248 research outputs found
Weak Decays of Doubly Heavy Baryons:
The weak decays of a spin- doubly charm baryon () to a
spin- singly charm baryon () and a light vector meson ()
are studied under a phenomenological scheme. The contributions are classified
into different topological diagrams, among which the short distance ones are
calculated under the factorization hypothesis, and the long distance
contributions are modelled as final-state interactions (FSIs) which are
estimated with the one-particle-exchange model. In calculation the topological
contributions tend to fall in a hierarchy. The branching fractions or decay
widths are estimated, and it indicates that
and can be used as candidate
decays for searching and . Some decays that are
mainly activated by the long distance effects are found, observation on which
in future experiments can help to understand the role of FSIs in charm baryon
decays.Comment: 29 pages, 5 figures, 7 tables; version published in EPJ
Branching Ratios, Forward-backward Asymmetry and Angular Distributions of Decays
Using the form factors evaluated in the perturbative QCD approach,
we study semileptonic and decays,
where and are mixtures of and which
are and states, respectively. Using the technique of helicity
amplitudes, we express the decay amplitudes in terms of several independent and
Lorentz invariant pieces. We study the dilepton invariant mass distributions,
branching ratios, polarizations and forward-backward asymmetries of decays. The ambiguity in the sign of the mixing angle will induce
much large differences to branching ratios of semileptonic B decays: branching
ratios without resonant contributions either have the order of or
. But the polarizations and the forward-backward asymmetries are not
sensitive to the mixing angles. We find that the resonant contributions will
dramatically change the dilepton invariant mass distributions in the resonant
region. We also provide the angular distributions of decays.Comment: 14 pages, 6 figures, version appears in PR
Transition Form Factors in the PQCD approach
Under two different scenarios for the light scalar mesons, we investigate the
transition form factors of mesons decay into a scalar meson in the
perturbative QCD approach. In the large recoiling region, the form factors are
dominated by the short-distance dynamics and can be calculated using
perturbation theory. We adopt the dipole parametrization to recast the
dependence of the form factors. Since the decay constants defined by the scalar
current are large, our predictions on the form factors are much larger
than the transitions, especially in the second scenario. Contributions
from various light-cone distribution amplitudes (LCDAs) are elaborated and we
find that the twist-3 LCDAs provide more than a half contributions to the form
factors. The two terms of the twist-2 LCDAs give destructive contributions in
the first scenario while they give constructive contributions in the second
scenario. With the form factors, we also predict the decay width and branching
ratios of the semileptonic and decays. The
branching ratios of channels are found to have the order of
while those of have the order of . These
predictions can be tested by the future experiments.Comment: 20 pages, 31 figure
Transition form factors of B decays into p-wave axial-vector mesons in the perturbative QCD approach
The form factors are studied in perturbative QCD approach
( denote a vector meson and two kinds of p-wave axial-vector mesons:
and states, respectively.). The form factors are directly
studied in the large recoiling region and extrapolated to the whole kinematic
region within the dipole parametrization. Adopting decay constants with
different signs for the two kinds of axial-vectors, we find that the two kinds
of form factors have the same sign. The two strange mesons
and mix with each other via the SU(3) symmetry breaking effect. In
order to reduce the ambiguities in the mixing angle between and
, we propose a model-independent way that utilizes the B decay data.
Most of the branching fractions of the semilteptonic decays
are of the order , which still need experimental tests in the on-going
and forthcoming experiments.Comment: 22 pages, 7 figure
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