1,116 research outputs found
Double Beta Decay, Nuclear Structure and Physics beyond the Standard Model
Neutrinoless Double Beta Decay () is presently the only known
experiment to distinguisch between Dirac neutrinos, different from their
antiparticles, and Majorana neutrinos, identical with their antiparticles. In
addition allows to determine the absolute scale of the
neutrino masses. This is not possible with neutrino oscillations. To determine
the neutrino masses one must assume, that the light Majorana neutrino exchange
is the leading mechanism for and that the matrix element of
this transition can ba calculated reliably. The experimental
transition amplitude in this mechanism is a product of the light left handed
effective Majorana neutrino mass and of this transition matrix element. The
different methods, Quasi-particle Random Phase Approximation (QRPA), Shell
Model (SM), Projected Hartree-Fock-Bogoliubov (PHFB) and Interacting Boson
Model (IBM2) used in the literature and the reliability of the matrix elements
in these approaches are reviewed. In the second part it is investigated how one
can determine the leading mechanism or mechanisms from the data of the
decay in different nuclei. Explicite expressions are given for
the transition matrix elements. is shown, that possible interference terms
allow to test CP (Charge and Parity conjugation) violation.Comment: Contribution to the EPS conference in Eilath: "Nuclear Physics in
Astrophysics 5." April 3rd to 8th. 201
Dibaryon Condensate in Nuclear Matter and Neutron Stars: Exact Analysis in One-Dimensional Models
We investigate dense nuclear matter with a dibaryon Bose-Einstein condensate
as a possible intermediate state before the quark-gluon phase transition. An
exact analysis of this state of matter is presented in a one-dimensional model.
The analysis is based on a reduction of the quantization rules for the N-body
problem to N coupled algebraic transcendental equations. We observe that when
the Fermi momentum approaches the resonance momentum, the one-particle
distribution function increases near the Fermi surface. When the Fermi momentum
is increased beyond the resonance momentum, the equation of state becomes
softer. The observed behavior can be interpreted in terms of formation of a
Bose-Einstein condensate of two-fermion resonances (dibaryons). In cold nuclear
matter, it should occur if 2(m_N + epsilon_F) is greater or equal to m_D, where
m_N and m_D are respectively the nucleon and dibaryon masses and epsilon_F is
the nucleon Fermi energy.Comment: 25 pages, LaTeX, 2 Postscript figures, to appear in Annals of Physic
Gamow-Teller strength distributions for double-beta-decaying nuclei within continuum-QRPA
A version of the pn-continuum-QRPA is outlined and applied to describe the
Gamow-Teller strength distributions for -decaying open-shell
nuclei. The calculation results obtained for the pairs of nuclei Cd-Sn
and Te-Xe are compared with available experimental data.Comment: 8 pages, 3 figures, To appear in the proceedings of "Nucleus-2007:
Fundamental problems of nuclear physics, atomic power engineering and nuclear
technologies" Voronezh, Russia, June 25-29, 200
Radiative proton-antiproton annihilation and isospin mixing in protonium
A detailed analysis of the radiative annihilation is made in the
framework of a two-step formalism, the annihilates into meson
channels containing a vector meson with a subsequent conversion into a photon
via the vector dominance model (VDM). Both steps are derived from the
underlying quark model. First, branching ratios for radiative protonium
annihilation are calculated and compared with data. Then, details of the
isospin interference are studied for different models of the initial protonium
state and also for different kinematical form factors. The isospin interference
is shown to be uniquely connected to the mixing in the
protonium state. Values of the interference terms directly deduced from data
are consistent with theoretical expectations, indicating a dominant
component for the and a sizable component for the
protonium state. The analysis is extended to the
transition, where the large observed branching ratio remains unexplained in the
VDM approach.Comment: 34 pages, RevTeX, 2 figures, to appear in Phys. Rev. C; typos
correcte
Extra Dimensions and Neutrinoless Double Beta Decay Experiments
The neutrinoless double beta decay is one of the few phenomena, belonging to
the non-standard physics, which is extensively being sought for in experiments.
In the present paper the link between the half-life of the neutrinoless double
beta decay and theories with large extra dimensions is explored. The use of the
sensitivities of currently planned experiments: DAMA, CANDLES,
COBRA, DCBA, CAMEO, GENIUS, GEM, MAJORANA, MOON, CUORE, EXO, and XMASS, gives
the possibility for a non-direct `experimental' verification of various extra
dimensional scenarios. We discuss also the results of the Heidelberg--Moscow
Collaboration. The calculations are based on the Majorana neutrino mass
generation mechanism in the Arkani-Hamed--Dimopoulos--Dvali model.Comment: I've decided to move the collection of my papers to arXiv for easier
acces
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