D.J. Kocher

Analysis of nucleon structure functions in CERN bubble chamber neutrino experiments

Abstract We present results for the differential cross sections of neutrinos and antineutrinos on nucleons in the energy range E = 2−200 GeV, from the BEBC and Gargamelle experiments. The structure functions F2, 2χF1 and χF3 have been evaluated as a function of χ and q2. Deviations are observed from Bjorken scaling, which are very similar to those found in electron and muon inelastic scattering. For the Callan-Gross ratio, we find 2χF 1 F 2 = 0.80 ± 0.12 and the corresponding value for 〈R〉 = 〈 σ S σ T 〉 = 0.15 ± 0.10 . Our results are consistent with the Gross-Llewellyn-Smith sum rule; we measure ⩾2.5 ± 0.5 valence quarks per nucleon. Quark and antiquark distributions are given. The Nachtmann moments of F2 and χF3 are quantitatively consistent with the predictions from QCD. The value of the strong interaction parameter is λ = 0.74 ± 0.05 GeV without corrections, and 0.66 ± 0.05 GeV including αS2 corrections. The moments of the gluon distribution are found to be positive and indicate an χ distribution of gluons which is comparable with that of the valence quarks.

Observation of Prompt Neutrinos from 400-GeV Proton Nucleus Collisions

Abstract In 70 000 photos taken in BEBC during an experiment in which the 400 GeV proton beam of the CERN SPS was dumped into a massive Cu target 820 m upstream of BEBC, 70 interactions induced by neutral primaries above 10 GeV were observed. In 11 events the secondary charged lepton is an e − , in four events an e + . This number of electron events cannot be due to electron neutrinos from conventional sources (K, Λ, Σ − decays). The flux of the additional (prompt) neutrinos is evaluated. Possible origins are discussed in terms of charmed particles, τs, and as yet undiscovered particles. Limits are given on axion production.

Hadron production in charged current neutrino and antineutrino interactions at high energy

The general features of hadrons produced in charged current interaction of high-energy neutrinos on nucleons are shown to be basically consistent with the idea of quark fragmentation within the framework of the quark parton model. However, many of the effects observed are shown also to follow from longitudinal phase space. Evidence is presented for a rise in 〈pT2〉 with Q2 in qualitative agreement with the predictions of quantum chromodynamics (QCD).

Total cross sections for charged-current neutrino and antineutrino interactions in BEBC in the energy range 20–200 GeV

Abstract The charged-current cross sections for neutrinos and antineutrinos on nucleons in the energy range 20–200 GeV are given. Taken in conjunction with the previous Gargamelle results, they show that σ E is almost constant with energy for antineutrinos, and falls with energy for neutrinos. The value of 〈q 2 〉 E decreases with energy for both neutrinos and antineutrinos, and these deviations from exact Bjorken scaling are consistent with those observed in electron and muon inelastic scattering. We find no evidence for new heavy quark states with right-handed coupling.

Simplicity of “transverse energy” spectra of hadrons

Abstract Using data from a 16 GeV/c π+p bubble chamber experiment, we have studied the production of pions and meson resonances in the central region. Transverse spectra have been analysed in terms of the transverse energy variable Et=√pt2+M2. We find that the Et spectra of “stable” particles, of resonances like ϱ, ω and f, and of corresponding non-resonant two- and three-pion systems all follow one simple exponential in Et over several orders of magnitude in cross section. All spectra are consistent with one common slope parameter of approximately (120 MeV)−1.

Di-Lepton events in the BEBC narrow-band beam neutrino experiment

Abstract In film taken with BEBC filled with a Ne(74%mol)/H 2 mixture and exposed to the CERN narrow-band neutrino beam (200 GeV), tenμ − μ + , one μ − μ + μ − and five μ − e + events were found in the ν exposure and two μ + μ − events and one μ + e − event in the ν exposure. Assuming the same production mechanism for μμ and μe events, the relative rates, corrected for identification inefficiency and background, can be combined and are (1.3 ± 0.4)% for (μ − e + + μ − μ + )/μ − in neutrino interactions, and (1.2 ± 0.5)% for (μ + e − + μ + μ − )/μ + antineutrino interactions. Eight out of the sixteen μ − l + events have a V 0 , leading to a corrected K 0 -multiplicity of 1.7 ± 0.7. No evidence is found for heavy-lepton production.

The structure of the weak neutral current: An analysis of the hadronic energy distribution from neutrino and antineutrino interactions

Abstract An analysis is presented of the distribution of hadronic energy in neutrino and antineutrino neutral current interactions occurring in BEBC, filled with a neon-hydrogen mixture and exposed to the CERN-SPS narrow-band neutrino beam. This shows that the contributions by scalar or pseudo-scalar forms of the interaction are consistent with zero and pure V, A and V + A are excluded; there is good agreement with the Weinberg-Salam model.

K∗(890) production in K−p → NKπ at 16 GeV/c

Results on K∗(890) production in K−p → NKπ reactions at 16 GeV/c are presented. Total cross sections, differential cross sections and density matrix elements are determined. It is found that: (i) The cross section for K∗−(890) p is consistent with containing two components, one due to natural parity exchange, falling slowly with increasing energy, the other, due to unnatural parity exchange, vanishing rapidly with increasing energy. For K∗o(890)n, the cross section decreases steadily as the energy increases. (ii) Natural spin-parity exchange dominates in the K∗−(890) p channel, the unnatural exchange contribution being approximately (5±4)%. In K∗o(890)n, natural spin-parity exchange is only about (30±10)%. (iii) The reacton K−p → K∗−(890)p is dominated (95±5)% by isoscalar exchange. (iv) The effective trajectory involved in the I = 0 natural parity exchange is consistent with the ω-f trajectory. (v) Interference terms between exchanges with positive (f, πo,…) and negative (ϱo, ω,…) C-conjugation amount to (23±12) μb at 16 GeV/c.

Cross sections for neutrino and antineutrino neutral current interactions

Abstract The cross sections for ν and ν neutral current interactions for which the hadron energy is >15 GeV have been measured. These results, and the ratios of neutral current to charged current cross sections, are in agreement with the Weinberg-Salam model. Values of sin 2 θ W have been obtained both with and without the use of a parameterisation for the hadronic part of the interaction; the values are in good agreement with each other and the preferred result, that obtained by the method independent of hadronic models, is sin 2 θ W = 0.22 ± 0.05.

An impact parameter analysis of multiparticle production in medium-energy meson-proton interactions

Abstract Lower bounds can be calculated for the root-mean-square impact parameter b , in any exclusive reaction. These lower bounds, b L , have been calculated for 9 exclusive π − p reactions at 16 GeV/ c and for 24 exclusive K − p reactions at 10 and 16 GeV/ c . It is found that b L decreases with increasing multiplicity, but is larger at higher energy. The values of b L are larger for diffractive than for non-diffractive channels of the same multiplicity.