![]() ![]() The thickness of the SXe layer is monitored by interference fringes in the reflected light guided by a second fiber.īa atom/ion fluorescence is collected by an efficient lens and focused on a CCD chip in the probe to produce an image of the single atom/ion. The light is deflected to illuminate the region of SXe where the Ba atom/ion is trapped. The laser light needed to excite the single Ba + or Ba enters via an optical fiber within the probe. This traps the Ba + ion (or Ba atom) in a thin layer of SXe on the sapphire window at the end of the probe. When the probe is near the 136Ba + daughter ion, the flow of cooling gas, e.g., high pressure argon gas expanding through a Joule-Thompson nozzle or cryogenic helium gas, is increased to cool the end of the vacuum-insulated probe to below the Xe freezing point of 161 K. However, our efforts to demonstrate direct barium tagging in liquid xenon with lasers have thus far been inconclusive Hall ( 2012).Ī concept for such a barium tagging probe is shown on the right in Fig. ![]() The original barium tagging proposal Moe ( 1991) called for exciting and detecting the 136Ba ion by lasers directed through the liquid xenon to the decay site. The one exception, background from the two-neutrino double beta decays, is estimated to be negligible still for multi-ton detectors and observed energy resolutions. With this additional identification, or “tag”, all backgrounds of a 136Xe 0 ν β β decay experiment in the energy range of interest near the Q value could be vetoed. In liquid xenon (LXe), it has been proposed that after single charge transfer in the liquid, the daughter 136Ba + ion might be identified i n s i t u by laser spectroscopy at the site of the decay. The 0 ν β β decay of 136Xe produces a daughter ion 136Ba + + ( 136Xe → 136Ba + + + 2 e −). In next generation experiments at the ton scale, complete elimination of background would be a great advantage, as the sensitivity to lifetime grows linearly with the mass of the isotope in the detector, M, in the zero background case, whereas the sensitivity grows as M 1 / 2 with backgrounds that increase proportionately with mass.Īmong all the double beta decay isotopes, 136Xe is unique because the decay medium can be a transparent liquid or gas. The most sensitive 0 ν β β decay experiments to date, with tens to hundreds of kilograms of the isotope of interest, have reached 0 ν β β decay lifetime limits of greater than 10 25 years Auger et al. Successful observation of 0 ν β β decay would determine the fundamental character of neutrinos to be Majorana rather than Dirac, and could provide the additional information needed to infer the absolute masses of the neutrinos Avignone III et al. Institute for Theoretical and Experimental Physics, Moscow, Russiaĭepartment of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook NY,USAĭepartment of Physics, University of Seoul, Seoul, Koreaĭepartment of Physics, University of South Dakota, Vermillion SD, USAĪ novel application of matrix isolation spectroscopy is being explored by the nEXO collaboration for a future ton-scale 136Xe neutrinoless double beta decay ( 0 ν β β) experiment. Physics Department, University of Massachusetts, Amherst MA, USA Lawrence Livermore National Laboratory, Livermore CA, USA LHEP, Albert Einstein Center, University of Bern, Bern, Switzerland Technische Universitat Munchen, Physikdepartment and Excellence Cluster Universe, Garching, Germany Oak Ridge National Laboratory, Oak Ridge TN, USA Institute of High Energy Physics, Beijing, Chinaĭepartment of Physics, Drexel University, Philadelphia PA, USA Physics Department, Stanford University, Stanford CA, USA SLAC National Accelerator Laboratory, Stanford CA, USA Physics Department, University of Illinois, Urbana-Champaign IL, USA Physics Department, Carleton University, Ottawa ON, Canada ![]() Physics Department and CEEM, Indiana University, Bloomington IN, USAĭepartment of Physics and Astronomy, University of Alabama, Tuscaloosa AL, USAĭepartment of Physics, Duke University, and Triangle Universities Nuclear Laboratory (TUNL), Durham North Carolina, USA Physics Department, Colorado State University, Fort Collins CO, USAĭepartment of Physics, Laurentian University, Sudbury ON, Canada ![]()
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