The CHORUS honeycomb tracker and its bitstream electronics

The CHORUS experiment searches for nu(mu)nu(tau) oscillation. To aid in the momentum reconstruction of charged hadrons, a honeycomb tracker was built with three orientations of six planes each. The planes are manufactured by point-welding together two precision folded conductive polycarbonate foils, forming hexagonal tubes with 30 mu m thick anode wires in the center. The honeycomb tracker in CHORUS is read out using a bitstream principle. The amplified signal of each wire is binary sampled every 5 ns and stored in a 256 bit circular buffer, implemented in dual-port memories. This technique allows a full reconstruction of a 1.28 mu s history of each wire. Eighteen cards, each handling 72 wires, are read out over a single flat cable using a card-to-card pipeline. (C) 1998 Elsevier Science B.V. All rights reserved

The trigger system of the CHORUS experiment

A new apparatus for detection of nu(mu) --> nu(tau) oscillation has been successfully constructed and operated by the CHORUS Collaboration for the CERN-WA95 experiment. The design, implementation and performance of the electronic trigger system is described. A trigger efficiency of 99% was measured for nu(mu) charged-current events and 90% for neutral-current events. (C) 1999 Elsevier Science B.V. All rights reserved. RI Ludovici, Lucio/F-5917-201

The trigger system of the CHORUS experiment

A new apparatus for detection of nu(mu) --> nu(tau) oscillation has been successfully constructed and operated by the CHORUS Collaboration for the CERN-WA95 experiment. The design, implementation and performance of the electronic trigger system is described. A trigger efficiency of 99% was measured for nu(mu) charged-current events and 90% for neutral-current events

The data acquisition system of the CHORUS experiment

In the years 1994-1998 the CHORUS Collaboration has recorded data in the CERN WA95 experiment. Here we describe the data acquisition system that has been used, featuring concurrent hierarchical state machines, a remote operating system, a buffer manager, a dispatcher, a control panel and a supervisor. (C) 2002 Elsevier Science B.V. All rights reserved

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

Measurements of D-0 production and of decay branching fractions in neutrino-nucleon scattering

During the years 1994-1997, the emulsion target of the CHORUS detector was exposed to the wide-band neutrino beam of the CERN SPS of 27 GeV average neutrino energy. In total about 100 000 charged-current neutrino interactions were located in the nuclear emulsion target and fully reconstructed. From this sample of events which was based on the data acquired by new automatic scanning systems, 1048 charged-current interactions with a Do in the final state were selected by a pattern recognition program and confirmed as neutral-particle decays through visual inspection. The ratio of decay branching fractions of the Do into four charged particles to two charged particles was measured to be B(D-0 → V4)/B(D-0 → V2) = 0.207 ± 0.016 ± 0.004. The inclusive measurement of the observed production rate of the Do with a decay into four charged prongs in combination with external measurements of this topological branching ratio was used to determine the total Do production rate by neutrinos without additional assumption on the branching fractions. The value of this rate relative to the charged-current cross-section was found to be σ (D-0) / σ (CC) = 0.0269 ± 0.0018 ± 0.0013. In addition, the same normalization method was used to deduce the inclusive topological decay rate into final states with neutral particles only. A value of 0.218 ± 0.049 ± 0.036 was found for this branching fraction. From an observed number of three charged six-prong events the branching ratio into six charged particles was determined to be (1.2(-0.9)(+1.3) ± 0.2) x 10(-3). A measurement of the energy dependence of the D-0 production by neutrinos relative to the total charged-current cross-section is also reported. This measurement was used to deduce for m(c), the effective charm-quark mass, a value of (1.42 ± 0.08) GeV/c(2). © 2005 Elsevier B.V. All rights reserved

Measurement of D*(+) production in charged-current neutrino interactions

During the years 1994-1997, the emulsion target of the CHORUS detector was exposed to the wide-band neutrino beam of the CERN SPS of 27 GeV average neutrino energy. In total about 100 000 charged-current neutrino interactions were located in the nuclear emulsion target and fully reconstructed. A high-statistics sample of neutrino interactions with a Do in the final state was collected. Using the decay mode D*(+) -> D(0)pi(+) a production cross-section measurement of the D*+ in neutrinonucleon charged-current interactions was performed. The low Q-value of the decay was used to isolate a sample of candidate events containing a positive hadron with a small PT with respect to the DO direction. A signal of 22.1 +/- 5.5 D*+ events was obtained. The D*(+) production cross-section relative to the D-0 production cross-section, sigma(D*(+))/sigma (D-0), was estimated to be 0.38 +/- 0.09(stat) +/- 0.05(syst). From this result, the fraction of Do's produced via the decay of a D* was deduced to be 0.63 +/- 0.17. The D*(+) production cross-section relative to the nu(mu) charged-current interaction, sigma(D*(+))/sigma(CC), was estimated to be [1.02 +/- 0.25(stat) +/- 0.15(syst)]%. (c) 2005 Elsevier B.V. All rights reserved. RI Ludovici, Lucio/F-5917-2011; De Rosa, Gianfranca/E-8737-2012; Fiorillo, Giuliana/A-2248-201

Experimental study of trimuon events in neutrino charged-current interactions

This Letter reports on a study of trimuon events induced by neutrino interactions in the CHORUS calorimeter exposed to the CERN SPS wide-band v(mu) beam. Among the multimuon events produced in the calorimeter, 42 mu(-) mu(-) mu(+) events were selected and their kinematical properties investigated. In the past, several groups collected a sample of about one hundred events of this type but their source was largely unknown. Taking advantage of experimental data presently available on the production and muonic branching ratios of light neutral mesons and resonances, we make absolute predictions for the expected rates in our experiment. Detailed Monte Carlo simulations described in this article show that more than half of the trimuon events can be attributed to this source. Muons from pi- and K- decays in charm dimuon events are responsible for an additional approximate to 25% contribution to the total mu(-)mu(-)mu(+) rate. The remaining 25% of events are likely to come from the internal bremsstrahlung of virtual photons into a muon pair. Associated-charm production with subsequent decays of both charmed particles into muons is a negligible source of trimuon events. (C) 2004 Elsevier B.V. All rights reserved. RI Doucet, Mathieu/A-5333-2010; Ludovici, Lucio/F-5917-2011; De Rosa, Gianfranca/E-8737-2012; Fiorillo, Giuliana/A-2248-201