302 research outputs found
Automatic track recognition for large-angle minimum ionizing particles in nuclear emulsions
We previously developed an automatic track scanning system which enables the
detection of large-angle nuclear fragments in the nuclear emulsion films of the
OPERA experiment. As a next step, we have investigated this system's track
recognition capability for large-angle minimum ionizing particles . This paper shows that, for such tracks, the system has
a detection efficiency of 95 or higher and reports the achieved angular
accuracy of the automatically recognized tracks. This technology is of general
purpose and will likely contribute not only to various analyses in the OPERA
experiment, but also to future experiments, e.g. on low-energy neutrino and
hadron interactions, or to future research on cosmic rays using nuclear
emulsions carried by balloons.Comment: 11 pages, 10 figures, accepted by JINS
A Hybrid 3D/2D Field Response Calculation for Liquid Argon Detectors with PCB Based Anode Plane
Liquid Argon Time Projection Chamber (LArTPC) technology is commonly utilized
in neutrino detector designs. It enables detailed reconstruction of neutrino
events with high spatial precision and low energy threshold. Its field response
(FR) model describes the time-dependent electric currents induced in the
anode-plane electrodes when ionization electrons drift nearby. An accurate and
precise FR is a crucial input to LArTPC detector simulations and charge
reconstruction. Established LArTPC designs have been based on parallel wire
planes. It allows accurate and computationally economic two-dimensional (2D) FR
models utilizing the translational symmetry along the direction of the wires.
Recently, novel LArTPC designs utilize electrodes formed on printed circuit
board (PCB) in the shape of strips with through holes. The translational
symmetry is no longer a good approximation near the electrodes and a new FR
calculation that employs regions with three dimensions (3D) has been developed.
Extending the 2D models to 3D would be computationally expensive. Fortuitously,
the nature of strips with through holes allows for a computationally economic
approach based on the finite-difference method (FDM). In this paper, we present
a new software package "pochoir" that calculates LArTPC field response for
these new strip-based anode designs. This package combines 3D calculations in
the volume near the electrodes with 2D far-field solutions to achieve fast and
precise field response computation. We apply the resulting FR to simulate and
reconstruct samples of cosmic-ray muons and Ar decays from a Vertical
Drift (VD) detector prototype operated at CERN. We find the difference between
real and simulated data within 5 %. Current state-of-the-art LArTPC software
requires a 2D FR which we provide by averaging over one dimension and estimate
that variations lost in this average are smaller than 7 %.Comment: 16 pages, 12 figure
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
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
Emulsion sheet doublets as interface trackers for the OPERA experiment
New methods for efficient and unambiguous interconnection between electronic
counters and target units based on nuclear photographic emulsion films have
been developed. The application to the OPERA experiment, that aims at detecting
oscillations between mu neutrino and tau neutrino in the CNGS neutrino beam, is
reported in this paper. In order to reduce background due to latent tracks
collected before installation in the detector, on-site large-scale treatments
of the emulsions ("refreshing") have been applied. Changeable Sheet (CSd)
packages, each made of a doublet of emulsion films, have been designed,
assembled and coupled to the OPERA target units ("ECC bricks"). A device has
been built to print X-ray spots for accurate interconnection both within the
CSd and between the CSd and the related ECC brick. Sample emulsion films have
been extensively scanned with state-of-the-art automated optical microscopes.
Efficient track-matching and powerful background rejection have been achieved
in tests with electronically tagged penetrating muons. Further improvement of
in-doublet film alignment was obtained by matching the pattern of low-energy
electron tracks. The commissioning of the overall OPERA alignment procedure is
in progress.Comment: 19 pages, 19 figure
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
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
Design and construction of the MicroBooNE Cosmic Ray Tagger system
The MicroBooNE detector utilizes a liquid argon time projection chamber
(LArTPC) with an 85 t active mass to study neutrino interactions along the
Booster Neutrino Beam (BNB) at Fermilab. With a deployment location near ground
level, the detector records many cosmic muon tracks in each beam-related
detector trigger that can be misidentified as signals of interest. To reduce
these cosmogenic backgrounds, we have designed and constructed a TPC-external
Cosmic Ray Tagger (CRT). This sub-system was developed by the Laboratory for
High Energy Physics (LHEP), Albert Einstein center for fundamental physics,
University of Bern. The system utilizes plastic scintillation modules to
provide precise time and position information for TPC-traversing particles.
Successful matching of TPC tracks and CRT data will allow us to reduce
cosmogenic background and better characterize the light collection system and
LArTPC data using cosmic muons. In this paper we describe the design and
installation of the MicroBooNE CRT system and provide an overview of a series
of tests done to verify the proper operation of the system and its components
during installation, commissioning, and physics data-taking
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