I. Butterworth

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.

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).

Further study of the prompt neutrino flux from 400 GeV proton-nucleus collisions using BEBC

Abstract In a second beam-dump experiment using BEBC the prompt neutrino flux has been measured and its characteristics studied. The use of targets of variable effective density allowed a determination of the conventional decay neutrino flux and a direct demonstration of a prompt neutrino signal. Assuming that the prompt neutrinos originate in the decay of charmed D mesons then a production cross section is estimated. An upper limit of 10% can be set to the proportion of interactions induced by τ neutrinos.

Total cross sections νμ and ḡnμcharged-current interactions between 20 and 200 GeV

Abstract Exposures of the Ne/H 2 filled Big European Bubble Chamber (BEBC) to a dichromatic neutrino (antineutrino) beam produced by 400 GeV protons of the CERN SPS yielded ∼ 3100 events with a negative, and ∼ 1100 with a positive, muon. The neutrino flux is determined from the muon flux in the shielding. Assuming a linear energy dependence of the cross section, the values σ E between 20 and 200 GeV are found to be 0.657 ± 0.012 (stat.) ± 0.027 (syst.) and 0.309 ± 0.009 (stat.) ± 0.013 (syst.) cm 2 (GeV nucleon) −1 , for neutrinos and antineutrinos, respectively. The scaling variable q 2 E decreases significantly with increasing energy both for neutrinos and antineutrinos.

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.

Strange Particle Production in Neutrino and Anti-neutrino Neon Interactions

The inclusive production of K0s and Λs has been investigated in neutrino and antineutrino interactions in BEBC, filled with a neon-hydrogen mixture. The inclusive rates for the 3083 (1022) ν (ν) induced charged current events are (23.0 ± 1.7)% ((21.9 ± 2.8)%) for K0s and (5.7 ± 0.7)% ((6.5 ± 1.2)%) for Λs. The general behaviour of the K0s and Λs is found to be similar to that in νp interactions and π+p interactions at lower 〈W〉. In the hadronic c.m.s. K0s are produced mostly forwards, Λs predominantly in the backward hemisphere. The data indicate that K0s produced in ν interactions on average carry a larger fraction of the total available momentum than those in ν induced reactions. The dependences of the average transverse momentum on the variables Q2, W2 and Bjorken x are presented.

A test of ν stability using a 200 GeV narrow-band neutrino beam at BEBC

Abstract ν e induced events obtained in a 200 GeV narrow-band beam have been studied and compared to the number expected from K e3 + decay. Agreement is found between the expected and observed numbers allowing limits to be set on ν e → ν x mixing.

Transverse momentum of hadrons produced in ν and ν interactions on an isoscalar target in BEBC

The average transverse momentum squared, 〈p⊥2〉, of hadrons is studied as a function of W2 and of Q2 for ν and ν interactions on an isoscalar target. An increase of 〈p⊥2〉 with W2 is observed for the hadrons emitted forward in the hadronic c.m.s. The p⊥ dependence of the fragmentation function is found to factorise from the structure function at fixed W, but does not factorise at fixed Q2. Unlike the case of forward-going particles, the 〈p⊥2〉 of hadrons going backward in the c.m.s. shows no strong dependence on W2.

Resonance production in K−-neutron interactions at K− momenta of 1.45 and 1.65 GeV/c

Abstract Results are reported on K − -neutron interactions at c.m. energies near 2 GeV. The interactions are dominated by strong production of hyperon resonances, particularly Σ(1385), Λ(1405) and Λ(1520). Production cross sections and angular distributions are given for the Σ(1385), Λ(1405) and Λ(1520) and branching fractions to decay modes observed in the experiment are given for Σ(1385) and Λ(1520). The strong energy dependence of some features of the data suggests that s -channel effects are dominant.

A partial wave analysis of the reaction K−n → π−Λ in the C.M. energy region from 1900 MeV to 2100 MeV

Abstract Results are presented for a partial wave analysis of the reaction K − n → π − Λ covering a range of c.m. energies from 1900 to 2100 MeV. The events used were obtained from interactions of the type K − n → π − Λp s . The analysis was performed both for a sample of events where p s , the spectator proton from the deuteron, was seen, and for all events. Good agreement was found between the two sets of results. Values of the resonance parameters of the Σ(2030) were determined, and some evidence was found supporting the existence of the F5 Σ(1915). In addition, the P3 amplitude was found to be rapidly changing near 2100 MeV, consistent with a resonance in this wave at 2080 MeV.