596 research outputs found
Search for the exotic resonance in the NOMAD experiment
A search for exotic Theta baryon via Theta -> proton +Ks decay mode in the
NOMAD muon neutrino DIS data is reported. The special background generation
procedure was developed. The proton identification criteria are tuned to
maximize the sensitivity to the Theta signal as a function of xF which allows
to study the Theta production mechanism. We do not observe any evidence for the
Theta state in the NOMAD data. We provide an upper limit on Theta production
rate at 90% CL as 2.13 per 1000 of neutrino interactions.Comment: Accepted to European Physics Journal
Production properties of K*(892) vector mesons and their spin alignment as measured in the NOMAD experiment
First measurements of K*(892) mesons production properties and their spin
alignment in nu_mu charged current (CC) and neutral current (NC) interactions
are presented. The analysis of the full data sample of the NOMAD experiment is
performed in different kinematic regions. For K*+ and K*- mesons produced in
nu_mu CC interactions and decaying into K0 pi+/- we have found the following
yields per event: (2.6 +/- 0.2 (stat.) +/- 0.2 (syst.))% and (1.6 +/- 0.1
(stat.) +/- 0.1 (syst.))% respectively, while for the K*+ and K*- mesons
produced in nu NC interactions the corresponding yields per event are: (2.5 +/-
0.3 (stat.) +/- 0.3 (syst.))% and (1.0 +/- 0.3 (stat.) +/- 0.2 (syst.))%. The
results obtained for the rho00 parameter, 0.40 +/- 0.06 (stat) +/- 0.03 (syst)
and 0.28 +/- 0.07 (stat) +/- 0.03 (syst) for K*+ and K*- produced in nu_mu CC
interactions, are compared to theoretical predictions tuned on LEP measurements
in e+e- annihilation at the Z0 pole. For K*+ mesons produced in nu NC
interactions the measured rho00 parameter is 0.66 +/- 0.10 (stat) +/- 0.05
(syst).Comment: 20 p
Prediction of Neutrino Fluxes in the NOMAD Experiment
The method developed for the calculation of the flux and composition of the
West Area Neutrino Beam used by NOMAD in its search for neutrino oscillations
is described. The calculation is based on particle production rates computed
using a recent version of FLUKA and modified to take into account the cross
sections measured by the SPY and NA20 experiments. These particles are
propagated through the beam line taking into account the material and magnetic
fields they traverse. The neutrinos produced through their decays are tracked
to the NOMAD detector. The fluxes of the four neutrino flavours at NOMAD are
predicted with an uncertainty of about 8% for nu(mu) and nu(e), 10% for
antinu(mu), and 12% for antinu(e). The energy-dependent uncertainty achieved on
the R(e, mu) prediction needed for a nu(mu)->nu(e) oscillation search ranges
from 4% to 7%, whereas the overall normalization uncertainty on this ratio is
4.2%.Comment: 43 pages, 20 figures. Submitted to Nucl. Phys.
A study of backward going and in interactions with the NOMAD detector
Backward proton and production has been studied in
interactions with carbon nuclei. Detailed analyses of the momentum
distributions, of the production rates, and of the general features of events
with a backward going particle, have been carried out in order to understand
the mechanism producing these particles. The backward proton data have been
compared with the predictions of the reinteraction and the short range
correlation models.Comment: 29 pages, 14 figures, submitted to Nucl. Phys.
Final NOMAD results on nu_mu->nu_tau and nu_e->nu_tau oscillations including a new search for nu_tau appearance using hadronic tau decays
Results from the nu_tau appearance search in a neutrino beam using the full
NOMAD data sample are reported. A new analysis unifies all the hadronic tau
decays, significantly improving the overall sensitivity of the experiment to
oscillations. The "blind analysis" of all topologies yields no evidence for an
oscillation signal. In the two-family oscillation scenario, this sets a 90%
C.L. allowed region in the sin^2(2theta)-Delta m^2 plane which includes
sin^2(2theta)<3.3 x 10^{-4} at large Delta m^2 and Delta m^2 < 0.7 eV^2/c^4 at
sin^2(2theta)=1. The corresponding contour in the nu_e->nu_tau oscillation
hypothesis results in sin^2(2theta)<1.5 x 10^{-2} at large Delta m^2 and Delta
m^2 < 5.9 eV^2/c^4 at sin^2(2theta)=1. We also derive limits on effective
couplings of the tau lepton to nu_mu or nu_e.Comment: 46 pages, 16 figures, Latex, to appear on Nucl. Phys.
