50,909 research outputs found
Charm mixing in the Standard Model and beyond
The motivation most often cited in searches for D0-anti-D0 mixing and
CP-violation in charm system lies with the possibility of observing a signal
from New Physics which dominates that from the Standard Model. We review recent
theoretical predictions and experimental constraints on D0-anti-D0 mixing
parameters, concentrating on possible effects of New Physics.Comment: 8 pages, 2 figures, Invited talk at International Workshop on
Tau-Charm Physics (Charm 2006), Beijing, China, 5-7 Jun 200
B_s decays at Belle
We report recent results obtained with the Belle detector using a 23.6
fb^{-1} data sample collected on the Y(5S) resonance at the KEKB asymmetric
energy e^+ e^- collider. Inclusive semileptonic B_s^0 -> X^+ l^- \nu decays are
studied for the first time and the branching fraction is measured. Combining
the electron and muon channels, we obtain Bf(B_s^0 -> X^+ l^- \nu) = (10.2 \pm
0.8 \pm 0.9)%. Also, the radiative penguin decay B_s^0 -> \phi \gamma is
observed for the first time, and an improved upper limit for the decay B_s^0
\to \gamma \gamma is obtained.Comment: Proceedings of the EPS/HEP 2007 Conference, Manchester, England, July
2007 (on behalf of the Belle collaboration), 3 pages, 2 figure
Invisible Z decay width bounds on active-sterile neutrino mixing in the (3+1) and (3+2) models
In this work we consider the standard model extended with singlet sterile
neutrinos with mass in the eV range and mixed with the active neutrinos. The
active-sterile neutrino mixing renders new contributions to the invisible Z
decay width which, in the case of light sterile neutrinos, depends on the
active-sterile mixing matrix elements only. We then use the current
experimental value of the invisible Z decay width to obtain bounds on these
mixing matrix elements for both (3+1) and (3+2) models.Comment: 10 pages, 5 figure
Geometric Mean Neutrino Mass Relation
Present experimental data from neutrino oscillations have provided much
information about the neutrino mixing angles. Since neutrino oscillations only
determine the mass squared differences , the
absolute values for neutrino masses can not be determined using data just
from oscillations. In this work we study implications on neutrino masses from a
geometric mean mass relation which enables one to
determined the absolute masses of the neutrinos. We find that the central
values of the three neutrino masses and their errors to be , , and . Implications for cosmological observation, beta decay and
neutrinoless double beta decays are discussed.Comment: 7 pages. Talk given at COSPA06. A reference adde
Summary of Experimental Meson Physics
A summary of the present experimental status of meson physics is presented.
The presentation includes the new results presented at the MESON06 workshop, as
well as other recent experimental developments in the field.Comment: 15 pages, 6 figures, presented at 9th International Workshop on Meson
Production, Properties and Interaction, Krakow, Poland, June 200
One-pion exchange current corrections for nuclear magnetic moments in relativistic mean field theory
The one-pion exchange current corrections to isoscalar and isovector magnetic
moments of double-closed shell nuclei plus and minus one nucleon with
and 41 have been studied in the relativistic mean field (RMF)
theory and compared with previous relativistic and non-relativistic results. It
has been found that the one-pion exchange current gives a negligible
contribution to the isoscalar magnetic moments but a significant correction to
the isovector ones. However, the one-pion exchange current doesn't improve the
description of nuclear isovector magnetic moments for the concerned nuclei.Comment: 9 pages, 1 figure, 3 table
Theoretical overview on tau physics
Precise measurements of the tau lepton properties provide stringent tests of
the Standard Model structure and accurate determinations of its parameters. We
overview the present status of a few selected topics: lepton universality, QCD
tests and the determination of alpha_s, m_s and V_us from hadronic tau decays,
and lepton flavor violation phenomena.Comment: Invited talk at the International Workshop on Tau-Charm Physics
(Charm2006), Beijing, China, June 5-7, 2006. 8 pages, 2 figure
The unit of electric charge and the mass hierarchy of heavy particles
We propose some empirical formulae relating the masses of the heaviest
particles in the standard model (the W,Z,H bosons and the t quark) to the
charge of the positron and the Higgs condensate v. The relations for the
masses of gauge bosons m_W = (1+e)v/4 and m_Z=sqrt{(1+e^2)/2}*(v/2) are in
excellent agreement with experimental values. By requiring the electroweak
standard model to be free from quadratic divergencies at the one-loop level, we
find: m_t=v/sqrt{2} and m_H=v/sqrt{2e}, or the very simple ratio (m_t/m_H)^2=e.Comment: 6 page
In-plane thermal conductivity of large single crystals of Sm-substituted (YSm)BaCuO
We have investigated the in-plane thermal conductivity of
large single crystals of optimally oxygen-doped
(Y,Sm)BaCuO (=0, 0.1, 0.2 and 1.0)
and YBa(CuZn)O(=0.0071) as functions
of temperature and magnetic field (along the c axis). For comparison, the
temperature dependence of for as-grown crystals with the
corresponding compositions are presented.
The nonlinear field dependence of for all crystals was observed
at relatively low fields near a half of . We make fits of the
data to an electron contribution model, providing both the mean
free path of quasiparticles and the electronic thermal conductivity
, in the absence of field. The local lattice distortion due to the
Sm substitution for Y suppresses both the phonon and electron contributions. On
the other hand, the light Zn doping into the CuO planes affects solely
the electron component below , resulting in a substantial decrease in
.Comment: 7 pages,4 figures,1 tabl
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