S. Seibert

Measurement of scintillation efficiency for nuclear recoils in liquid argon

The scintillation light yield of liquid argon from nuclear recoils relative to electronic recoils has been measured as a function of recoil energy from 10 keVr up to 250 keVr. The scintillation efficiency, defined as the ratio of the nuclear recoil scintillation response to the electronic recoil response, is 0.25 \pm 0.01 + 0.01(correlated) above 20 keVr.

Characterization of protonated and deuterated Tetra-Phenyl Butadiene Film in a Polystyrene Matrix

We study the effect of deuteration and annealing on the fluorescence spectrum shape and VUV to visible conversion efficiency of TPB films in a polystyrene matrix with input light from 120 to 220 nm. We observed no discernible difference in the fluorescence spectrum shape between any of the films. The deuterated film performed equally well compared to the standard one in terms of conversion efficiency, but annealing seems to degrade this efficiency to roughly 75% of its non annealed value at all wavelengths studied.

Improving Photoelectron Counting and Particle Identification in Scintillation Detectors with Bayesian Techniques

Many current and future dark matter and neutrino detectors are designed to measure scintillation light with a large array of photomultiplier tubes (PMTs). The energy resolution and particle identification capabilities of these detectors depend in part on the ability to accurately identify individual photoelectrons in PMT waveforms despite large variability in pulse amplitudes and pulse pileup. We describe a Bayesian technique that can identify the times of individual photoelectrons in a sampled PMT waveform without deconvolution, even when pileup is present. To demonstrate the technique, we apply it to the general problem of particle identification in single-phase liquid argon dark matter detectors. Using the output of the Bayesian photoelectron counting algorithm described in this paper, we construct several test statistics for rejection of backgrounds for dark matter searches in argon. Compared to simpler methods based on either observed charge or peak finding, the photoelectron counting technique improves both energy resolution and particle identification of low energy events in calibration data from the DEAP-1 detector and simulation of the larger MiniCLEAN dark matter detector.

Non-Standard Models, Solar Neutrinos, and Large \theta_{13}

Solar neutrino experiments have yet to see directly the transition region between matter-enhanced and vacuum oscillations. The transition region is particularly sensitive to models of nonstandard neutrino interactions and propagation. We examine several such nonstandard models, which predict a lower-energy transition region and a flatter survival probability for the

Nonstandard models, solar neutrinos, and large θ 13

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Characterization of the R5912-02 MOD photomultiplier tube at cryogenic temperatures

solar neutrinos than the standard large-mixing angle (LMA) model. We find that while some of the nonstandard models provide a better fit to the solar neutrino data set, the large measured value of

Nonstandard models, solar neutrinos, and largeθ13

{\ensuremath{\theta}}_{13}

Update on the MiniCLEAN Dark Matter Experiment

and the size of the experimental uncertainties lead to a low statistical significance for these fits. We have also examined whether simple changes to the solar density profile can lead to a flatter

Calibrating the Heavy Water Cherenkov Detector in Phase III of the SNO Experiment

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