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Open Access Publications from the University of California

Scholarly Works (6 results)

  • Article
  • Peer Reviewed
Recent Work (2014)
NEXT is an experiment dedicated to neutrinoless double beta decay searches in xenon. The detector is a TPC, holding 100 kg of high-pressure xenon enriched in the Xe isotope. It is under construction in the Laboratorio Subterráneo de Canfranc in Spain, and it will begin operations in 2015. The NEXT detector concept provides an energy resolutionbetter than 1% FWHM and a topological signal that can be used to reduce the background. Furthermore, the NEXT technology can be extrapolated to a 1 ton-scale experiment. © 2014 J. J. Gómez Cadenas et al. 136
    Cover page: Present status and future perspectives of the NEXT experiment
    • Article
    • Peer Reviewed
    Recent Work (2017)
    We investigate the potential of using deep learning techniques to reject background events in searches for neutrinoless double beta decay with high pressure xenon time projection chambers capable of detailed track reconstruction. The differences in the topological signatures of background and signal events can be learned by deep neural networks via training over many thousands of events. These networks can then be used to classify further events as signal or background, providing an additional background rejection factor at an acceptable loss of efficiency. The networks trained in this study performed better than previous methods developed based on the use of the same topological signatures by a factor of 1.2 to 1.6, and there is potential for further improvement.
      Cover page: Background rejection in NEXT using deep neural networks
      • Article
      • Peer Reviewed
      Recent Work (2016)
      Abstract: NEXT-100 is an electroluminescent high-pressure xenon gas time projection chamber that will search for the neutrinoless double beta (0νββ) decay of Xe. The detector possesses two features of great value for 0νββ searches: energy resolution better than 1% FWHM at the Q value of Xe and track reconstruction for the discrimination of signal and background events. This combination results in excellent sensitivity, as discussed in this paper. Material-screening measurements and a detailed Monte Carlo detector simulation predict a background rate for NEXT-100 of at most 4 × 10 counts keV kg yr . Accordingly, the detector will reach a sensitivity to the 0νββ-decay half-life of 2.8 × 10 years (90% CL) for an exposure of 100 kg·year, or 6.0 × 10 years after a run of 3 effective years.[Figure not available: see fulltext.] 136 136 −4 −1 −1 −1 25 25
        Cover page: Sensitivity of NEXT-100 to neutrinoless double beta decay
        • Article
        • Peer Reviewed
        Recent Work (2016)
        The NEXT experiment aims to observe the neutrinoless double beta decay of Xe in a high-pressure xenon gas TPC using electroluminescence (EL) to amplify the signal from ionization. One of the main advantages of this technology is the possibility to reconstruct the topology of events with energies close to Q . This paper presents the first demonstration that the topology provides extra handles to reject background events using data obtained with the NEXT-DEMO prototype. Single electrons resulting from the interactions of Na 1275 keV gammas and electronpositron pairs produced by conversions of gammas from the Th decay chain were used to represent the background and the signal in a double beta decay. These data were used to develop algorithms for the reconstruction of tracks and the identification of the energy deposited at the end-points, providing an extra background rejection factor of 24.3 ± 1.4 (stat.)%, while maintaining an efficiency of 66.7 ± 1.% for signal events.[Figure not available: see fulltext.] 136 22 228 ββ
          Cover page: First proof of topological signature in the high pressure xenon gas TPC with electroluminescence amplification for the NEXT experiment
          • Article
          • Peer Reviewed
          Recent Work (2017)
          Xe–CO mixtures are important alternatives to pure xenon in Time Projection Chambers (TPC) based on secondary scintillation (electroluminescence) signal amplification with applications in the important field of rare event detection such as directional dark matter, double electron capture and double beta decay detection. The addition of CO to pure xenon at the level of 0.05–0.1% can reduce significantly the scale of electron diffusion from 10 mm/m to 2.5 mm/m, with high impact on the discrimination efficiency of the events through pattern recognition of the topology of primary ionization trails. We have measured the electroluminescence (EL) yield of Xe–CO mixtures, with sub-percent CO concentrations. We demonstrate that the EL production is still high in these mixtures, 70% and 35% relative to that produced in pure xenon, for CO concentrations around 0.05% and 0.1%, respectively. The contribution of the statistical fluctuations in EL production to the energy resolution increases with increasing CO concentration, being smaller than the contribution of the Fano factor for concentrations below 0.1% CO . 2 2 2 2 2 2 2
            Cover page: Secondary scintillation yield of xenon with sub-percent levels of CO2 additive for rare-event detection
            • Article
            Lawrence Berkeley National Laboratory (2004)

            We present the results of a Monte-Carlo study of the sensitivity of the planned IceCube detector to predicted fluxes of muon neutrinos at TeV to PeV energies. A complete simulation of the detector and data analysis is used to study the detector's capability to search for muon neutrinos from sources such as active galaxies and gamma-ray bursts. We study the effective area and the angular resolution of the detector as a function of muon energy and angle of incidence. We present detailed calculations of the sensitivity of the detector to both diffuse and pointlike neutrino emissions, including an assessment of the sensitivity to neutrinos detected in coincidence with gamma-ray burst observations. After three years of datataking, IceCube will have been able to detect a point source flux of E2*dN/dE = 7*10^-9 cm^-2s^-1GeV at a 5-sigma significance, or, in the absence of a signal, place a 90 percent c.l. limit at a level E2*dN/dE = 2*10^-9 cm^-2s^-1GeV. A diffuse E-2 flux would be detectable at a minimum strength of E2*dN/dE = 1*10^-8 cm^-2s^-1sr^-1GeV. A gamma-ray burst model following the formulation of Waxman and Bahcall would result in a 5-sigma effect after the observation of 200 bursts in coincidence with satellite observations of the gamma-rays.

              Cover page: Sensitivity of the icecube detector to astrophysical sources of high energy muon neutrinos
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