2,883 research outputs found
Effects of Geometrical Symmetry on the Vortex Nucleation and Penetration in Mesoscopic Superconductors
We investigate how the geometrical symmetry affects the penetration and
arrangement of vortices in mesoscopic superconductors using self-consistent
Bogoliubov-de Gennes equations. We find that the entrance of the vortex happens
when the current density at the hot spots reaches the depairing current
density. Through determining the spatial distribution of hot spots, the
geometrical symmetry of the superconducting sample influences the nucleation
and entrance of vortices. Our results propose one possible experimental
approach to control and manipulate the quantum states of mesoscopic
superconductors with their topological geometries, and they can be easily
generalized to the confined superfluids and Bose-Einstein condensates
from the semileptonic decay and the properties of the meson distribution amplitude
The improved QCD light-cone sum rule (LCSR) provides an effective way to deal
with the heavy-to-light transition form factors (TFFs). Firstly, we adopt the
improved LCSR approach to deal with the TFF up to twist-4
accuracy. Due to the elimination of the most uncertain twist-3 contribution and
the large suppression of the twist-4 contribution, the obtained LCSR shall
provide us a good platform for testing the -meson leading-twist DA. For the
purpose, we suggest a new model for the -meson leading-twist DA
(), whose longitudinal behavior is dominantly determined by a
parameter . Moreover, we find its second Gegenbauer moment .
Varying within certain region, one can conveniently mimic the -meson DA
behavior suggested in the literature. Inversely, by comparing the estimations
with the experimental data on the -meson involved processes, one can get a
possible range for the parameter and a determined behavior for the
-meson DA. Secondly, we discuss the TFF at the maximum recoil
region and present a detailed comparison of it with the pQCD estimation and the
experimental measurements. Thirdly, by applying the LCSR on , we
study the CKM matrix element \Vcb together with its uncertainties by adopting
two types of processes, i.e. the -type and the -type.
It is noted that a smaller shows a better agreement with the
experimental value on \Vcb. For example, for the case of , we obtain
and , whose first (second)
uncertainty comes from the squared average of the mentioned theoretical
(experimental) uncertainties.Comment: 13 pages, 10 figures. Reference updated and discussion improved. To
be published in Nucl.Phys.
Twist-3 light-cone distribution amplitudes of the scalar mesons within the QCD sum rules and their application to the transition form factors
We investigate the twist-3 light-cone distribution amplitudes (LCDAs) of the
scalar mesons , and within the QCD sum rules. The QCD
sum rules are improved by a consistent treatment of the sizable -quark mass
effects within the framework of the background field approach. Adopting the
valence quark component as the dominant structure of the
scalar mesons, our estimation for their masses are close to the measured
, and . From the sum rules, we obtain
the first two non-zero moments of the twist-3 LCDAs :
and ; those of the twist-3 LCDAs
: and ; and those of the twist-3 LCDAs :
and , respectively. As an
application of those twist-3 LCDAs, we study the transition form
factors by introducing proper chiral currents into the correlator, which is
constructed such that the twist-3 LCDAs give dominant contribution and the
twist-2 LCDAs make negligible contribution. Our results of the
transition form factors at the large recoil region are
consistent with those obtained in the literature, which inversely shows the
present twist-3 LCDAs are acceptable.Comment: 14 pages, 12 figures, 7 table
The -meson longitudinal leading-twist distribution amplitude
In the present paper, we suggest a convenient model for the vector
-meson longitudinal leading-twist distribution amplitude
, whose distribution is controlled by a single parameter
. By choosing proper chiral current in the correlator, we obtain
new light-cone sum rules (LCSR) for the TFFs , and ,
in which the -order provides dominant
contributions. Then we make a detailed discussion on the
properties via those TFFs. A proper choice of can
make all the TFFs agree with the lattice QCD predictions. A prediction of
has also been presented by using the extrapolated TFFs, which
indicates that a larger leads to a larger . To
compare with the BABAR data on , the longitudinal leading-twist
DA prefers a doubly-humped behavior.Comment: 7 pages, 3 figures. Discussions improved and references updated. To
be published in Phys.Lett.
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