24 research outputs found
Leading order analysis of neutrino induced dimuon events in the CHORUS experiment
We present a leading order QCD analysis of a sample of neutrino induced
charged-current events with two muons in the final state originating in the
lead-scintillating fibre calorimeter of the CHORUS detector. The results are
based on a sample of 8910 neutrino and 430 antineutrino induced opposite-sign
dimuon events collected during the exposure of the detector to the CERN Wide
Band Neutrino Beam between 1995 and 1998. % with GeV
and GeV collected %between 1995 and 1998. The analysis yields a
value of the charm quark mass of \mc = (1.26\pm 0.16 \pm 0.09) \GeVcc and a
value of the ratio of the strange to non-strange sea in the nucleon of , improving the results obtained in similar analyses
by previous experiments.Comment: Submitted to Nuclear Physics
Associated Charm Production in Neutrino-Nucleus Interactions
In this paper a search for associated charm production both in neutral and
charged current -nucleus interactions is presented. The improvement of
automatic scanning systems in the {CHORUS} experiment allows an efficient
search to be performed in emulsion for short-lived particles. Hence a search
for rare processes, like the associated charm production, becomes possible
through the observation of the double charm-decay topology with a very low
background. About 130,000 interactions located in the emulsion target
have been analysed. Three events with two charm decays have been observed in
the neutral-current sample with an estimated background of 0.180.05. The
relative rate of the associated charm cross-section in deep inelastic
interactions, has been
measured. One event with two charm decays has been observed in charged-current
interactions with an estimated background of 0.180.06 and the
upper limit on associated charm production in charged-current interactions at
90% C.L. has been found to be .Comment: 10 pages, 4 figure
Charged-Particle Multiplicities in Charged-Current Neutrino-- and Anti-Neutrino--Nucleus Interactions
The CHORUS experiment, designed to search for
oscillations, consists of a nuclear emulsion target and electronic detectors.
In this paper, results on the production of charged particles in a small sample
of charged-current neutrino-- and anti-neutrino--nucleus interactions at high
energy are presented. For each event, the emission angle and the ionization
features of the charged particles produced in the interaction are recorded,
while the standard kinematic variables are reconstructed using the electronic
detectors. The average multiplicities for charged tracks, the pseudo-rapidity
distributions, the dispersion in the multiplicity of charged particles and the
KNO scaling are studied in different kinematical regions. A study of
quasi-elastic topologies performed for the first time in nuclear emulsions is
also reported. The results are presented in a form suitable for use in the
validation of Monte Carlo generators of neutrino--nucleus interactions.Comment: 17 pages, 5 figure
Measurement of charm production in neutrino charged-current interactions
The nuclear emulsion target of the CHORUS detector was exposed to the
wide-band neutrino beam of the CERN SPS of 27 GeV average neutrino energy from
1994 to 1997. In total about 100000 charged-current neutrino interactions with
at least one identified muon were located in the emulsion target and fully
reconstructed, using newly developed automated scanning systems. Charmed
particles were searched for by a program recognizing particle decays. The
observation of the decay in nuclear emulsion makes it possible to select a
sample with very low background and minimal kinematical bias. 2013
charged-current interactions with a charmed hadron candidate in the final state
were selected and confirmed through visual inspection. The charm production
rate induced by neutrinos relative to the charged-current cross-section is
measured to be sigma(nu_mu N -> mu- C X)/sigma(CC) = (5.75 +-0.32 stat +-0.30
syst)%. The charm production cross-section as a function of the neutrino energy
is also obtained. The results are in good agreement with previous measurements.
The charm-quark hadronization produces the following charmed hadrons with
relative fractions (in %): f_Dzero = 43.7+-4.5, f_Lambda_c^plus = 19.2+-4.2,
f_Dplus = 25.3+-4.2, and f_D_splus = 11.8+-4.7.Comment: 16 pages, 5 figure
Measurements of production and of decay branching fractions in neutrino nucleon scattering
During the years 1994-97, 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 D^0 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 D^0 into four-charged particles to two charged particles was measured to B(D^0 -> V4) / B(D^0 -> V2) = 0.207+- 0.004. The inclusive measurement of the observed production rate of the D^0 with a decay into four charged prongs in combination with external measurements of this topological branching ratio was used to determine the total D^0 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 \sigma(D^0) / \sigma(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-prongs events the branching ratio into six charged particles was determined to be (1.2^1.3_-0.9 +- 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