The Dark Matter Search at KamLAND

Recent data from the DAMA/LIBRA phase-2 confirmed detection of a signal with independent Dark Matter (DM) annual modulation signature at a 12.9 σ CL. Our attempts to verify the DAMA/LIBRA DM observation claim led to construction of underground clean rooms at the KamLAND site and specialized laboratory for production of NaI(Tl) detectors. Current status of these facilities, methods used to grow ultra-low background NaI(Tl) crystals, and radio-purity of the latest NaI(Tl) DM detector prototype are discussed

Pulse Shape Analysis and Identification of Multipoint Events in a Large-Volume Proportional Counter in an Experimental Search for 2K Capture Kr-78

A pulse shape analysis algorithm and a method for suppressing the noise component of signals from a large copper proportional counter in the experiment aimed at searching for 2K capture of Kr-78 are described. These signals correspond to a compound event with different numbers of charge clusters due to from primary ionization is formed by these signals. A technique for separating single- and multipoint events and determining the charge in individual clusters is presented. Using the Daubechies wavelets in multiresolutional signal analysis, it is possible to increase the sensitivity and the resolution in extraction of multipoint events in the detector by a factor of 3-4.Comment: 10 pages, 8 figures. submitted to Instruments and Experimental Techniques; ISSN 0020/441

Modeling of GERDA Phase II data

The GERmanium Detector Array (Gerda) experiment at the Gran Sasso underground laboratory (LNGS) of INFN is searching for neutrinoless double-beta (0\u3bd\u3b2\u3b2) decay of 76Ge. The technological challenge of Gerda is to operate in a \u201cbackground-free\u201d regime in the region of interest (ROI) after analysis cuts for the full 100 kg\ub7yr target exposure of the experiment. A careful modeling and decomposition of the full-range energy spectrum is essential to predict the shape and composition of events in the ROI around Q\u3b2\u3b2 for the 0\u3bd\u3b2\u3b2 search, to extract a precise measurement of the half-life of the double-beta decay mode with neutrinos (2\u3bd\u3b2\u3b2) and in order to identify the location of residual impurities. The latter will permit future experiments to build strategies in order to further lower the background and achieve even better sensitivities. In this article the background decomposition prior to analysis cuts is presented for Gerda Phase II. The background model fit yields a flat spectrum in the ROI with a background index (BI) of 16.04 120.85+0.78\ub710 123 cts/(keV\ub7kg\ub7yr) for the enriched BEGe data set and 14.68 120.52+0.47\ub710 123 cts/(keV\ub7kg\ub7yr) for the enriched coaxial data set. These values are similar to the one of Phase I despite a much larger number of detectors and hence radioactive hardware components

Search for exotic physics in double-β decays with GERDA Phase II

A search for Beyond the Standard Model double-$\beta$ decay modes of$^{76}$Ge has been performed with data collected during the Phase II of theGERmanium Detector Array (GERDA) experiment, located at Laboratori Nazionalidel Gran Sasso of INFN (Italy). Improved limits on the decays involvingMajorons have been obtained, compared to previous experiments with $^{76}$Ge,with half-life values on the order of 10$^{23}$ yr. For the first time with$^{76}$Ge, limits on Lorentz invariance violation effects in double-$\beta$decay have been obtained. The isotropic coefficient$\mathring{a}_\text{of}^{(3)}$, which embeds Lorentz violation indouble-$\beta$ decay, has been constrained at the order of $10^{-6}$ GeV. Wealso set the first experimental limits on the search for light exotic fermionsin double-$\beta$ decay, including sterile neutrinos.<br

Background radioactivity of construction materials, raw substance and ready-made CaMoO4 crystals

The results of measurements of natural radioactive isotopes content in different source materials of natural and enriched composition used for CaMoO4 scintillation crystal growing are presented. The crystals are to be used in the experiment to search for neutrinoless double beta decay of 100Mo

First result of the experimental search for the 9.4 keV solar axion reactions with 83Kr in the copper proportional counter

The experimental search for solar hadronic axions is started at the Baksan Neutrino Observatory of the Institute for Nuclear Researches of Russian Academy of Science (BNO INR RAS). It is assumed that axions are created in the Sun during M1 transition between the first thermally excited level at 9.4 keV and the ground state in 83Kr. The experiment is based on axion detection via resonant absorption process by the same nucleus in the detector. The big copper proportional counter filled with krypton is used to detect signals from axions. The experimental setup is situated in the deep underground low background laboratory. No evidence of axion detection were found after the 26.5 days data collection. Resulting new upper limit on axion mass is mA ≤ 130 eV at 95% C.L. © 2015, Pleiades Publishing, Ltd101sciescopu