Search

A study of prompt neutrino events from 400 GeV protons on a beam-dump is presented. The ratio of electron- to muon-neutrino rates is 0.86±0.14, in agreement withe−μ universality. The anti-neutrino to neutrino flux ratio is $$\bar v_\mu /v_\mu = 0.81 \pm 0.19$$ . The absolute rates and distributions observed are shown to be in quantitative agreement with the known properties of charmedquark production in hadron collisions.

A high-statistics measurement of the differential cross-sections for neutrino-iron scattering in the wide-band neutrino beam at the CERN SPS is presented. Nucleon structure functions are extracted and theirQ 2 evolution is compared with the predictions of quantum chromodynamics.

Neutrino and antineutrino total charged current cross sections on iron were measured in the 100, 160, and 200 GeV narrow band beams at the CERN SPS in the energy range 10 to 200 GeV. Assuming σ/E to be constant, the values corrected for non-isoscalarity are σv/E = (0.686 ± 0.019) * 10−38 cm2/ (GeV · nucleon) and σv/E = (0.339 ± 0.010) * 10−38 cm2/ (GeV·nucleon). Between 50 and 150 GeV no energy dependence of σ/E was observed within ±3% for neutrino and ±4% for antineutrino interactions.

We have searched for ν μ oscillations by comparing the rates of ν gm charged-current interactions in two detectors located 130 and 885 m from the target, which was struck by a 9.2 GeV/ c proton beam from the CERN Proton Synchroton. No evidence for ν μ oscillations was found. At the 90% confidence level, Δm 2 values between 0.26 and 90 eV 2 are excluded for maximal mixing. The most restrictive limit on the neutrino mixing-angle parameter sin 2 2 θ is 0.053 at Δm 2 =2.5 eV 2 .

From exposures of the CDHS detector at the CERN SPS we have obtained 367μ + μ − events in neutrino beams and 73μ + μ + events in an antineutrino beam. The magnitude of a prompt like-sign signal has been controversial in the past and moreover could not be explained by known production mechanisms. A critical discussion of the experimental situation is given. We have tried to reduce the systematic uncertainties of previous experiments and to get more information on the dependence of the signal with energy and the muon momentum cut-off. This experiment yields a signal of 2.8σ (2.4σ) of prompt like-sign dimuon events in the case of neutrinos (antineutrinos). The rate to charged current events is of the order of 10−4 forp μ 100 GeV. The prompt signal has all the properties expected from the production and decay of charm-anticharm events. The magnitude, however, is substantially higher then the prediction of perturbative QCD but lower than some other experiments.

The ratio R-italic/sub ..nu../ of the neutral- to charged-current cross sections of neutrinos in iron has been measured in an exposure of the CERN-Dortmund-Heidelberg-Saclay neutrino detector to a 160-GeV/c-italic neutrino narrow-band beam at the CERN Super Proton Synchrotron. The result is R-italic/sub ..nu../ = 0.3072 +- 0.0025(stat) +- 0.0020(syst), for hadronic energy greater than 10 GeV. The electroweak mixing parameter is sin/sup 2/theta/sub W/ = 0.225 +- 0.005(expt ) +- 0.003(theor)+0.013(m-italic/sub c-italic/-1. 5 GeV/c-italic/sup 2/), where m-italic/sub c-italic/ is the charm-quark mass.

The final results from the WA 1/2 neutrino experiment in the 1984 CERN 160 GeV narrow band beam are presented. The ratiosR ν and\(R_{\bar v} \) of neutral to charged current interaction rates of neutrinos and antineutrinos in iron are measured to beR ν=0.3072±0.0033 and\(R_{\bar v} \)=0.382±0.016. A value of the electroweak parameter sin2 θ w = 1 −m W 2 /m Z 2 is extracted fromR ν. The result is sin2 θ w =0.228+0.013(m c −1.5)±0.0003 (theor.) wherem c is the mass of the charmed quark in GeV form t =60 GeV,M H =100 GeV, ρ=1. CombiningR ν and\(R_{\bar v} \) one obtains a value for ρ=0.991+0.023(m c −1.5)±0.020(exp.). Alternatively,R ν and\(R_{\bar v} \) yield a precise value of the ratio of intermediate vector boson massesm W /m Z =0.880−0.007(m c −1.5)±0.002(exp.)±0.002(theor.). Comparison of these results with those from direct measurements of the vector boson masses are presented. In a model-independent analysis the left- and right-handed neutral current coupling constants,g L 2 andg R 2 , are determined.