cluster mechanism for the production of particles. In this picture, pions would be produced in clusters emitted in the fragmentation region while K − and p emanate from non-leading clusters.
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Using new data from 100 GeV c π − interactions, we find the energy dependence of the invariant cross-section in the target fragmentation (central) region to be consistent with an A + Bs − 1 2 (C + Ds − 1 4 ) behavior. The leading particle peak near x = + 1 exhibits a width in x which becomes smaller with increasing energy and an integrated cross section which is approximately energy independent.
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