Measurement of double beta decay of 100Mo to excited states in the NEMO 3 experiment

The double beta decay of 100Mo to the 0^+_1 and 2^+_1 excited states of 100Ru is studied using the NEMO 3 data. After the analysis of 8024 h of data the half-life for the two-neutrino double beta decay of 100Mo to the excited 0^+_1 state is measured to be T^(2nu)_1/2 = [5.7^{+1.3}_{-0.9}(stat)+/-0.8(syst)]x 10^20 y. The signal-to-background ratio is equal to 3. Information about energy and angular distributions of emitted electrons is also obtained. No evidence for neutrinoless double beta decay to the excited 0^+_1 state has been found. The corresponding half-life limit is T^(0nu)_1/2(0^+ --> 0^+_1) > 8.9 x 10^22 y (at 90% C.L.). The search for the double beta decay to the 2^+_1 excited state has allowed the determination of limits on the half-life for the two neutrino mode T^(2nu)_1/2(0^+ --> 2^+_1) > 1.1 x 10^21 y (at 90% C.L.) and for the neutrinoless mode T^(0nu)_1/2(0^+ --> 2^+_1) > 1.6 x 10^23 y (at 90% C.L.).Comment: 23 pages, 7 figures, 4 tables, submitted to Nucl. Phy

Results of the BiPo-1 prototype for radiopurity measurements for the SuperNEMO double beta decay source foils

The development of BiPo detectors is dedicated to the measurement of extremely high radiopurity in $^{208}$Tl and $^{214}$Bi for the SuperNEMO double beta decay source foils. A modular prototype, called BiPo-1, with 0.8 $m^2$ of sensitive surface area, has been running in the Modane Underground Laboratory since February, 2008. The goal of BiPo-1 is to measure the different components of the background and in particular the surface radiopurity of the plastic scintillators that make up the detector. The first phase of data collection has been dedicated to the measurement of the radiopurity in $^{208}$Tl. After more than one year of background measurement, a surface activity of the scintillators of $\mathcal{A}$($^{208}$Tl) $=$ 1.5 $\mu$Bq/m$^2$ is reported here. Given this level of background, a larger BiPo detector having 12 m$^2$ of active surface area, is able to qualify the radiopurity of the SuperNEMO selenium double beta decay foils with the required sensitivity of $\mathcal{A}$($^{208}$Tl) $<$ 2 $\mu$Bq/kg (90% C.L.) with a six month measurement.Comment: 24 pages, submitted to N.I.M.

Precision Measurement of the Proton Flux in Primary Cosmic Rays from Rigidity 1 GV to 1.8 TV with the Alpha Magnetic Spectrometer on the International Space Station

A precise measurement of the proton flux in primary cosmic rays with rigidity (momentum/charge) from 1 GV to 1.8 TV is presented based on 300 million events. Knowledge of the rigidity dependence of the proton flux is important in understanding the origin, acceleration, and propagation of cosmic rays. We present the detailed variation with rigidity of the flux spectral index for the first time. The spectral index progressively hardens at high rigidities.</p

Highly-parallelized simulation of a pixelated LArTPC on a GPU

The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on 10^3 pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype

Energy resolution of plastic scintillation counters for beta rays

Recent experiments of neutrino-less double beta decays have been developing for studying the effective mass of neutrinos. Some of them use plastic scintillator for detecting the beta ray energy. Good energy resolution is a key for the neutrino- less double beta decay experiments (MOON, superNEMO, etc.). The motivation in this work is to study the energy resolution of a plastic scintillation counter in terms of "components" in the MeV-electron region. It is known that total energy resolution of a scintillation counter for a mono-energetic spectrum is separated into two components (statistical and non-statistical components). This paper presents for studying these two components on a plastic scintillation counter for electrons. Experiments on protons are also performed to compare to electron data. Experimental results point out that the statistical component is inversely proportional to the square root of the number of photo-electrons. In the case of electrons, data set of the non-statistical component described as approximately inversely proportional to the square root of electron energies. Three additional experiments are needed to carry out, (such as measuring (1) the uniformity of the plastic scintillator materials, BC-408, by scanning a 2.8-MeV proton micro-beam, (2) the energy spread of electrons and protons, and (3) the effect of electron-beam size on the set-up), to be sure that they do not affect measuring these two components. This present work is useful for investigating as well as improving the energy resolution of a plastic scintillation counter through statistical and non-statistical components

Energy resolution of plastic scintillation detector for beta rays

Many experiments on neutrinoless double beta decays have been proposed recently for determining the effective mass of neutrinos. Some of them use a plastic scintillation for measuring the beta-ray energy. Achieving a high energy resolution is critical for neutrinoless double beta decay experiments (e.g., MOON and superNEMO). The motivation of this study is to investigate the energy resolution of a plastic scintillation detector in terms of ldquocomponentsrdquo in the MeV-electron region. It is known that the total energy resolution of a plastic scintillation detector for a monoenergetic spectrum consists of two components: statistical and intrinsic energy resolution. In this paper, these two components were investigated for electrons. Experiments on protons were also performed for the purpose of comparison. Three additional experiments were performed to determine (1) the uniformity of the plastic scintillator materials by scanning a 2.8-MeV proton microbeam, (2) the energy spread of electrons and protons, and (3) the effect of the electron-beam size on the set-up. These additional experiments were performed to ensure that these factors did not affect measurements of the two above-mentioned components

Large Synoptic Survey Telescope: Dark Energy Science Collaboration

See paper for full list of authors - 133 pages; a White Paper describing the goals of the LSST Dark Energy Science Collaboration and its work plan for the next three yearsThis white paper describes the LSST Dark Energy Science Collaboration (DESC), whose goal is the study of dark energy and related topics in fundamental physics with data from the Large Synoptic Survey Telescope (LSST). It provides an overview of dark energy science and describes the current and anticipated state of the field. It makes the case for the DESC by laying out a robust analytical framework for dark energy science that has been defined by its members and the comprehensive three-year work plan they have developed for implementing that framework. The analysis working groups cover five key probes of dark energy: weak lensing, large scale structure, galaxy clusters, Type Ia supernovae, and strong lensing. The computing working groups span cosmological simulations, galaxy catalogs, photon simulations and a systematic software and computational framework for LSST dark energy data analysis. The technical working groups make the connection between dark energy science and the LSST system. The working groups have close linkages, especially through the use of the photon simulations to study the impact of instrument design and survey strategy on analysis methodology and cosmological parameter estimation. The white paper describes several high priority tasks identified by each of the 16 working groups. Over the next three years these tasks will help prepare for LSST analysis, make synergistic connections with ongoing cosmological surveys and provide the dark energy community with state of the art analysis tools. Members of the community are invited to join the LSST DESC, according to the membership policies described in the white paper. Applications to sign up for associate membership may be made by submitting the Web form at http://www.slac.stanford.edu/exp/lsst/desc/signup.html with a short statement of the work they wish to pursue that is relevant to the LSST DESC