6,405 research outputs found
Implications of R-parity violating supersymmetry for atomic and hadronic EDMs
We calculate the electric dipole moments (EDM) of the neutral Hg(199) atom,
deuteron, nucleons and neutral hyperons Lambda, Sigma(0) and Xi(0) in the
framework of a generic SUSY model without R-parity conservation (RPV SUSY) on
the basis of the SU(3) version of chiral perturbation theory (ChPT). We
consider CP-violation in the hadronic sector induced by the chromoelectric
quark dipole moments and CP-violating 4-quark effective interactions. From the
null experimental results on the neutron and Hg(199) atom EDMs we derive limits
on the imaginary parts of certain products Im(lambda' lambda'*) of the
trilinear RPV-couplings and demonstrate that they are more stringent than those
existing in the literature. Using these limits we give predictions for the EDMs
of neutral hyperons.
We also estimate the prospects of future storage ring experiments on the
deuteron EDM and show that the expected improvement of the above limits in
these experiments may reach several orders of magnitude.Comment: 11 pages, 1 figure, accepted for publication in Phys. Rev.
B_s(d) - bar B_s(d) mixing constraints on flavor changing decays of t and b quarks
We study those dimension 6 effective operators which generate flavor-changing
quark-gluon transitions of the third generation quarks, with t -> g + u(c) and
b -> g + d(s), and which could be of interest for LHC experiments. We analyze
the contribution of these operators to B_s(d) - bar B_s(d) mixing and derive
limits on the corresponding effective couplings from the existing experimental
data. The Standard Model gauge invariance relates these couplings to the
couplings controlling t -> g + u(c). On this basis we derive upper limits for
the branching ratios of these processes. We further show that forthcoming LHC
experiments might be able to probe the studied operators and the physics beyond
the Standard Model related to them.Comment: 6 pages, 1 figur
Neutrinoless double beta decay and neutrino mass hierarchies
In the framework of the see-saw mechanism the normal hierarchy is favorable
for the neutrino mass spectrum. For this spectrum we present a detailed
calculation of the half-lives of neutrinoless double beta decay for several
nuclei of experimental interest. The half-lives are evaluated by considering
the most comprehensive nuclear matrix elements, which were obtained within the
renormalized QRPA by the Bratislava-Caltech-Tuebingen group. The dependence of
the half-lives on sin^2 theta_{13}$ and the lightest neutrino mass is studied.
We present also the results of the calculations of the half-lives of
neutrinoless double beta decay in the case of the inverted hierarchy of
neutrino masses.Comment: 13 pages, 3 figure
Direct Test of the Scalar-Vector Lorentz Structure of the Nucleon- and Antinucleon-Nucleus Potential
Quantum Hadrodynamics in mean field approximation describes the effective
nucleon-nucleus potential (about -50 MeV deep) as resulting from a strong
repulsive vector (about 400 MeV) and a strong attractive scalar (about -450
MeV) contribution. This scalar-vector Lorentz structure implies a significant
lowering of the threshold for photoproduction on a nucleus by about
850 MeV as compared to the free case since charge conjugation reverses the sign
of the vector potential contribution in the equation of motion for the
states. It also implies a certain size of the photon induced
pair creation cross section near threshold which is calculated for a
target nucleus Pb. We also indicate a measurable second signature of
the photoproduction process by estimating the increased cross
section for emission of charged pions as a consequence of
annihilation within the nucleus.Comment: 18 pages latex, 5 PS figure
On the two-photon decay width of the sigma meson
We shortly report on the two-photon decay width of the light -meson
interpreted as a quarkonium state. Results are given in dependence on the
-mass and the constituent mass of the light quark. The triangle
quark-loop diagram, responsible for the two-photon transition, is carefully
evaluated: a term in the transition amplitude, often omitted in literature,
results in destructive interference with the leading term. As a result we show
that the two-photon decay width of the in the quarkonium picture is
less than 1 keV for the physical range of parameters.Comment: 6 pages, 4 figure
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