Inclusive production of and mesons in charged current interactions
The inclusive production of the meson resonances ,
and in neutrino-nucleus charged current interactions has been
studied with the NOMAD detector exposed to the wide band neutrino beam
generated by 450 GeV protons at the CERN SPS. For the first time the
meson is observed in neutrino interactions. The statistical
significance of its observation is 6 standard deviations. The presence of
in neutrino interactions is reliably established. The average
multiplicity of these three resonances is measured as a function of several
kinematic variables. The experimental results are compared to the
multiplicities obtained from a simulation based on the Lund model. In addition,
the average multiplicity of in antineutrino - nucleus
interactions is measured.Comment: 23 pages, 14 figures, 8 tables. To appear in Nucl. Phys.
A Study of Strange Particles Produced in Neutrino Neutral Current Interactions in the NOMAD Experiment
Results of a detailed study of strange particle production in neutrino
neutral current interactions are presented using the data from the NOMAD
experiment. Integral yields of neutral strange particles (K0s, Lambda,
Lambda-bar) have been measured. Decays of resonances and heavy hyperons with an
identified K0s or Lambda in the final state have been analyzed. Clear signals
corresponding to K* and Sigma(1385) have been observed. First results on the
measurements of the Lambda polarization in neutral current interactions have
been obtained.Comment: Accepted for publication in Nuclear Physics B as a rapid
communicatio
Search for nu(mu)-->nu(e) Oscillations in the NOMAD Experiment
We present the results of a search for nu(mu)-->nu(e) oscillations in the
NOMAD experiment at CERN. The experiment looked for the appearance of nu(e) in
a predominantly nu(mu) wide-band neutrino beam at the CERN SPS. No evidence for
oscillations was found. The 90% confidence limits obtained are delta m^2 < 0.4
eV^2 for maximal mixing and sin^2(2theta) < 1.4x10^{-3} for large delta m^2.
This result excludes the LSND allowed region of oscillation parameters with
delta m^2 > 10 eV^2.Comment: 19 pages, 8 figures. Submitted to Phys. Lett.
A Precise Measurement of the Muon Neutrino-Nucleon Inclusive Charged Current Cross-Section off an Isoscalar Target in the Energy Range 2.5 < E_\nu < 40 GeV by NOMAD
We present a measurement of the muon neutrino-nucleon inclusive charged
current cross-section, off an isoscalar target, in the neutrino energy range
GeV. The significance of this measurement is its
precision, % in GeV, and % in GeV regions, where significant uncertainties in previous
experiments still exist, and its importance to the current and proposed long
baseline neutrino oscillation experiments.Comment: 14 pages, 3 figures, submitted to Phys.Lett.
A Measurement of Coherent Neutral Pion Production in Neutrino Neutral Current Interactions in NOMAD
We present a study of exclusive neutral pion production in neutrino-nucleus
Neutral Current interactions using data from the NOMAD experiment at the CERN
SPS. The data correspond to muon-neutrino Charged Current
interactions in the energy range GeV. Neutrino
events with only one visible in the final state are expected to result
from two Neutral Current processes: coherent production, {\boldmath
} and single production in
neutrino-nucleon scattering. The signature of coherent production is an
emergent almost collinear with the incident neutrino while 's
produced in neutrino-nucleon deep inelastic scattering have larger transverse
momenta. In this analysis all relevant backgrounds to the coherent
production signal are measured using data themselves. Having determined the
backgrounds, and using the Rein-Sehgal model for the coherent
production to compute the detection efficiency, we obtain {\boldmath } corrected coherent- events with GeV. We measure {\boldmath }.
This is the most precise measurement of the coherent production to
date.Comment: 23 pages, 9 figures, accepted for publication in Phys. Lett.
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