41,870 research outputs found
Charmless Decays Based on the six-quark Effective Hamiltonian with Strong Phase Effects II
We provide a systematic study of charmless decays (
and denote pseudoscalar and vector mesons, respectively) based on an
approximate six-quark operator effective Hamiltonian from QCD. The calculation
of the relevant hard-scattering kernels is carried out, the resulting
transition form factors are consistent with the results of QCD sum rule
calculations. By taking into account important classes of power corrections
involving "chirally-enhanced" terms and the vertex corrections as well as weak
annihilation contributions with non-trivial strong phase, we present
predictions for the branching ratios and CP asymmetries of decays into
PP, PV and VV final states, and also for the corresponding polarization
observables in VV final states. It is found that the weak annihilation
contributions with non-trivial strong phase have remarkable effects on the
observables in the color-suppressed and penguin-dominated decay modes. In
addition, we discuss the SU(3) flavor symmetry and show that the symmetry
relations are generally respected
Efficient Semidefinite Branch-and-Cut for MAP-MRF Inference
We propose a Branch-and-Cut (B&C) method for solving general MAP-MRF
inference problems. The core of our method is a very efficient bounding
procedure, which combines scalable semidefinite programming (SDP) and a
cutting-plane method for seeking violated constraints. In order to further
speed up the computation, several strategies have been exploited, including
model reduction, warm start and removal of inactive constraints.
We analyze the performance of the proposed method under different settings,
and demonstrate that our method either outperforms or performs on par with
state-of-the-art approaches. Especially when the connectivities are dense or
when the relative magnitudes of the unary costs are low, we achieve the best
reported results. Experiments show that the proposed algorithm achieves better
approximation than the state-of-the-art methods within a variety of time
budgets on challenging non-submodular MAP-MRF inference problems.Comment: 21 page
CP Violation and Strong Phases from Penguins in Decays
We calculate direct CP-violating observables in charged decays
arising from the interference of amplitudes with different strong and CKM
phases. The perturbative strong phases develop at order from
absorptive parts of one-loop matrix elements of the next-to-leading logarithm
corrected effective Hamiltonian. CPT constraints are maintained. Based on this
model, we find that partial rate asymmetries between charge conjugate
decays can be as high as 15-30\% for certain channels with branching ratios in
the range. The small values of the coefficients of angular
correlations, which we calculated previously to be of order , are not
significantly degraded by the strong phases. The charge asymmetries of rates
and angular distributions would provide unambiguous evidence for direct CP
violation.Comment: 24 pages, 3 figures (upon request), LaTeX, preprint DESY 93-19
CP Asymmetry of in Low Invariant Mass Region
I analyzed the CP asymmetry of based on model-independent
analysis which includes twelve independent four Fermi operators. The CP
asymmetry is suppressed in the Standard Model, however, if some new physics
make it much larger, the present or the next generation B factories may catch
the CP violation in this decay mode. In this paper, we studied the correlation
of the asymmetry and the branching ratio, and then we will find only a type of
interactions can be enlarge the asymmetry. Therefore, in comparison with
experiments, we have possibility that we can constrain models beyond the
standard model.Comment: 12 pages, 5 figures, LaTeX, Accepted for Physical Review
Model-Independent Analysis of B -> pi K Decays and Bounds on the Weak Phase gamma
A general parametrization of the amplitudes for the rare two-body decays B ->
pi K is introduced, which makes maximal use of theoretical constraints arising
from flavour symmetries of the strong interactions and the structure of the
low-energy effective weak Hamiltonian. With the help of this parametrization, a
model-independent analysis of the branching ratios and direct CP asymmetries in
the various B -> pi K decay modes is performed, and the impact of hadronic
uncertainties on bounds on the weak phase gamma = arg(Vub*) is investigated.Comment: 34 pages, 18 figures, uses JHEP.cls; submitted to JHE
The complexity of dynamics in small neural circuits
Mean-field theory is a powerful tool for studying large neural networks.
However, when the system is composed of a few neurons, macroscopic differences
between the mean-field approximation and the real behavior of the network can
arise. Here we introduce a study of the dynamics of a small firing-rate network
with excitatory and inhibitory populations, in terms of local and global
bifurcations of the neural activity. Our approach is analytically tractable in
many respects, and sheds new light on the finite-size effects of the system. In
particular, we focus on the formation of multiple branching solutions of the
neural equations through spontaneous symmetry-breaking, since this phenomenon
increases considerably the complexity of the dynamical behavior of the network.
For these reasons, branching points may reveal important mechanisms through
which neurons interact and process information, which are not accounted for by
the mean-field approximation.Comment: 34 pages, 11 figures. Supplementary materials added, colors of
figures 8 and 9 fixed, results unchange
Analysis of Supersymmetric Effects on B -> phi K Decays in the PQCD Approach
We study the effects of the MSSM contribution on B -> phi K decays using the
perturbative QCD approach. In this approach, strong phases can be calculated,
so that we can predict the values of CP asymmetries with the MSSM contribution.
We predict a large relative strong phase between the penguin amplitude and the
chromomagnetic penguin amplitude. If there is a new CP violating phase in the
chromomagnetic penguin amplitude, then the CP asymmetries may change
significantly from the SM prediction. We parametrize the new physics
contributions that appear in the Wilson coefficients. We maximize the new
physics parameters up to the point where it is limited by experimental
constraints. In the case of the LR insertion, we find that the direct CP
asymmetries can reach about 85% and the indirect CP asymmetry can reach about
-30%.Comment: 18 pages, 9 figures, REVTeX, Minor changes, Version to appear in
Phys. Rev.
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