The rate of neutrino- and antineutrino-induced prompt same-sign dimuon production in steel was measured using a sample of μ−μ− events and 25 μ+μ+ events withPμ>9 GeV/c, produced in 1.5 millionvμ and 0.3 million\(\overline {v_\mu}\) induced charged-current events with energies between 30 GeV and 600 GeV. The data were obtained with the Chicago-Columbia-Fermilab-Rochester (CCFR) neutrino detector in the Fermilab Tevatron Quadrupole Triplet Neutrino Beam during experiments E 744 and E 770. After background subtraction, the prompt rate of same-sign dimuon production is (0.53±0.24)×10−4 pervμ charged-current event and (0.52±0.33)×10−4 per\(\overline {v_\mu}\) charged-current event. The kinematic distributions of the same-sign dimuon events after background subtraction are consistent with those of the non-prompt background due to meson decays in the hadron shower of a charged-current event. Calculations ofc\(\bar c\) gluon bremsstrahlung, based on improved measurements of the charm mass parameter and nucleon structure functions by the CCFR collaboration, yield a prompt rate of (0.09±0.39)×10−4 pervμ charged-current event. In this case,c\(\bar c\) gluon bremsstrahlung is probably not an observable source of prompt same-sign dimuons.
The final results from the WA 1/2 neutrino experiment in the 1984 CERN 160 GeV narrow band beam are presented. The ratiosRν and\(R_{\bar v} \) of neutral to charged current interaction rates of neutrinos and antineutrinos in iron are measured to beRν=0.3072±0.0033 and\(R_{\bar v} \)=0.382±0.016. A value of the electroweak parameter sin2 θw = 1 −mW2/mZ2 is extracted fromRν. The result is sin2 θw =0.228+0.013(mc−1.5)±0.0003 (theor.) wheremc is the mass of the charmed quark in GeV formt=60 GeV,MH=100 GeV, ρ=1. CombiningRν and\(R_{\bar v} \) one obtains a value for ρ=0.991+0.023(mc−1.5)±0.020(exp.). Alternatively,Rν and\(R_{\bar v} \) yield a precise value of the ratio of intermediate vector boson massesmW/mZ=0.880−0.007(mc−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,gL2 andgR2, are determined.
Distributions of the Bjorken scaling variables x and y, and the structure function F+(x), are presented both for neutral-current and for charged-current νμ interactions. The data were obtained by use of the Fermilab 15-ft neon bubble chamber exposed to a narrow-band νμ beam. Results are based on 151 neutral-current and 683 charged-current events. An important feature of the neutral-current analysis is the event-by-event reconstruction of the outgoing neutrino.
We report a measurement of the electroweak parameters sin2θw and ϱ based on the ratios of neutral current to charged current events measured in the Fermilab narrow-band neutrino beam at energies of 30–240 GeV. The data are fully corrected for radiative effects, heavy-quark production, and other effects. The best value for sin2θw obtained, sin2θw=0.239±0.011, is consistent with the most recent values fromW andZ production, as well as from other neutrino experiments.
We present measured hadron energy distributions for the reactions ν(ν¯)+N→ν(ν¯)+hadrons at high energy, as well as for the similar charged-current interactions. Insofar as possible, the determination of these distributions avoids any a priori assumptions about either the neutral-current or the charged-current interactions. We further analyze the neutral-current distributions within the framework of specific models, particularly the scaling model, to obtain a positive-helicity component P=0.36±0.10, which lies between pure V−A and pure V or A, and a coupling strength of g0=0.31±0.03 relative to the charged-current interaction. These coupling parameters agree well with the predictions of the Weinberg-Salam model with sin2θW=0.33±0.07.
The ratio Rν 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 neutrino narrow-band beam at the CERN Super Proton Synchrotron. The result is Rν=0.3072±0.0025(stat)±0.0020(syst), for hadronic energy greater than 10 GeV. The electroweak mixing parameter is sin2θW=0.225±0.005(expt)±0.003(theor)+0.013(mc−1.5 GeVc2), where mc is the charm-quark mass.
The production of μe-pairs is studied in interactions of neutrinos with nuclei of heavy freon in the SKAT bubble chamber experiment. A rate of μ−e+ to charged current interactions above the charm threshold of\(R^{\mu ^ -e^ +}= (4.6 \pm 1.2) \cdot 10^{ - 3} \) is found. The properties of the observed μ−e+ events can be well described by assuming them to originate from the semileptonic decay of quasielastic produced charmed baryonsΛc and inclusive charmedD-meson production. The rates for these reactions are found to be (6.7±3.5)×10−2 and (2.5±0.9)×10−2, respectively. A total charmed particle production rate of (9.2±3.6)×10−2 is calculated.
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We report on the analysis of inclusive neutral current events produced in neutrino and antineutrino narrow band beams. We find for incident neutrino energies in the range 12–200 GeV and for hadron energies above 12 GeV a neutral to charged current cross-section ratio of R v = 0.293 ± 0.010 for incident neutrinos, and R v = 0.35 ± 0.03 for antineutrinos. These ratios are consistent with the Weinberg-Salam model, with sin 2 θ w = 0.24 ± 0.02.
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