132 research outputs found
Determination of the muon charge sign with the dipolar spectrometers of the OPERA experiment
The OPERA long-baseline neutrino-oscillation experiment has observed the
direct appearance of in the CNGS beam. Two large muon
magnetic spectrometers are used to identify muons produced in the
leptonic decay and in interactions by measuring their charge and
momentum. Besides the kinematic analysis of the decays, background
resulting from the decay of charmed particles produced in
interactions is reduced by efficiently identifying the muon track. A new method
for the charge sign determination has been applied, via a weighted angular
matching of the straight track-segments reconstructed in the different parts of
the dipole magnets. Results obtained for Monte Carlo and real data are
presented. Comparison with a method where no matching is used shows a
significant reduction of up to 40\% of the fraction of wrongly determined
charges.Comment: 10 pages. Improvements in the tex
Procedure for short-lived particle detection in the OPERA experiment and its application to charm decays
The OPERA experiment, designed to perform the first observation of oscillations in appearance mode through the detection of
the leptons produced in charged current interactions, has
collected data from 2008 to 2012. In the present paper, the procedure developed
to detect particle decays, occurring over distances of the order of 1 mm
from the neutrino interaction point, is described in detail. The results of its
application to the search for charmed hadrons are then presented as a
validation of the methods for appearance detection
Observation of nu_tau appearance in the CNGS beam with the OPERA experiment
The OPERA experiment is searching for nu_mu -> nu_tau oscillations in
appearance mode i.e. via the direct detection of tau leptons in nu_tau charged
current interactions. The evidence of nu_mu -> nu_tau appearance has been
previously reported with three nu_tau candidate events using a sub-sample of
data from the 2008-2012 runs. We report here a fourth nu_tau candidate event,
with the tau decaying into a hadron, found after adding the 2012 run events
without any muon in the final state to the data sample. Given the number of
analysed events and the low background, nu_mu -> nu_tau oscillations are
established with a significance of 4.2sigma.Comment: Submitted to Progress of Theoretical and Experimental Physics (PTEP
Limits on muon-neutrino to tau-neutrino oscillations induced by a sterile neutrino state obtained by OPERA at the CNGS beam
The OPERA experiment, exposed to the CERN to Gran Sasso beam,
collected data from 2008 to 2012. Four oscillated Charged Current
interaction candidates have been detected in appearance mode, which are
consistent with oscillations at the atmospheric within the "standard" three-neutrino framework. In this paper, the OPERA
appearance results are used to derive limits on the mixing
parameters of a massive sterile neutrino.Comment: 11 pages, 4 figures; reference to Planck result updated in the
Introduction. Submitted to JHE
Evidence for appearance in the CNGS neutrino beam with the OPERA experiment
The OPERA experiment is designed to search for oscillations in appearance mode i.e. through the direct observation
of the lepton in charged current interactions. The
experiment has taken data for five years, since 2008, with the CERN Neutrino to
Gran Sasso beam. Previously, two candidates with a decaying
into hadrons were observed in a sub-sample of data of the 2008-2011 runs. Here
we report the observation of a third candidate in the
decay channel coming from the analysis of a sub-sample of the
2012 run. Taking into account the estimated background, the absence of
oscillations is excluded at the 3.4
level.Comment: 9 pages, 5 figures, 1 table
First measurement of ν¯μ and νμ charged-current inclusive interactions on water using a nuclear emulsion detector
精密測定により素粒子ニュートリノの謎の解明を目指すNINJA実験の物理解析が開始. 京都大学プレスリリース. 2020-10-21.This paper reports the track multiplicity and kinematics of muons, charged pions, and protons from charged-current inclusive ¯νμ and νμ interactions on a water target, measured using a nuclear emulsion detector in the NINJA experiment. A 3-kg water target was exposed to the T2K antineutrino-enhanced beam corresponding to 7.1×1020 protons on target with a mean energy of 1.3 GeV. Owing to the high granularity of the nuclear emulsion, protons with momenta down to 200 MeV/c from the neutrino-water interactions were detected. We find good agreement between the observed data and model predictions for all kinematic distributions other than the number of charged pions and the muon kinematics shapes. These results demonstrate the capability of measurements with nuclear emulsion to improve neutrino interaction models
Measurement of the atmospheric muon charge ratio with the OPERA detector
The OPERA detector at the Gran Sasso underground laboratory (LNGS) was used
to measure the atmospheric muon charge ratio in the TeV energy region. We
analyzed 403069 atmospheric muons corresponding to 113.4 days of livetime
during the 2008 CNGS run. We computed separately the muon charge ratio for
single and for multiple muon events in order to select different energy regions
of the primary cosmic ray spectrum and to test the charge ratio dependence on
the primary composition. The measured charge ratio values were corrected taking
into account the charge-misidentification errors. Data have also been grouped
in five bins of the "vertical surface energy". A fit to a simplified model of
muon production in the atmosphere allowed the determination of the pion and
kaon charge ratios weighted by the cosmic ray energy spectrum.Comment: 14 pages, 10 figure
A facility to Search for Hidden Particles (SHiP) at the CERN SPS
A new general purpose fixed target facility is proposed at the CERN SPS
accelerator which is aimed at exploring the domain of hidden particles and make
measurements with tau neutrinos. Hidden particles are predicted by a large
number of models beyond the Standard Model. The high intensity of the SPS
400~GeV beam allows probing a wide variety of models containing light
long-lived exotic particles with masses below (10)~GeV/c,
including very weakly interacting low-energy SUSY states. The experimental
programme of the proposed facility is capable of being extended in the future,
e.g. to include direct searches for Dark Matter and Lepton Flavour Violation.Comment: Technical Proposa
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