K. Kazkaz

Comment on "Evidence for Neutrinoless Double Beta Decay"

We comment on the recent claim for the experimental observation of neutrinoless double-beta decay. We discuss several limitations in the analysis provided in that paper and conclude that there is no basis for the presented claim.

MaGe-a Geant4-Based Monte Carlo Application Framework for Low-Background Germanium Experiments

We describe a physics simulation software framework, MaGe, that is based on the Geant4 simulation toolkit. MaGe is used to simulate the response of ultra-low radioactive background detectors to ionizing radiation, specifically the Majorana and Gerda neutrinoless double-beta decay experiments. Majorana and Gerda use high-purity germanium detectors to search for the neutrinoless double-beta decay of 76Ge and MaGe is jointly developed between these two collaborations. The MaGe framework contains the geometry models of common objects, prototypes, test stands and the actual experiments. It also implements customized event generators, Geant4 physics lists and output formats. All of these features are available as class libraries that are typically compiled into a single executable. The user selects the particular experimental setup implementation at run-time via macros. The combination of all these common classes into one framework reduces duplication of efforts, eases comparison between simulated data and experiment and simplifies the addition of new detectors to be simulated. This paper focuses on the software framework, custom event generators and physics lists.

Pulse shape analysis in segmented detectors as a technique for background reduction in Ge double-beta decay experiments

The need to understand and reject backgrounds in Ge-diode detector double-beta decay experiments has given rise to the development of pulse shape analysis in such detectors to discern single-site energy deposits from multiple-site deposits. Here, we extend this analysis to segmented Ge detectors to study the effectiveness of combining segmentation with pulse shape analysis to identify the multiplicity of the energy deposits.

The Majorana neutrinoless double-beta decay experiment

The proposed Majorana double-beta decay experiment is based on an array of segmented intrinsic Ge detectors with a total mass of 500 kg of Ge isotopically enriched to 86% in 76Ge. A discussion is given of background reduction by material selection, detector segmentation, pulse shape analysis, and electroformation of copper parts and granularity. Predictions of the experimental sensitivity are given. For an experimental running time of 10 years over the construction and operation oft he Majorana setup, a sensitivity of T1/20ν∼4×1027 yr is predicted. This corresponds to 〈mν〉∼0.003−0.004 eV according to recent QRPA and RQRPA matrix element calculations.

Neutron inelastic scattering processes as a background for double-{beta} decay experiments

We investigate several Pb(n,n{sup }{gamma}) and Ge(n,n{sup }{gamma}) reactions. We measure {gamma}-ray production from Pb(n,n{sup }{gamma}) reactions that can be a significant background for double-{beta} decay experiments which use lead as a massive inner shield. Particularly worrisome for Ge-based double-{beta} decay experiments are the 2041-keV and 3062-keV {gamma} rays produced via Pb(n,n{sup }{gamma}). The former is very close to the {sup 76}Ge double-{beta} decay endpoint energy and the latter has a double escape peak energy near the endpoint. We discuss the implications of these {gamma} rays on past and future double-{beta} decay experiments and estimate the cross section to excite the level that produces the 3062-keV {gamma} ray. Excitation {gamma}-ray lines from Ge(n,n{sup }{gamma}) reactions are also observed. We consider the contribution of such backgrounds and their impact on the sensitivity of next-generation searches for neutrinoless double-{beta} decay using enriched germanium detectors.

MEGA: a low-background radiation detector

The Multiple-Element Gamma Assay (MEGA) is a low-background detector designed to support environmental monitoring and national security applications. MEGA also demonstrates technology needed for Majorana, a next generation neutrino mass experiment. It will employ active and passive shielding to reduce backgrounds. It will also exploit multi-coincidence signatures to identify specific radioactive isotopes. MEGA is expected to begin operation in late 2003 at the Waste Isolation Pilot Plant in Carlsbad, NM.

Depth‐Sensitivity Relation (DSR) for Underground Laboratories

Muon‐induced background can limit the sensitivity of next generation experiments searching for neutrinoless double beta decay and WIMP dark matter. We have established the DSR based upon the muon and muon‐induced fast neutron fluxes and spectra for a number of underground laboratories. Our results indicate that the muon‐induced neutron elastic and inelastic scattering processes create a significant background for germanium‐based dark matter and double beta decay experiments, unless such experiments are staged deep underground. We use the measured neutron elastic and inelastic scattering processes with a segmented CLOVER (germanium) detector on the surface to test our model predictions.

The Majorana Zero-Neutrino Double-Beta Decay Experiment White Paper

The Majorana Collaboration: Brown University, Providence, RI Institute for Theoretical and Experimental Physics, Moscow, Russia Joint Institute for Nuclear Research, Dubna, Russia Lawrence Berkeley National Laboratory, Berkeley, CA Lawrence Livermore National Laboratory, Livermore, CA Los Alamos National Laboratory, Los Alamos, NM New Mexico State University, Carlsbad, NM Oak Ridge National Laboratory, Oak Ridge, TN Osaka University, Osaka, Japan Pacific Northwest National Laboratory, Richland, WA Queen’s University, Kingston, Canada Triangle Universities Nuclear Laboratory, Durham, NC University of Chicago, Chicago, IL University of South Carolina, Columbia, SC University of Tennessee, Knoxville, TN University of Washington, Seattle, WA