1,253 research outputs found
Neutrinoless double beta decay with scalar bilinears
One possible probe to physics beyond the standard model is to look for scalar
bilinears, which couple to two fermions of the standard model. We point out
that the scalar bilinears allow new diagrams contributing to the neutrinoless
double beta decay. The upper bound on the neutrinoless double beta decay
lifetime would then give new constraints on the ratio of the masses of these
scalars to their couplings to the fermions.Comment: 11 pages latex with 3 figure
Confronting Dilaton-exchange gravity with experiments
We study the experimental constraints on theories, where the equivalence
principle is violated by dilaton-exchange contributions to the usual
graviton-exchange gravity. We point out that in this case it is not possible to
have any CPT violation and hence there is no constraint from the CPT violating
measurements in the system. The most stringent bound is obtained from the
mass difference. In contrast, neither neutrino oscillation
experiments nor neutrinoless double beta decay imply significant constraints.Comment: 7 page
Microscopic Calculations of Weak Interaction Rates of Nuclei in Stellar Environment for A = 18 to 100
We report here the microscopic calculation of weak interaction rates in
stellar matter for 709 nuclei with A = 18 to 100 using a generalized form of
proton-neutron quasiparticle RPA model with separable Gamow-Teller forces. This
is the first ever extensive microscopic calculation of weak rates calculated
over a wide temperature-density grid which includes 10^7 \leq T(K) \leq 30
\times 10^9 and 10 \leq \rho Y_{e} (gcm^{-3}) \leq 10^{11}, and over a larger
mass range. Particle emission processes from excited states, previously
ignored, are taken into account, and are found to significantly affect some
decay rates. The calculated capture and decay rates take into
consideration the latest experimental energy levels and value
compilations. Our calculation of electron capture and -decay rates, in
the -shell, show considerable differences with a recently reported shell
model diagonalization approach calculation.Comment: 9 page
Effects of New Gravitational Interactions on Neutrinoless Double Beta Decay
It has recently been proposed that violations of Lorentz invariance or
violations of the equivalence principle can be constrained from the
non-observation of neutrinoless double beta decay. We generalize this analysis
to all possible new gravitational interactions and discuss briefly the
constraints for different cases.Comment: 10 page
Weak Interaction Rates Of sd-Shell Nuclei In Stellar Environment Calculated in the Proton-Neutron Quasiparticle Random Phase Approximation
Allowed weak interaction rates for sd-shell nuclei in stellar environment are
calculated using a generalized form of proton-neutron quasiparticle RPA model
with separable Gamow-Teller forces. Twelve different weak rates are calculated
for each nucleus as a function of temperature and density. This project
consists of calculation of weak rates for a total of 709 nuclei with masses
ranging from A = 18 to 100. This paper contains calculated weak rates for
sd-shell nuclei. The calculated capture and decay rates take into consideration
the latest experimental energy levels and ft value compilations. The results
are also compared with earlier works. Particle emission processes from excited
states, previously ignored, are taken into account, and are found to
significantly affect some beta decay rates.Comment: 64 pages, 17 figures, rate tables are presented in an abbreviated
form to save space. Complete rate tables can be seen in the original pape
Implications of observed neutrinoless double beta decay
Recently a positive indication of the neutrinoless double beta decay has been
announced. We study the implications of this result taking into consideration
earlier results on atmospheric neutrinos and solar neutrinos. We also include
in our discussions the recent results from SNO and K2K. We point out that on
the confidence level given for the double beta signal, the neutrino mass
matrices are now highly constrained. All models predicting Dirac masses are
ruled out and leptogenesis becomes a natural choice. Only the degenerate and
the inverted hierarchical solutions are allowed for the three generation
Majorana neutrinos. In both these cases we find that the radiative corrections
destabilize the solutions and the LOW, VO and Just So solutions of the solar
neutrinos are ruled out. For the four generation case only the inverted
hierarchical scenario is allowed.Comment: 16 pages, 2 postscript figure
Neutrino mixing schemes and neutrinoless double beta decay
We study the possible structure of the neutrino mass matrix taking into
consideration the solar and atmospheric neutrinos and the neutrinoless double
beta decay. We emphasize on mass matrices with vanishing elements. There are
only a very few possibilities remaining at present. We concentrate on three
generation scenarios and find that with three parameters there are few
possibilities with and without any vanishing elements. For completeness we also
present a five parameter four neutrino (with one sterile neutrino) mass matrix
which can explain all these experiments and the LSND result.Comment: 12 pages late
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