191 research outputs found
Longitudinal vector form factors in weak decays of nuclei
The longitudinal form factors of the weak vector current of particles with
spin and isospin are determined by the mass difference
and the charge radii of members of the isotopic doublets. The most promising
reactions to measure these form factors are the reactions with large momentum
transfers involving the spin-1/2 isotopic doublets with a maximum mass
splitting. Numerical estimates of longitudinal form factors are given for
nucleons and eight nuclear spin-1/2 isotopic doublets.Comment: 6 pages. Talk given at the 10th MEDEX'15 meeting Matrix Elements for
the Double-beta-decay Experiments, Prague, June 9-12, 201
Neutrino mass matrix in neutrino-related processes
Techniques are developed for constructing amplitudes of neutrino-related
processes in terms of the neutrino mass matrix, with no reference to the
neutrino mixing matrix. The amplitudes of neutrino oscillations in vacuum and
medium, quasi-elastic neutrino scattering, decays and double-
decays are considered. The proposed approach makes extensive use of Frobenius
covariants within the framework of Sylvester's theorem on matrix functions. The
in-medium dispersion laws are found in quadratures for three flavors of
Majorana neutrinos as an application of the developed formalism. The in-medium
dispersion laws for Dirac neutrinos can be determined in the general case by
searching for the roots of a polynomial of degree 6. In the rest frame of
baryonic matter, the minimum energy of both Majorana and Dirac neutrinos is
achieved at a finite neutrino momentum. In such cases, Dirac neutrinos occupy a
hollow Fermi sphere at zero temperature and low densities. Fitting experimental
data in terms of the neutrino mass matrix can provide better statistical
accuracy in determining the neutrino mass matrix compared to methods using the
neutrino mixing matrix at intermediate stages.Comment: 19 pages, 2 figures; accepted for publication in Physics of Atomic
Nucle
The MAJORANA 76Ge neutrino less double-beta decay project: A brief update
At present, MAJORANA is a research and development (R&D) project to
investigate the feasibility and cost of constructing and operating a one ton
decay experiment with ~1000 kg of Ge detectors fabricated from germanium
enriched to 86% in . The study will include three separate cryostats with
various types of detectors: un-segmented, un-segmented point-contact, minimally
segmented, and highly segmented. One cryostat will contain at least 30 kg of
enriched (preferably point-contact) detectors. The performance of the cryostats
and detectors as well as background levels will be investigated. The goal of
the demonstrator project is to reach a discovery sensitivity of ~ 1026 y.Comment: 3 pages, no figure
Double beta decay experiments
The present status of double beta decay experiments are reviewed. The results
of the most sensitive experiments, NEMO-3 and CUORICINO, are discussed.
Proposals for future double beta decay experiments are considered. In these
experiments sensitivity for the effective neutrino mass will be on the level of
(0.1-0.01) eV.Comment: 20 pages, 7 fugures; talk at 12-th Lomonosov Conference on Elementary
Particle Physics (Moscow, August 25-31, 2005
Interaction-enhanced nesting in Spin-Fermion and Fermi-Hubbard models
The spin-fermion (SF) model postulates that the dominant coupling between
low-energy fermions in near critical metals is mediated by collective spin
fluctuations (paramagnons) peaked at the N\'{e}el wave vector, ,
connecting hot spots on opposite sides of the Fermi surface. It has been argued
that strong correlations at hot spots lead to a Fermi surface deformation (FSD)
featuring flat regions and increased nesting. This conjecture was confirmed in
the perturbative self-consistent calculations when the paramagnon propagator
dependence on momentum deviation from is given by . Using diagrammatic Monte Carlo (diagMC) technique we show
that such a dependence holds only at temperatures orders of magnitude smaller
than any other energy scale in the problem, indicating that a different
mechanism may be at play. Instead, we find that a dependence yields a robust finite- scenario for achieving FSD. To
link phenomenological and microscopic descriptions, we applied the connected
determinant diagMC method to the Hubbard model and found that in this
case: (i) the FSD is not very pronounced, and, instead, it is the lines of
zeros of the renormalized dispersion relation that deform towards nesting; (ii)
this phenomenon appears at large before the formation of electron and
hole pockets; (iii) the static spin susceptibility is well described by
. Flat FS regions yield a non-trivial
scenario for realizing a non-Fermi liquid state.Comment: 5 pages, 4 figure
Statistical Analysis of future Neutrino Mass Experiments including Neutrino-less Double Beta Decay
We perform a statistical analysis with the prospective results of future
experiments on neutrino-less double beta decay, direct searches for neutrino
mass (KATRIN) and cosmological observations. Realistic errors are used and the
nuclear matrix element uncertainty for neutrino-less double beta decay is also
taken into account. Three benchmark scenarios are introduced, corresponding to
quasi-degenerate, inverse hierarchical neutrinos, and an intermediate case. We
investigate to what extend these scenarios can be reconstructed. Furthermore,
we check the compatibility of the scenarios with the claimed evidence of
neutrino-less double beta decay.Comment: Matches published version: Europhys.Lett.85:51002 (2009). Format
changed suitably for ArXi
New results for the two neutrino double beta decay in deformed nuclei with angular momentum projected basis
Four nuclei which are proved to be emitters (Ge,
Se, Nd, U), and four suspected, due to the corresponding
Q-values, to have this property (Nd, Sm, Gd,
Th), were treated within a proton-neutron quasiparticle random phase
approximation (pnQRPA) with a projected spherical single particle basis. The
advantage of the present procedure over the ones using a deformed Woods Saxon
or Nilsson single particle basis is that the actual pnQRPA states have a
definite angular momentum while all the others provide states having only K as
a good quantum number. The model Hamiltonian involves a mean field term
yielding the projected single particle states, a pairing interaction for alike
nucleons and a dipole-dipole proton-neutron interaction in both the
particle-hole (ph) and particle-particle (pp) channels. The effect of nuclear
deformation on the single beta strength distribution as well as on the double
beta Gamow-Teller transition amplitude (M) is analyzed. The
results are compared with the existent data and with the results from a
different approach, in terms of the process half life T. The case of
different deformations for mother and daughter nuclei is also presented.Comment: 45 pages, 13 figure
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