Observation of weak neutral current neutrino production of J/ψJ/\psi

Observation of \jpsi production by neutrinos in the calorimeter of the CHORUS detector exposed to the CERN SPS wide-band \numu beam is reported. A spectrum-averaged cross-section $\sigma^{\mathrm{J/\psi}}$ = (6.3 $\pm$ 3.0) $\times \mathrm{10^{-41}~cm^{2}}$ is obtained for 20 GeV $\leq E_{\nu} \leq$ 200 GeV. The data are compared with the theoretical model based on the QCD Z-gluon fusion mechanism

New results from a search for v(mu) -> v(tau) and v(e) -> v(tau) oscillation

A first analysis of the complete set of data collected by CHORUS in the years 1994-1997 is presented. The search for nu (tau) charged current events has been performed for both leptonic and hadronic decays of the tau lepton. No tau candidate has been found, A nu (tau) --> nu (tau) mixing is excluded down to sin(2)2 theta (mu tau) = 6.8 x 10(-4) for large Deltam(2) (90% C.L.). (C) 2001 Elsevier Science B.V. All rights reserved

New results from a search for v(mu) -> v(tau) and v(e) -> v(tau) oscillation

A first analysis of the complete set of data collected by CHORUS in the years 1994-1997 is presented. The search for nu (tau) charged current events has been performed for both leptonic and hadronic decays of the tau lepton. No tau candidate has been found, A nu (tau) --> nu (tau) mixing is excluded down to sin(2)2 theta (mu tau) = 6.8 x 10(-4) for large Deltam(2) (90% C.L.)

New results from a search for v(mu) -> v(tau) and v(e) -> v(tau) oscillation

A first analysis of the complete set of data collected by CHORUS in the years 1994-1997 is presented. The search for nu (tau) charged current events has been performed for both leptonic and hadronic decays of the tau lepton. No tau candidate has been found, A nu (tau) --> nu (tau) mixing is excluded down to sin(2)2 theta (mu tau) = 6.8 x 10(-4) for large Deltam(2) (90% C.L.)

The CHORUS experiment to search for nu(mu)->nu(tau) oscillation

A new experimental apparatus, designed principally for a high sensitivity search for nu( --> mu(tau) oscillation, has been successfully constructed and made operational by the CHORUS Collaboration for the CERN-WA95 experiment. It consists of a large emulsion target, a scintillating fiber tracker system with optoelectronics read-out, an air-core magnet, a set of trigger hodoscopes, a calorimeter based on the lead/scintillating-fiber technique, and a muon spectrometer. The design, construction and performance of the entire apparatus and of the different detectors are described

A search for nu(mu)->nu(tau) oscillation

CHORUS is an experiment searching for nu(mu) --> nu(tau) oscillation in the CERN wide band neutrino beam with a hybrid setup consisting of a nuclear emulsion target followed by electronic detectors. The experiment has been taking data from 1994 through 1997. A subset of the neutrino interactions collected in 1994 and 1995 have been analyzed, looking for nu(tau) charged current interactions where the tau lepton decays to mu(mu)nu(tau). In a sample of 31,423 nu(mu) charged current interactions, no nu(tau) candidates were found. For large Delta m(mu tau)(2) values, a limit on the mixing angle of sin(2)2 theta(mu tau) < 3.5 x 10(-3) at 90% C.L. can be set, thus improving the previous best result. (C) 1998 Elsevier Science B.V

Final results on νμ→ντ\nu_{\mu} \to \nu_{\tau} oscillation from the CHORUS experiment

The final oscillation analysis of the complete set of data collected by CHORUS in the years 1994-1997 is presented. Reconstruction algorithms of data extracted by electronic detectors were improved and the data recorded in the emulsion target were analysed by new automated scanning systems, allowing the use of a new method for event reconstruction in emulsion. CHORUS has applied these new techniques to the sample of 1996-1997 events for which no muons were observed in the electronic detectors. Combining the new sample with the data analysed in previous papers, the overall sensitivity of the experiment to the $\nu_\tau$ appearance is thus improved. In a two-neutrino mixing scheme, a 90% C.L. upper limit of $\sin^2 2\theta_{\mu\tau} < 4.4 \times 10^{-4}$ is set for large $\Delta m^2$, improving by a factor 1.5 the previously published CHORUS result