218 research outputs found
Anode-Coupled Readout for Light Collection in Liquid Argon TPCs
This paper will discuss a new method of signal read-out from photon detectors
in ultra-large, underground liquid argon time projection chambers. In this
design, the signal from the light collection system is coupled via capacitive
plates to the TPC wire-planes. This signal is then read out using the same
cabling and electronics as the charge information. This greatly benefits light
collection: it eliminates the need for an independent readout, substantially
reducing cost; It reduces the number of cables in the vapor region of the TPC
that can produce impurities; And it cuts down on the number of feed-throughs in
the cryostat wall that can cause heat-leaks and potential points of failure. We
present experimental results that demonstrate the sensitivity of a LArTPC wire
plane to photon detector signals. We also simulate the effect of a 1 s
shaping time and a 2 MHz sampling rate on these signals in the presence of
noise, and find that a single photoelectron timing resolution of 30 ns
can be achieved.Comment: 16 pages, 15 figure
Demonstration of a Lightguide Detector for Liquid Argon TPCs
We report demonstration of light detection in liquid argon using an acrylic
lightguide detector system. This opens the opportunity for development of an
inexpensive, large-area light collection system for large liquid argon time
projection chambers. The guides are constructed of acrylic, with TPB embedded
in a surface coating with a matching index of refraction. We study the response
to early scintillation light produced by a 5.3 MeV alpha. We measure coating
responses from 7 to 8 PE on average, compared to an ideal expectation of 10 PE
on average. We estimate the attenuation length of light along the lightguide
bar to be greater than 0.5 m. The coating response and the attenuation length
can be improved; we show, however, that these results are already sufficient
for triggering in a large detector
Environmental Effects on TPB Wavelength-Shifting Coatings
The scintillation detection systems of liquid argon time projection chambers
(LArTPCs) require wavelength shifters to detect the 128 nm scintillation light
produced in liquid argon. Tetraphenyl butadiene (TPB) is a fluorescent material
that can shift this light to a wavelength of 425 nm, lending itself well to use
in these detectors. We can coat the glass of photomultiplier tubes (PMTs) with
TPB or place TPB-coated plates in front of the PMTs.
In this paper, we investigate the degradation of a chemical TPB coating in a
laboratory or factory environment to assess the viability of long-term TPB film
storage prior to its initial installation in an LArTPC. We present evidence for
severe degradation due to common fluorescent lights and ambient sunlight in
laboratories, with potential losses at the 40% level in the first day and
eventual losses at the 80% level after a month of exposure. We determine the
degradation is due to wavelengths in the UV spectrum, and we demonstrate
mitigating methods for retrofitting lab and factory environments
On two weak CC Delta production models
We perform a detail analysis of two models of neutrino CC Delta production on
free nucleons. First model is a standard one based on nucleon-Delta transition
current with several form-factors. Second model is a starting point for a
construction of Marteau model with sophisticated analytical computations of
nuclear effects. We conclude that both models lead to similar results.Comment: 9 pages, includes 9 figures, accepted for publication in J. Phys.
New Measurements of Nucleon Structure Functions from the CCFR/NuTeV Collaboration
We report on the extraction of the structure functions F_2 and Delta xF_3 =
xF_3nu-xF_3nubar from CCFR neutrino-Fe and antineutrino-Fe differential cross
sections. The extraction is performed in a physics model independent (PMI) way.
This first measurement for Delta xF_3, which is useful in testing models of
heavy charm production, is higher than current theoretical predictions. The F_2
(PMI) values measured in neutrino and muon scattering are in good agreement
with the predictions of Next to Leading Order PDFs (using massive charm
production schemes), thus resolving the long-standing discrepancy between the
two sets of data.Comment: 5 pages. Presented by Arie Bodek at the CIPNAP2000 Conference, Quebec
City, May 200
A Precise Determination of Electroweak Parameters in Neutrino-Nucleon Scattering
The NuTeV collaboration has extracted sin^2theta_W from the ratios of neutral
current to charged current neutrino and anti-neutrino cross-sections. Our
value, sin^2theta_W(on-shell)=0.2277+/-0.0013(stat)+/-0.0009(syst), is three
standard deviations above the standard model prediction. We also present a
model independent analysis of the same data.Comment: ReVTeX, 5 pp, 1fig; v2. revised SM prediction; v3. more sig. digits
in Eqns 6-7, fix error in Eqn
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