Large-angle π±p elastic-scattering cross sections, measured between 2 and 9 GeV/c in fine intervals of incident momentum and scattering angle, are used to search for cross-section fluctuations occurring for small changes in the center-of-mass energy as suggested by Ericson and Mayer-Kuckuck and by Frautschi. Significant fluctuations are observed.
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We present data on the reaction ν p → μ + pπ − from an exposure of the Fermilab 15 ft hydrogen bubble chamber. The channel cross section for 5 GeV < E ν < 70 GeV and M( p π − ) < 1.9 GeV is σ = (27 ± 5) × 10 −40 cm 2 . This cross section is dominated by the I = 1 2 production amplitude.
We have measured the inclusive production of J ψ in 16 and 22 GeV π − copper collisions in a wide aperture magnetic spectrometer. The cross section per Cu nucleus for x > 0 corrected for branching ratio is 64 ± 38 nb at 16 GeV and 196 ± 38 nb at 22 GeV. As threshold is approached, the mean values of the Feynman x distribution increase and the cross section for J ψ production drops steeply. This can be understood in terms of the quark-fusion model where the antiquark content of the pion makes an increasingly significant contribution as M 2 s increases.
We have made a measurement of the lepton charge asymmetry in KL0 decays. Magnetic analyses of the decay products in a spectrometer using multiwire proportional counters allowed kinematic reconstruction of the event where the particles traversed only 293 mg of matter. The leptons were differentiated from the pions only through their different transverse-momentum distributions. The asymmetry was measured to be (3.33 ± 0.50) × 10−3, in accord with the superweak description of CP nonconservation.
We present results on flux-normalized neutrino and antineutrino cross sections near y=0 from data obtained in the Fermilab narrow-band beam. We conclude that values of σ0=dσdy|y=0 are consistent with rising linearly with energy over the range 45<~Eν<~20.5 GeV. The separate averages of ν and ν¯, each measured to 4%, are equal to well within the errors. The best fit for the combined data gives σ0E=(0.719±0.035)×10−38 cm2/GeV at an average Eν of 100 GeV.
Measurements of flux-normalized neutrino and antineutrino total charged-current cross sections (σ) in the energy range 45<E<205 GeV are presented. We see no evidence for the anomalous sharp rise in σν¯σν reported by earlier authors. The neutrino cross section rises linearly with energy and with σE about 18% smaller than other measurements below 10 GeV. The average antineutrino slope at 55 GeV is consistent with measurements at low energy; however, a (20 ± 10)% increase is indicated over our energy range.
We have measured charged-particle production in neutron-nucleus collisions at high energy. Data on positive and negative particles produced in nuclei [ranging in atomic number (A) from beryllium to lead] are presented for essentially the full forward hemisphere of the center-of-mass system. A rough pion-proton separation is achieved for the positive spectra. Fits of the form Aα to the cross sections are presented as functions of transverse momentum, longitudinal momentum, rapidity, and pseudorapidity. It is found that α changes from ∼0.85 to ∼0.60 for laboratory rapidities ranging from 4 to 8. Trends in the data differ markedly when examined in terms of pseudorapidity rather than rapidity. Qualitatively, the major features of our data can be understood in terms of current particle-production models.
We have observed muons produced directly in Cu and W targets by 300-GeV incident protons. We find a yield of muons which is approximately a constant fraction (0.8·10−4) of the pion yield for both positive and negative charges and for transverse momenta between 1.5 and 5.4 GeV/c.
A partial-wave analysis of the diffractively produced p π + π − system has been performed for the reaction K − p→K − (p π + π − ) at 10, 14.3 and 16 GeV/ c using the isobar model. For p π + π − masses below 1.6 GeV, the system can be described by the states with spin-parity 1 2 + and 3 2 − . The dominant state is the 3 2 − S-wave Δπ . No evidence for resonance production can be found here. For higher masses, the states 5 2 + and 5 2 − are present in addition. The 5 2 − constitutes a violation of the Gribov-Morrison rule and its mass shape is consistent with being the D 15 N ∗ (1670) resonance. The peak in the p π + π − mass spectrum at 1.7 GeV cannot be explained by one single spin-parity state. A comparison of the diffractive reaction pomeron + p → p ππ with the formation experiment π p → N ππ is made.
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