989 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
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
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
New features of collective motion of intrinsic degrees of freedom. Toward a possible way to classify the intrinsic states
Three exactly solvable Hamiltonians of complex structure are studied in the
framework of a semi-classical approach. The quantized trajectories for
intrinsic coordinates correspond to energies which may be classified in
collective bands. For two of the chosen Hamiltonians the symmetry SU2xSU2 is
the appropriate one to classify the eigenvalues in the laboratory frame.
Connections of results presented here with the molecular spectrum and
Moszkowski model are pointed out. The present approach suggests that the
intrinsic states, which in standard formalisms are heading rotational bands,
are forming themselves "rotational" bands, the rotations being performed in a
fictious boson space.Comment: 33 pages, 9 figure
Analysis of the rare semileptonic B_c \rar P(D,D_s) l^{+}l^{-}/\nu\bar{\nu} decays within QCD sum rules
Considering the gluon condensate corrections, the form factors relevant to
the semileptonic rare B_c \rar D,D_s(J^{P}=0^{-}) l^{+}l^{-} with
and B_c \rar D,D_s(J^{P}=0^{-})\nu\bar{\nu} transitions are
calculated in the framework of the three point QCD sum rules. The heavy quark
effective theory limit of the form factors are computed. The branching fraction
of these decays are also evaluated and compared with the predictions of the
relativistic constituent quark model. Analyzing of such type transitions could
give useful information about the strong interactions inside the pseudoscalar
meson and its structure.Comment: 32 Pages, 8 Figures and 6 Table
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