6,758 research outputs found
Chiral Lagrangian with Heavy Quark-Diquark Symmetry
We construct a chiral Lagrangian for doubly heavy baryons and heavy mesons
that is invariant under heavy quark-diquark symmetry at leading order and
includes the leading O(1/m_Q) symmetry violating operators. The theory is used
to predict the electromagnetic decay width of the J=3/2 member of the ground
state doubly heavy baryon doublet. Numerical estimates are provided for doubly
charm baryons. We also calculate chiral corrections to doubly heavy baryon
masses and strong decay widths of low lying excited doubly heavy baryons.Comment: 20 pages, no figure
Two-particle decays of B_c meson into charmonium states
The factorization of hard and soft contributions into the hadronic decays of
B_c meson at large recoils is explored in order to evaluate the decay rates
into the S, P and D-wave charmonia associated with rho and pi. The constraints
of approach applicability and uncertainties of numerical estimates are
discussed. The mode with the J/psi in the final state is evaluated taking into
account the cascade radiative electromagnetic decays of excited P-wave states,
that enlarges the branching ratio by 20-25%.Comment: 13 pages, LaTeX axodraw-style, 1 figure, 2 table
Semileptonic transition in three--point QCD sum rules and HQET with gluon condensate corrections
Taking into account the gluon condensate contributions, the form factors of
the semileptonic transition with are
calculated in the framework of the three point QCD sum rules. The heavy quark
effective theory limit of the form factors are also computed. The relevant
total decay width as well as the branching ratio are evaluated and compared
with the predictions of the other non-perturbative approaches.Comment: 27 Pages, 4 Figures and 4 Table
Light-cone sum rules for the transitions for real photons
We examine the radiative transition at the real photon
point using the framework of light-cone QCD sum rules. In particular,
the sum rules for the transition form factors and are
determined up to twist 4. The result for agrees with experiment within
10% accuracy. The agreement for is also reasonable. In addition, we
derive new light-cone sum rules for the magnetic moments of nucleons, with a
complete account of twist-4 corrections based on a recent reanalysis of photon
distribution amplitudes.Comment: 34 pages, 9 figures, revised version, published in Phys. Rev. D, one
misplaced reference correcte
Observations on the radiative corrections to pion beta-decay
We find that, in the local V-A theory, the radiative corrections to pion
beta-decay involving the weak vector current, when evaluated in the current
algebra (CA) formulation in which quarks are the fundamental underlying fields,
show a small difference with the more elementary calculations based directly on
the pion fields. We show that this difference arises from a specific
short-distance effect that depends on the algebra satisfied by the weak and
electromagnetic currents. On the other hand, we present a simple theoretical
argument that concludes that this difference does not occur when the CA
formulation is compared with the chiral perturbation theory (chiPT) approach.
Comparisons with previous studies, and with a more recent calculation based on
chiPT, are included. We also briefly review the important differences between
the results in the local V-A theory and the Standard Model.Comment: 5 pages, 1 figure. V2: two paragraphs have been added in Section III.
Final version on PR
Spectroscopy of doubly charmed baryons: and
Using the quark-diquark approximation in the framework of Buchm\" uller-Tye
potential model, we investigate the spectroscopy of doubly charmed baryons:
and . Our results include the masses, parameters
of radial wave functions of states with the different excitations of both
diquark and light quark-diquark system. We calculate the values of fine and
hyperfine splittings of these levels and discuss some new features, connected
to the identity of heavy quarks, in the dynamics of hadronic and radiative
transitions between the states of these baryons.Comment: 10 pages, Latex file, 1 fig, corrected some typo
Elastic scattering theory and transport in graphene
Electron properties of graphene are described in terms of Dirac fermions.
Here we thoroughly outline the elastic scattering theory for the
two-dimensional massive Dirac fermions in the presence of an axially symmetric
potential. While the massless limit is relevant for pristine graphene, keeping
finite mass allows for generalizations onto situations with broken symmetry
between the two sublattices, and provides a link to the scattering theory of
electrons in a parabolic band. We demonstrate that the Dirac theory requires
short-distance regularization for potentials which are more singular than 1/r.
The formalism is then applied to scattering off a smooth short-ranged
potential. Next we consider the Coulomb potential scattering, where the Dirac
theory is consistent for a point scatterer only for the effective impurity
strength below 1/2. From the scattering phase shifts we obtain the exact
Coulomb transport cross-section in terms of the impurity strength. The results
are relevant for transport in graphene in the presence of impurities that do
not induce scattering between the Dirac points in the Brillouin zone.Comment: 17 pages, 4 figures. Published versio
Analysis of the rare semileptonic B_c \rar P(D,D_s) l^{+}l^{-}/\nu\bar{\nu} decays within QCD sum rules
Considering the gluon condensate corrections, the form factors relevant to
the semileptonic rare B_c \rar D,D_s(J^{P}=0^{-}) l^{+}l^{-} with
and B_c \rar D,D_s(J^{P}=0^{-})\nu\bar{\nu} transitions are
calculated in the framework of the three point QCD sum rules. The heavy quark
effective theory limit of the form factors are computed. The branching fraction
of these decays are also evaluated and compared with the predictions of the
relativistic constituent quark model. Analyzing of such type transitions could
give useful information about the strong interactions inside the pseudoscalar
meson and its structure.Comment: 32 Pages, 8 Figures and 6 Table
A relativistic quark model for the Omega- electromagnetic form factors
We compute the Omega- electromagnetic form factors and the decuplet baryon
magnetic moments using a quark model application of the Covariant Spectator
Theory. Our predictions for the Omega- electromagnetic form factors can be
tested in the future by lattice QCD simulations at the physical strange quark
mass.Comment: 13 pages, 5 figure
SU(3) symmetry breaking in decay constants and electromagnetic properties of pseudoscalar heavy mesons
In this paper, the decay constants and mean square radii of pseudoscalar
heavy mesons are studied in the SU(3) symmetry breaking. Within the light-front
framework, the ratios and are individually
estimated using the hyperfine splittings in the and
states and the light quark masses, (), to
extract the wave function parameter . The values and are obtained, which are not only
chiefly determined by the ratio of light quark masses , but also
insensitive to the heavy quark masses and the decay constants
. The dependence of on with the
varied charm quark masses is also shown. In addition, the mean square radii are
estimated as well. The values and are obtained, and the sensitivities of on
the heavy and light quark masses are similar to those of the decay constants.Comment: 21 pages, 5 figures, 4 tables, some typos are corrected, version to
be published in Phys. Rev.
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