Bulletin of the American Physical Society
2006 APS April Meeting
Saturday–Tuesday, April 22–25, 2006; Dallas, TX
Session H9: Underground Neutrino Experiments and Proton Decay |
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Sponsoring Units: DNP Chair: Hamish Robertson, University of Washington Room: Hyatt Regency Dallas Cumberland B |
Sunday, April 23, 2006 8:30AM - 8:42AM |
H9.00001: Second-forbidden beta decay of ${^8}$B Minesh Bacrania, Derek Storm, R.G. Hamish Robertson The second-forbidden beta decay of ${^8}$B to the ground state of ${^8}$Be would result in the production of solar neutrinos with energies higher those currently expected. The presence of these neutrinos would be a background to a precise measurement of the ${^8}$B neutrino spectral shape, and to the detection of solar {\em hep} neutrinos. We will present an experimental limit on the branching ratio of this transition, and compare these results to a shell-model rate calculation. [Preview Abstract] |
Sunday, April 23, 2006 8:42AM - 8:54AM |
H9.00002: Periodicity studies of solar neutrino signals at the Sudbury Neutrino Observatory Aubra Anthony The Sudbury Neutrino Observatory collaboration has performed a search for sinusoidal periodicity in the $^{8}$B solar neutrino flux, and has found no evidence of variations for periods between 1 day and 10 years. I describe here an effort to use the Rayleigh Power Test to probe periodicities in the SNO data in a higher frequency range than has been previously sampled ($>$ 1 day$^{-1})$. This has the advantage of sensitivity to neutrino flux variations that might arise due to solar oscillatory activity, particularly gravitational mode oscillations (``g-mode'' oscillations), which are confined to the interior of the sun. [Preview Abstract] |
Sunday, April 23, 2006 8:54AM - 9:06AM |
H9.00003: SNO neutral current reaction detector array: sensitivity of the neutrons and alphas signal reconstuction to the electronics calibration Gersende Prior At the Sudbury Neutrino Observatory (SNO), in Ontario, Canada, an array of neutron detectors has been deployed recently to observe the neutral current reaction on deuterium. It consists of 36 $^3He-CF_4$ and 4 $^4He-CF_4$ vertical counters arranged symmetrically relative to the center of the heavy water target. With two years of data taking, enough statistics would provide an improved measurement of the total solar neutrino flux. In order to best understand data provided by this new set of detectors, electronics calibration are performed on a regular basis. Dedicated calibration campaigns were also performed to measure different electronics constants in the neutron detector electronics system. In this talk, a study of the impact of the electronics parameters on the signal reconstruction and pulse shape determination for neutrons and alphas will be presented. [Preview Abstract] |
Sunday, April 23, 2006 9:06AM - 9:18AM |
H9.00004: Measuring Cherenkov Backgrounds from Proportional Counters in SNO Stanley Seibert In the current phase of operation of the Sudbury Neutrino Observatory, He-3 proportional counters have been deployed in the center of the detector to measure neutron production from neutral-current interactions between neutrinos and deuterons in the heavy water. Radioactive decays of Bi-214 and Tl-208 in the counters produce gammas of sufficient energy to photodisintegrate deuterons, which become a background to the neutral current measurement. We have measured the background rate in-situ using Cherenkov light detected with SNO's 9456 inward-looking photomultiplier tubes. A maximum likelihood method is used to separate backgrounds in the heavy water from backgrounds in the proportional counters based upon the spatial distribution of low energy Cherenkov event vertices. Uncertainties on the backgrounds have been estimated using calibration data taken with both a distributed Na-24 source, and a contained Th source deployed at various points in the detector. [Preview Abstract] |
Sunday, April 23, 2006 9:18AM - 9:30AM |
H9.00005: Alpha Backgrounds in the SNO $^3$He Proportional Counter Array Laura Stonehill The Sudbury Neutrino Observatory (SNO) has recently deployed an array of proportional counters known as Neutral Current Detectors (NCDs) to detect thermalized neutrons via the $^3$He(n,p)$^3$H reaction. The primary physics background to the neutron-capture signal is alpha particle emission from uranium- and thorium-chain decays in the NCD walls. The expected capture rate of neutrons from the neutral-current neutrino reaction on deuterium is three per day and the intrinsic alpha background rate is approximately 250 alphas per day. Fewer than 10\% of these alphas fall into the energy range where neutron-capture signals occur, and a substantial number of these can be eliminated by pulse-shape analysis. This talk will focus on measurements of the alpha backgrounds in the NCDs and the extent to which these alphas contaminate the neutron-capture signal region. [Preview Abstract] |
Sunday, April 23, 2006 9:30AM - 9:42AM |
H9.00006: Muon Reconstruction in the Sudbury Neutrino Observatory Christopher Kyba The Sudbury Neutrino Observatory is a water Cerenkov detector located 2km under a flat rock overburden. At SNO's depth cosmic muons range out at a zenith angle of approximately 65 degrees, making it possible for SNO to measure the unoscillated atmospheric neutrino flux by observing neutrino induced muons. The approximate spherical symmetry of the detector results in a characteristic event topology for through-going muon events that depends very strongly on the muon track length but not on the direction or entrance point of the muon. An impact parameter based maximum likelihood reconstruction algorithm which incorporates both the phototube charge and time information will be discussed in this talk. The information contained in the hit pattern makes it possible to reconstruct through-going muons at very large radii, which will allow SNO to use a fiducial area which is close to the total cross sectional area of the detector. [Preview Abstract] |
Sunday, April 23, 2006 9:42AM - 9:54AM |
H9.00007: Searches for Proton Decay in Super-Kamiokande Scott Clark The results of searches for proton decay via the modes $p \to e^+ \pi^0$ and p $\to \bar{\nu} K^+$ using the Super-Kamiokande detector will be presented. These represent updates to previous searches using the same detector. [Preview Abstract] |
Sunday, April 23, 2006 9:54AM - 10:06AM |
H9.00008: Study of a highly-segmented HPGe detector at the Oroville Low-Background counting facility. Reyco Henning, David Campbell, Yuen-Dat Chan, Kevin Lesko, Michelle Perry, Alan Poon, Kai Vetter We present initial results of a study of a 8x5 segmented HPGe detector at the Oroville low radioactive background counting facility. The goal is to field a highly-segmented detector at a remote, low-background facility for an extended period of time and to evaluate its efficiency of rejecting residual radioactive backgrounds at such a facility. Applications of this study to the proposed Majorana experiment that will search for the neutrinoless double-beta decay of $^{76}$Ge will also be discussed. [Preview Abstract] |
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