Bulletin of the American Physical Society
2005 2nd Joint Meeting of the Nuclear Physics Divisions of the APS and The Physical Society of Japan
Sunday–Thursday, September 18–22, 2005; Maui, Hawaii
Session 2WF: Workshop 6B: Double Beta-Decay and Neutrino Mass |
Hide Abstracts |
Sponsoring Units: DNP JPS Chair: Kevin Lesko, Lawrence Berkeley National Laboratory Room: Ritz-Carlton Hotel Plantation 3 |
Sunday, September 18, 2005 2:00PM - 2:30PM |
2WF.00001: Neutrino properties constrained by WMAP Invited Speaker: The recent observation of the cosmic microwave background radiation by WMAP leads to precise determinination of the cosmological parameters. In this talk I will discuss how the neutrino properties such as mass are constrained by the WMAP and other observations. [Preview Abstract] |
Sunday, September 18, 2005 2:30PM - 3:00PM |
2WF.00002: Recent results from NEMO 3 experiment Invited Speaker: The main goal of the NEMO3 experiment is to study neutrinoless double beta decay of different isotopes ($^{100}$Mo, $^{82}$Se etc.) with a sensitivity of up to $\sim$ 10$^{25}$ y, which corresponds to a sensitivity for the effective Majorana neutrino mass at the level of $\sim$ (0.1 - 0.3) eV. The experiment is now going on in the Frejus underground laboratory (Laboratoire de souterrain de Modane, LSM). The recent results of this experiment are reported here. [Preview Abstract] |
Sunday, September 18, 2005 3:00PM - 3:30PM |
2WF.00003: MOON (Mo Observatory Of Neutrinos) for double beta decay Invited Speaker: MOON (Mo Observatory Of Neutrinos) is aiming to observe neutrino-less double beta decay for studying neutrino mass of 50 meV region, which is important to be explored according to recent neutrino oscillation measurements. MOON is layers of plastic scintillator which are interleaved with thin $^{100}$Mo foils. Energies of two beta-rays are measured with the plastic scintillator. A few tons of $^{100}$Mo sources are necessary to collect enough number of events. Area of the foil will be several thousands square meters. In order to put many layers of $^{100}$Mo foils, compact and simple structure is applied to MOON detector. Because of high Q-value of $^{100}$Mo double beta decay, energies of most background events are far below the Q-value. Therefore, major source of background will be coincidence of two background events. To reject such events, time resolution and position resolution will be powerful tools. Two-neutrino double beta decay is also a background event to neutrino-less double beta decay, which is related to neutrino mass. Difference of energy spectrum is only way to separate them. Therefore, good energy resolution is also required. We have developed a proto-type detector, which is named MOON-1, to investigate performances of MOON detector. MOON-1 has 5 layers of plastic scintillator plate, which size is 53 cm x 53 cm and 1 cm thick. In order to obtain good energy resolution and position sensitivity, the plates are surrounded with 32 square PMTs, which size is 6cm x 6cm, Test measurements shows that position resolution is better than 4 cm (r.m.s.). Because of good coverage of PMTs, 12{\%} (FWHM) energy resolution for 1 MeV electrons is achieved. Details of the measurements and background rejection capability are reported. [Preview Abstract] |
Sunday, September 18, 2005 3:30PM - 4:00PM |
2WF.00004: The EXO-200 detector Invited Speaker: EXO-200 is a prototype detector for the Enriched Xenon Observatory (EXO) searching for double beta decay ($\beta \beta )$ of xenon 136. It employs 200 kg of enriched liquid xenon (enriched to 80{\%} in the isotope Xe-136, already in hand for the project). The xenon, in liquid phase (LXe) is also used as active medium contained in an all-Teflon, cylindrical, time projection chamber (TPC). Currently under construction at Stanford, its functionality will be tested prior to being housed underground at WIPP, New Mexico. EXO-200 will serve as a prototype for the 1-10 ton scale EXO experiment. It will allow researching low radioactivity building materials, optimizing the performance and operation of a large-scale xenon detector, and studying some of its crucial parameters, such as energy resolution. On the other hand, once completed, it will also be the largest running double-beta decay experiment. It will not employ the Ba-136 ion tagging technique being developed for EXO. EXO-200 is designed to have very competitive sensitivity for the neutrino-less (0$\nu \beta \beta )$ process. It also aims at measuring the lifetime of the standard, although not yet observed, $\beta \beta $ decay of Xe-136 accompanied by neutrinos (2$\nu \beta \beta )$. Both the ionization signal and the scintillation light produced by ionizing events in the xenon will be recorded. Such complementary information is proven to significantly improve the energy resolution of xenon detectors, a crucial requirement in order to separate the 0$\nu \beta \beta $ and 2$\nu \beta \beta $ processes. The TPC displays an electric field parallel to the cylinder axis with a central cathode and two sets of orthogonal wires at each end for 3D position reconstruction of the events. 700 large area avalanche photodiodes collect the scintillation light. A double-walled, vacuum-insulated copper cryostat filled with fluorocarbon fluid surrounds the xenon, providing a significant buffer for external gamma radiation as well as the necessary cryogenics. [Preview Abstract] |
Sunday, September 18, 2005 4:00PM - 4:30PM |
2WF.00005: XMASS experiment and its double beta decay option Invited Speaker: XMASS is an underground experiment aimed at rare event search by using ultrapure liquid xenon in the Kamioka mine, Japan. The main physics targets of XMASS are cold dark matter, neutrinoless double beta decay, and low-energy solar neutrinos. We have done several test data taking during 2003 and 2004. We succeeded to redeuce and measure Kr radioactivity in xenon. U and Th chain radioactivities were measured by Bi-Po method and found to be very low level.\\ Although we are mainly developing dark matter detector, we have an option for double beta decay experiment with xenon. Unfortunatelly, due to high radioactivity of our PMTs, it is hard to utilize the dark matter detector for double beta decay search. We will report some activities for developing a detector for double beta decay experiment. [Preview Abstract] |
Sunday, September 18, 2005 4:30PM - 5:00PM |
2WF.00006: Double Beta Decay Options in SNO Invited Speaker: The heavy water experiment in SNO will complete data taking at the end of 2006.~ We are preparing a proposal for an experiment in which we will replace the heavy water with liquid scintillator, to measure low energy solar neutrinos, geo-neutrinos, reactor oscillations and double beta decay.~ We plan to measure double beta decay by dispersing isotopes into the scintillator volume.~ Large masses are possible, which allow us to set~effective mass limits~at a sensitivity $<$100~meV.~ I will report on the various techniques and isotopes that we~are considering. [Preview Abstract] |
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