941 research outputs found
Thermal Model Analysis of Particle Ratios at GSI Ni-Ni Experiments Using Exact Strangeness Conservation
The production of hadrons in Ni-Ni at the GSI is considered in a hadronic gas
model with chemical equilibrium. Special attention is given to the abundance of
strange particles which are treated using the exact conservation of
strangeness. It is found that all the data can be described using a temperature
T = 70 pm 10 MeV and a baryon chemical potential mu_B = 720 pm 20 MeV.Comment: Revtex, 7 pages, 3 figures in postscript forma
Double beta decay to the excited states: experimental review
A brief review on double beta decay to excited states of daughter nuclei is
given. The ECEC(ov) transision to the excited states are discussed in
association with a possible enhancement of the decay rate by several orders of
magnitude.Comment: 5 pages; talk at MEDEX'07 ("Matrix Elements for the Double-beta-decay
Experiments"; Prague, June 11-14, 2007
Improved short-range correlations and 0nbb nuclear matrix elements of 76Ge and 82Se
We calculate the nuclear matrix elements of the neutrinoless double beta
() decays of Ge and Se for the light-neutrino
exchange mechanism. The nuclear wave functions are obtained by using realistic
two-body forces within the proton-neutron quasiparticle random-phase
approximation (pnQRPA). We include the effects that come from the finite size
of a nucleon, from the higher-order terms of nucleonic weak currents, and from
the nucleon-nucleon short-range correlations. Most importantly, we improve on
the presently available calculations by replacing the rudimentary Jastrow
short-range correlations by the more advanced unitary correlation operator
method (UCOM). The UCOM corrected matrix elements turn out to be notably larger
in magnitude than the Jastrow corrected ones. This has drastic consequences for
the detectability of decay in the present and future double
beta experiments.Comment: 5 pages, 2 figures, to appear in Physical Review C (Rapid
Communication) 200
Nuclear matrix elements of neutrinoless double beta decay with improved short-range correlations
Nuclear matrix elements of the neutrinoless double beta decays of 96Zr,
100Mo, 116Cd, 128Te, 130Te and 136Xe are calculated for the light-neutrino
exchange mechanism by using the proton-neutron quasiparticle random-phase
approximation (pnQRPA) with a realistic nucleon-nucleon force. The g_pp
parameter of the pnQRPA is fixed by the data on the two-neutrino double beta
decays and single beta decays. The finite size of a nucleon, the higher-order
terms of nucleonic weak currents, and the nucleon-nucleon short-range
correlations (s.r.c) are taken into account. The s.r.c. are computed by the
traditional Jastrow method and by the more advanced unitary correlation
operator method (UCOM). Comparison of the results obtained by the two methods
is carried out. The UCOM computed matrix elements turn out to be considerably
larger than the Jastrow computed ones. This result is important for the
assessment of the neutrino-mass sensitivity of the present and future double
beta experiments.Comment: Two figures, to be published in Physical Review C (2007) as a regular
articl
On nuclear matrix element uncertainties in short range 0vBB decay
The evaluation of short range contributions to neutrinoless double beta decay
has been challenged due to critics of the ansatz of the nuclear matrix element
calculations. We comment on the critics and uncertainties of these calculations
and the effect on the derived limits.Comment: 3 pages, Latex, new arguments adde
Double beta decay versus cosmology: Majorana CP phases and nuclear matrix elements
We discuss the relation between the absolute neutrino mass scale, the
effective mass measured in neutrinoless double beta decay, and the Majorana CP
phases. Emphasis is placed on estimating the upper bound on the nuclear matrix
element entering calculations of the double beta decay half life. Consequently,
one of the Majorana CP phases can be constrained when combining the claimed
evidence for neutrinoless double beta decay with the neutrino mass bound from
cosmology.Comment: 11 pages, 3 figure
Projected Linear Response Theory for Charge-Exchange Excitations and Double Beta Decay
The projected random phase approximation (PRPA) for charge-exchange
excitations is derived from the time-dependent variational principle. Explicit
results for the unperturbed energies (including the self-energy corrections),
the PRPA matrices, and the transition matrix elements are presented. The effect
of the projection procedure on the two-neutrino decay in
is briefly discussed.Comment: 12 pages text (LaTex) and 1 figure upon request, to be published in
Phys. Lett.
Extended shell-model calculation for even N=82 isotones with realistic effective interactions
The shell model within the shell is applied to
calculate nuclear structure properties of the even Z=52 - 62, N=82 isotones.
The results are compared with experimental data and with the results of a
quasiparticle random-phase approximation (QRPA) calculation. The interaction
used in these calculations is a realistic two-body G-matrix interaction derived
from modern meson-exchange potential models for the nucleon-nucleon
interaction. For the shell model all the two-body matrix elements are
renormalized by the -box method whereas for the QRPA the effective
interaction is defined by the G-matrix.Comment: 25 pages, Elsevier latex style. Submitted to Nuclear Physics
Nuclear moments for the neutrinoless double beta decay II
The recently developed formalism for the evaluation of nuclear form factors
in neutrinoless double beta decay is applied to , ,
, , and nuclei. Explicit analytical
expressions that follows from this theoretical development, in the single mode
model for the decay of , have been worked out. They are useful both
for testing the full numerical calculations, and for analytically checking the
consistency with other formalisms. Large configuration space calculations are
compared with previous studies, where alternative formulations were used. Yet,
besides using the G-matrix as residual interaction, we here use a simple
-force. Attention is paid to the connected effects of the short range
nuclear correlations and the finite nucleon size. Constraints on lepton number
violating terms in the weak Hamiltonian (effective neutrino Majorana mass and
effective right-handed current coupling strengths) are deduced.Comment: 18 pages, latex, minor changes, to appear in Nucl. Phys.
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