299 research outputs found
Review of double beta experiments
This paper is the first part of the manuscript written in April 2012 for my
academic Accreditation to supervise research. It offers a review of the double
beta experimental techniques. My purpose is to detail, for each technique, the
different origins of background, how they can be identified, and how they can
be reduced. Advantages and limitations are discussed. This review is organized
as follows. First, the question of the possible Majorana nature for the
neutrino is presented and the physic of neutrinoless double beta decay is
summarized. Then I begin by presenting the tracko-calo NEMO-3 and SuperNEMO
experiments. I've worked on these two experiments since 15 years. So it was
natural to start with them with a relatively more exhaustive description. I
will then present the germanium technique. I will then review the bolometer
technique. I will describe in detail the recent progress in scintillating
bolometers because I think that it is one of the most promising techniques.
Finally I will review the large liquid scintillator detectors and Xenon TPC.
The last chapter offers a summary of the different techniques and projects.Comment: 100 pages; Manuscript for Accreditation to supervise research (Univ.
Paris-Sud 11), May 201
Double Beta Decay, Majorana Neutrinos, and Neutrino Mass
The theoretical and experimental issues relevant to neutrinoless double-beta
decay are reviewed. The impact that a direct observation of this exotic process
would have on elementary particle physics, nuclear physics, astrophysics and
cosmology is profound. Now that neutrinos are known to have mass and
experiments are becoming more sensitive, even the non-observation of
neutrinoless double-beta decay will be useful. If the process is actually
observed, we will immediately learn much about the neutrino. The status and
discovery potential of proposed experiments are reviewed in this context, with
significant emphasis on proposals favored by recent panel reviews. The
importance of and challenges in the calculation of nuclear matrix elements that
govern the decay are considered in detail. The increasing sensitivity of
experiments and improvements in nuclear theory make the future exciting for
this field at the interface of nuclear and particle physics.Comment: invited submission to Reviews of Modern Physics, higher resolution
figures available upon request from authors, Version 2 has fixed typos and
some changes after referee report
Challenges in Double Beta Decay
After nearly 80 years since the first guess on its existence, neutrino still
escapes our insight: the mass and the true nature (Majorana or Dirac) of this
particle is still unknown. In the past ten years, neutrino oscillation
experiments have finally provided the incontrovertible evidence that neutrinos
mix and have finite masses. These results represent the strongest demonstration
that the Standard Model of electroweak interactions is incomplete and that new
Physics beyond it must exist. None of these experimental efforts could however
shade light on some of the basic features of neutrinos. Indeed, absolute scale
and ordering of the masses of the three generations as well as charge
conjugation and lepton number conservation properties are still unknown. In
this scenario, a unique role is played by the Neutrinoless Double Beta Decay
searches: these experiments can probe lepton number conservation, investigate
the Dirac/Majorana nature of the neutrinos and their absolute mass scale
(hierarchy problem) with unprecedented sensitivity. Today Neutrinoless Double
Beta Decay faces a new era where large scale experiments with a sensitivity
approaching the so-called degenerate-hierarchy region are nearly ready to start
and where the challenge for the next future is the construction of detectors
characterized by a tonne-scale size and an incredibly low background, to fully
probe the inverted-hierarchy region. A number of new proposed projects took up
this challenge. These are based either on large expansions of the present
experiments or on new ideas to improve the technical performance and/or reduce
the background contributions. n this paper, a review of the most relevant
ongoing experiments is given. The most relevant parameters contributing to the
experimental sensitivity are discussed and a critical comparison of the future
projects is proposed.Comment: 70 pages, 16 figures, 6 tables. arXiv admin note: text overlap with
arXiv:1109.5515, arXiv:hep-ex/0501010, arXiv:0910.2994 by other author
Inelastic Neutron Scattering Studies of \u3csup\u3e76\u3c/sup\u3eGe and \u3csup\u3e76\u3c/sup\u3eSe: Relevance to Elevance to Neutrinoless Double-β Decay
Inelastic neutron scattering measurements were performed at the University of Kentucky Accelerator Laboratory on enriched 76Ge and 76Se scattering samples. From measurements at incident neutron energies from 2.0 to 4.0 MeV, many new levels were identified and characterized in each nucleus; level lifetimes, transition probabilities, multipole mixing ratios, and other properties were determined. In addition, γ-ray cross sections for the 76Ge(n,n′γ) reaction were measured at neutron energies up to 5.0 MeV, with the goal of determining the cross sections of γ rays in 2040-keV region, which corresponds to the region of interest in the neutrinoless double β decay of 76Ge. Gamma rays from the three strongest branches from the 3952-keV level were observed, but the previously reported 2041-keV γ ray was not. Population cross sections across the range of incident neutron energies were determined for the 3952-keV level, resulting in a cross section of ~0.1 mb for the 2041-keV branch using the previously determined branching ratios. Beyond this, the data from these experiments indicate that previously unreported γ rays from levels in 76Ge can be found in the 2039-keV region
Probing particle and nuclear physics models of neutrinoless double beta decay with different nuclei
Half-life estimates for neutrinoless double beta decay depend on particle
physics models for lepton flavor violation, as well as on nuclear physics
models for the structure and transitions of candidate nuclei. Different models
considered in the literature can be contrasted - via prospective data - with a
"standard" scenario characterized by light Majorana neutrino exchange and by
the quasiparticle random phase approximation, for which the theoretical
covariance matrix has been recently estimated. We show that, assuming future
half-life data in four promising nuclei (Ge-76, Se-82, Te-130, and Xe-136), the
standard scenario can be distinguished from a few nonstandard physics models,
while being compatible with alternative state-of-the-art nuclear calculations
(at 95% C.L.). Future signals in different nuclei may thus help to discriminate
at least some decay mechanisms, without being spoiled by current nuclear
uncertainties. Prospects for possible improvements are also discussed.Comment: Minor corrections in the text, references added. Matches published
version in Phys. Rev. D 80, 015024 (2009
Neutrino-less Double Beta Decay and Particle Physics
We review the particle physics aspects of neutrino-less double beta decay.
This process can be mediated by light massive Majorana neutrinos (standard
interpretation) or by something else (non-standard interpretations). The
physics potential of both interpretations is summarized and the consequences of
future measurements or improved limits on the half-life of neutrino-less double
beta decay are discussed. We try to cover all proposed alternative realizations
of the decay, including light sterile neutrinos, supersymmetric or left-right
symmetric theories, Majorons, and other exotic possibilities. Ways to
distinguish the mechanisms from one another are discussed. Experimental and
nuclear physics aspects are also briefly touched, alternative processes to
double beta decay are discussed, and an extensive list of references is
provided.Comment: 96 pages, 38 figures. Published versio
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