299 research outputs found
Improved TPB-coated Light Guides for Liquid Argon TPC Light Detection Systems
Scintillation light produced in liquid argon (LAr) must be shifted from 128
nm to visible wavelengths in light detection systems used for liquid argon
time-projection chambers (LArTPCs). To date, LArTPC light collection systems
have employed tetraphenyl butadiene (TPB) coatings on photomultiplier tubes
(PMTs) or plates placed in front of the PMTs. Recently, a new approach using
TPB-coated light guides was proposed. In this paper, we report on light guides
with improved attenuation lengths above 100 cm when measured in air. This is an
important step in the development of meter-scale light guides for future
LArTPCs. Improvements come from using a new acrylic-based coating,
diamond-polished cast UV transmitting acrylic bars, and a hand-dipping
technique to coat the bars. We discuss a model for connecting bar response in
air to response in liquid argon and compare this to data taken in liquid argon.
The good agreement between the prediction of the model and the measured
response in liquid argon demonstrates that characterization in air is
sufficient for quality control of bar production. This model can be used in
simulations of light guides for future experiments.Comment: 25 pages, 20 figure
A Regenerable Filter for Liquid Argon Purification
A filter system for removing electronegative impurities from liquid argon is
described. The active components of the filter are adsorbing molecular sieve
and activated-copper-coated alumina granules. The system is capable of
purifying liquid argon to an oxygen-equivalent impurity concentration of better
than 30 parts per trillion, corresponding to an electron drift lifetime of at
least 10 ms. Reduction reactions that occur at about 250 degrees Celsius allow
the filter material to be regenerated in-situ through a simple procedure. In
the following work we describe the filter design, performance, and regeneration
process.Comment: 12 pages with 9 figure
Search for Differences in Oscillation Parameters for Atmospheric Neutrinos and Antineutrinos at Super-Kamiokande
We present a search for differences in the oscillations of antineutrinos and
neutrinos in the Super-Kamiokande -I, -II, and -III atmospheric neutrino
sample. Under a two-flavor disappearance model with separate mixing parameters
between neutrinos and antineutrinos, we find no evidence for a difference in
oscillation parameters. Best fit antineutrino mixing is found to be at (dm2bar,
sin2 2 thetabar) = (2.0x10^-3 eV^2, 1.0) and is consistent with the overall
Super-K measurement.Comment: 6 pages, 4 figures. Figure update
Evidence for the Appearance of Atmospheric Tau Neutrinos in Super-Kamiokande
Super-Kamiokande atmospheric neutrino data were fit with an unbinned maximum
likelihood method to search for the appearance of tau leptons resulting from
the interactions of oscillation-generated tau neutrinos in the detector.
Relative to the expectation of unity, the tau normalization is found to be
1.42 \pm 0.35 \ (stat) {\}^{+0.14}_{-0.12}\ (syst) excluding the
no-tau-appearance hypothesis, for which the normalization would be zero, at the
3.8 level. We estimate that 180.1 \pm 44.3\ (stat)
{\}^{+17.8}_{-15.2}\ (syst) tau leptons were produced in the 22.5 kton
fiducial volume of the detector by tau neutrinos during the 2806 day running
period. In future analyses, this large sample of selected tau events will allow
the study of charged current tau neutrino interaction physics with oscillation
produced tau neutrinos.Comment: 7 pages, 4 figures. This is the version as published in Physical
Review Letters including the supplemental figure. A typographical error in
the description of figure 3 is also correcte
Search for dinucleon decay into pions at Super-Kamiokande
A search for dinucleon decay into pions with the Super-Kamiokande detector
has been performed with an exposure of 282.1 kiloton-years. Dinucleon decay is
a process that violates baryon number by two units. We present the first search
for dinucleon decay to pions in a large water Cherenkov detector. The modes
O C, O
N, and O
O are investigated. No significant excess in the
Super-Kamiokande data has been found, so a lower limit on the lifetime of the
process per oxygen nucleus is determined. These limits are:
years,
years, and
years. The lower
limits on each mode are about two orders of magnitude better than previous
limits from searches for dinucleon decay in iron.Comment: 20 pages, 17 figures. Accepted for publication in Physical Review D
on March 30, 201
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