Faisceau intense de mésons μ— de grande pureté

A focusing and analyzing device, 24 quadrupole lenses with an alternating gradient magnet, has been constructed near the C. E. R. N. synchrocyclotron. It provides strong fluxes of μ— mesons (about 104 μ—/sec on a 10 × 10 cm2 target) with a low π meson contamination (1 % or less) for high and low energy.Un dispositif de focalisation et d'analyse constitué d'un ensemble de 24 lentilles quadrupolaires magnétiques, et d'un électro-aimant à focalisation forte est en fonctionnement auprès du synchro-cyclotron du C. E. R. N. On donne l'intensité du faisceau de mésons μ— obtenu (environ 10 4 μ—/s dans une cible de 10 × 10 cm2) et la contamination en mésons π— (de l'ordre de 1 %) pour différentes bandes d'énergie. On cite les utilisateurs actuels de ce faisceau

A new measurement of the cross section of the inverse muon decay reaction νμ\nu_{\mu} + e−^{-} --> μ−\mu^{-} + νe\nu_{e}

We have measured the cross section for inverse muon decay in the CERN neutrino wide band beam

Search for heavy isosinglet neutrinos

A new search for decays of heavy isosinglet neutrinos produced by neutral-current neutrino interactions in the CERN wide-band neutrino beam has been conducted by the CHARM-II Collaboration. We searched for heavy neutrinos created by scattering muon neutrinos on nucleons and decaying into μ+μ-νμ. Production and decay of heavy neutrinos would appear as double events in the detector. Each double event candidate was tested wheather the measured quantities are compatible with the kinematics of this process. No event passed this test. The analysis is based on 2 × 107 neutral-current neutrino events collected from 1987-1991

Flavour universality of neutrino couplings with the Z

We are reporting the first experimental result of the coupling of the muon neutrino with the Z. This result is in good agreement with the average value of the coupling of the three neutrino families as derived from the invisible decay width of the Z. We also determined gντ assuming Nν=3. © 1994.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

SEARCH FOR HEAVY ISOSINGLET NEUTRINOS

A new search for decays of heavy isosinglet neutrinos produced by neutral-current neutrino interactions in the CERN wide-band neutrino beam has been conducted by the CHARM-II Collaboration. We searched for heavy neutrinos created by scattering muon neutrinos on nucleons and decaying into mu(+) mu(-) v(mu). Production and decay of heavy neutrinos would appear as double events in the detector. Each double event candidate was tested wheather the measured quantities are compatible with the kinematics of this process. No event passed this test. The analysis is based on 2 x 10(7) neutral-current neutrino events collected from 1987-1991. The experiment is sensitive to heavy neutrinos in the mass range 0.3-2.4 GeV/c(2). The best limit for the mixing parameter is \U-mu i\(2) < 3 X 10(-5) for a mass around 2 GeV/c(2). The analysis improved by an order of magnitude previous results derived from wide-band neutrino beam exposures of the CHARM detector

A new determination of the electroweak mixing angle from muon-neutrino-electron scattering

We are reporting on a new determination of sin2θ{symbol}w from the ratio of vμe to ve scattering cross sections. A new detector designed for this purpose was exposed tothe Wide Band Neutrino Beamof the 450 GeV (CERN SPS. An analysis of data taken in 1987 and 1988 is presented based on 762 vμe and 1017 ve events. From the ratio of σ(vμe) to σ(vμe) we determined sin2θ{symbol}w=0.233±0.012 (stat) ± 0.008 (syst) without radiative correction. With radiative correction for mt=mH=100 GeV we find sin2θ{symbol}w=0.232±0.012(stat) ±0.008(syst). © 1989.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

An improved determination of the electroweak mixing angle from muon-neutrino electron scattering

We are reporting an improved determination of the electroweak mixing angle sin2Θw from the ratio of νμe to νμe scattering cross sections. The CHARM II detector was exposed to neutrino and antineutrino wide band beams at the 450 GeV CERN SPS. Including new data collected in 1989 we have obtained 1316 ± 56 νμe and 1453 ± 62 νμe events. From the ratio of the visible cross sections we determined sin2Θ0=0.239 ± 0.009(stat) ± 0.007(syst) without radiative corrections and gVe gAe=0.047 ± 0.046. Combining this last result with recent results on gAe at LEP we obtain gVe= -0.023 ± 0.023. © 1991.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Precision measurement of electroweak parameters from the scattering of muon-neutrinos on electrons

We report final results on electroweak parameters from muon-neutrino electron scattering observed in the CHARM II detector from 1987 till 1991. In total 2677±82 and 2752±88 neutrino-electron scattering events have been detected in the ν and ν-beam, respectively. From the ration of differential cross sections we obtain for the electroweak mixing angle sin2 Θ = 0.2324±0.0083. From the absolute neutrino-electron scattering event rate we determined the effective vector and axial-vector neutral current coupling constants to be gVve = -0.035±0.017 and gAve = -0.503±0.017. © 1994.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe