934 research outputs found
B_c meson rare decays in the light-cone quark model
We investigate the rare decays
and in the framework of the
light-cone quark model (LCQM). The transition form factors are calculated in
the space-like region and then analytically continued to the time-like region
via exponential parametrization. The branching ratios and longitudinal lepton
polarization asymmetries (LPAs) for the two decays are given and compared with
each other. The results are helpful to investigating the structure of
meson and to testing the unitarity of CKM quark mixing matrix. All these
results can be tested in the future experiments at the LHC.Comment: 9 pages, 11 figures, version accepted for publication in EPJ
A Two-Step Quantum Direct Communication Protocol Using Einstein-Podolsky-Rosen Pair Block
A protocol for quantum secure direct communication using blocks of EPR pairs
is proposed. A set of ordered EPR pairs is used as a data block for sending
secret message directly. The ordered EPR set is divided into two particle
sequences, a checking sequence and a message-coding sequence. After
transmitting the checking sequence, the two parties of communication check
eavesdropping by measuring a fraction of particles randomly chosen, with random
choice of two sets of measuring bases. After insuring the security of the
quantum channel, the sender, Alice encodes the secret message directly on the
message-coding sequence and send them to Bob. By combining the checking and
message-coding sequences together, Bob is able to read out the encoded messages
directly. The scheme is secure because an eavesdropper cannot get both
sequences simultaneously. We also discuss issues in a noisy channel.Comment: 8 pages and 2 figures. To appear in Phys Rev
Separability and entanglement in 2x3xN composite quantum systems
The separability and entanglement of quantum mixed states in \Cb^2 \otimes
\Cb^3 \otimes \Cb^N composite quantum systems are investigated. It is shown
that all quantum states with positive partial transposes and rank
are separable.Comment: Latex, 15 page
Study of f_0(980) and f_0(1500) from B_s \to f_0(980)\pi, f_0(1500)\pi Decays
In this paper, we analyze the scalar mesons and from
the decays within Perturbative
QCD approach. From the leading order calculations, we find that (a) in the
allowed mixing angle ranges, the branching ratio of is about , which is smaller than
that of (the difference is a few times even one
order); (b) the decay is better to distinguish
between the lowest lying state or the first excited state for ,
because the branching ratios for two scenarios have about one-order difference
in most of the mixing angle ranges; and (c) the direct CP asymmetries of for two scenarios also exists great difference. In
scenario II, the variation range of the value according to the mixing angle is very small, except for
the values corresponding to the mixing angles being near or
, while the variation range of in scenario I is very large. Compared with the future data for
the decay , it is ease to determine the nature
of the scalar meson .Comment: 16 pages, 3 figures, Revte
Effects of Allelic Variation in Glutenin Subunits and Gliadins on Baking-Quality in Near-isogenic Lines of Common Wheat cv. Longmai 19
Two lines, L-19-613 and L-19-626, were produced from the common wheat cultivar Longmai 19 (L-19) by six consecutive backcrosses using biochemical marker-assisted selection. L-19 (Glu-D1a, Glu-A3c/Gli-A1?; Gli-A1? is a gene coding for unnamed gliadin) and L-19-613 (Glu-D1d, Glu-A3c/Gli-A1?) formed a set of near-isogenic lines (NILs) for HMW-GS, while L-19-613 and L-19-626 (Glu-D1d, Glu-A3e/Gli-A1m) constituted another set of NILs for the LMW-GS/gliadins. The three L-19 NILs were grown in the wheat breeding nursery in 2007 and 2008. The field experiments were designed using the three-column contrast arrangement method with four replicates. The three lines were ranked as follows for measurements of gluten strength, which was determined by the gluten index, Zeleny sedimentation, the stability and breakdown time of the farinogram, the maximum resistance and area of the extensogram, and the P andWvalues of the alveogram: L-19-613 > L-19-626 > L-19. The parameters listed above were significantly different between lines at the 0.05 or 0.01 level. The Glu-D1 and Glu-A3/Gli-A1 loci had additive effects on the gluten index, Zeleny sedimentation, stability, breakdown time, maximum resistance, area, P and W values. Although genetic variation at the Glu-A3/Gli-A1 locus had a great influence on wheat quality, the genetic difference between Glu-D1d and Glu-D1a at the Glu-D1 locus was much larger than that of Glu-A3c/Gli-A1? and Glu-A3e/Gli-A1m at the Glu-A3/Gli-A1 locus. Glu-D1d had negative effects on the extensibility and the L value compared with Glu-D1a. In contrast, Glu-A3c/Gli-A1? had a positive effect on these traits compared with Glu-A3e/Gli-A1m
Lepton Flavor Violation in the SUSY-GUT Models with Lopsided Mass Matrix
The tiny neutrino masses measured in the neutrino oscillation experiments can
be naturally explained by the supersymmetric see-saw mechanism. If the
supersymmetry breaking is mediated by gravity, the see-saw models may predict
observable lepton flavor violating effects. In this work, we investigate the
lepton flavor violating process in the kind of neutrino mass
models based on the idea of the ``lopsided'' form of the charged lepton mass
matrix. The constraints set by the muon anomalous magnetic moment are taken
into account. We find the present models generally predict a much larger
branching ratio of than the experimental limit. Conversely,
this process may give strong constraint on the lepton flavor structure.
Following this constraint we then find a new kind of the charged lepton mass
matrix. The feature of the structure is that both the elements between the 2-3
and 1-3 generations are ``lopsided''. This structure produces a very small 1-3
mixing and a large 1-2 mixing in the charged lepton sector, which naturally
leads to small and the LMA solution for the solar neutrino
problem.Comment: 24 pages, 8 figure
Landau Theory of the Phase Transitions in Half Doped Manganites: Interplay of Magnetic, Charge and Structural Orders
The order parameters of the magnetic, charge and structural orders at
half-doped manganites are identified. A corresponding Landau theory of the
phase transitions is formulated. Many structural and thermodynamical behaviors
are accounted for and clarified within the framework. In particular, the theory
provides a unified picture for the scenario of the phase transitions and their
nature with respect to the variation of the tolerance factor of the manganites.
It also accounts for the origin of the incommensurate nature of the orbital
order and its subsequently accompanying antiferromagnetic order.Comment: 4 pages, 3 eps figures, Revtex, Phys. Rev. B61, 200
Specific Heat Discontinuity in Impure Two-Band Superconductors
The Ginzburg-Landau coefficients, and the jump of the specific heat are
calculated for a disordered two-band superconductor. We start with the analysis
of a more general case arbitrary anisotropy. While the specific heat
discontinuity at the critical temperature T_c decreases with increasing
disorder, its ratio to the normal state specific heat at T_c increases and
slowly converges to the isotropic value. For a strong disorder the deviation
from the isotropic value is proportional to the elastic electron scattering
time. In the case of a two-band superconductor we apply a simplified model of
the interaction independent on momentum within a band. In the framework of this
model all thermodynamic values can be found explicitly at any value of the
scattering rate. This solution explains the sample dependence of the specific
heat discontinuity in MgB_2 and the influence of the disorder on the critical
temperature.Comment: New results relate to two-band superconductors, 9 pages, 2 figure
Interference-induced gain in Autler-Townes doublet of a V-type atom in a cavity
We study the Autler-Townes spectrum of a V-type atom coupled to a
single-mode, frequency-tunable cavity field at finite termperature, with a
pre-selected polarization in the bad cavity limit, and show that, when the mean
number of thermal photons and the excited sublevel splitting is very
large (the same order as the cavity linewidth), the probe gain may occur at
either sideband of the doublet, depending on the cavity frequency, due to the
cavity-induced interference.Comment: Minor changes are mad
Cavity implementation of quantum interference in a -type atom
A scheme for engineering quantum interference in a -type atom
coupled to a frequency-tunable, single-mode cavity field with a pre-selected
polarization at finite temperature is proposed. Interference-assisted
population trapping, population inversions and probe gain at one sideband of
the Autler-Townes spectrum are predicted for certain cavity resonant
frequencies.Comment: 2 postscript figures are adde
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