89 research outputs found
Spin Content of Lambda in QCD Sum Rules
We calculate the isoscalar axial-vector coupling constants of the Lambda
hyperon using the method of QCD sum rules. A determination of these coupling
constants reveals the individual contributions of the u, d and the s quarks to
the spin content of Lambda. Our results for the light-quark contributions are
in agreement with those from experiment assuming flavor SU(3). We also find
that the flavor-SU(3)-breaking effects are small and the contributions from the
u and the d quarks to the Lambda polarization are negatively polarized as in
the flavor-SU(3) limit.Comment: 6 pages, 2 figure
QCD Sum Rules study of meson-baryon sigma terms
The pion-baryon sigma terms and the strange-quark condensates of the octet
and the decuplet baryons are calculated by employing the method of quantum
chromodynamics (QCD) sum rules. We evaluate the vacuum-to-vacuum transition
matrix elements of two baryon interpolating fields in an external
isoscalar-scalar field and use a Monte Carlo-based approach to systematically
analyze the sum rules and the uncertainties in the results. We extract the
ratios of the sigma terms, which have rather high accuracy and minimal
dependence on QCD parameters. We discuss the sources of uncertainties and
comment on possible strangeness content of the nucleon and the Delta.Comment: 17 pages, 10 figures, to be published in Phys. Rev.
Study of FCNC mediated rare B_s decays in a single universal extra dimension scenario
We study the rare semileptonic and radiative leptonic B_s decays in the
universal extra dimension model. In this scenario, with a single extra
dimension, there exists only one new parameter beyond those of the standard
model, which is the inverse of the compactification radius R. We find that with
the additional contributions due to the KK modes the branching ratios of the
rare B_s decays are enhanced from their corresponding standard model values and
the zero point of the forward backward asymmetries are shifted towards the
left.Comment: 19 pages, 7 figures, version to appear in Phys. Rev.
Axial Charges of Octet Baryons in Two-flavor Lattice QCD
We evaluate the strangeness-conserving , , ,
and the strangeness-changing , ,
, axial charges in lattice QCD with two flavors of
dynamical quarks and extend our previous work on
pseudoscalar-meson-octet-baryon coupling constants so as to include
, and coupling constants. We find that
the axial charges have rather weak quark-mass dependence and the breaking in
SU(3)-flavor symmetry is small at each quark-mass point we consider.Comment: 6 pages, 6 figures. Added discussions and a figure; version to appear
in Physics Letters
Axial Charges of Octet Baryons in Two-flavor Lattice QCD
We evaluate the strangeness-conserving , , ,
and the strangeness-changing , ,
, axial charges in lattice QCD with two flavors of
dynamical quarks and extend our previous work on
pseudoscalar-meson-octet-baryon coupling constants so as to include
, and coupling constants. We find that
the axial charges have rather weak quark-mass dependence and the breaking in
SU(3)-flavor symmetry is small at each quark-mass point we consider.Comment: 6 pages, 6 figures. Added discussions and a figure; version to appear
in Physics Letters
transition in lattice QCD
We study the electromagnetic
transition in 2+1 flavor lattice QCD, which gives access to the dominant decay
mode of baryon. The magnetic dipole and the electric quadrupole
transition form factors are computed. The magnetic dipole form factor is found
to be mainly determined by the strange quark and the electric quadrupole form
factor to be negligibly small, in consistency with the quark model. We also
evaluate the helicity amplitudes and the decay rate.Comment: 8 pages, 1 figure. Added references and discussio
A look inside charmed-strange baryons from lattice QCD
The electromagnetic form factors of the spin-3/2 baryons, namely
, , and , are
calculated in full QCD on PACS-CS lattices with a pion mass of
156(9) MeV. The electric charge radii and magnetic moments from the and
multipole form factors are extracted. Results for the electric quadrupole
form factors, , are also given. Quark sector contributions are computed
individually for each observable and then combined to obtain the baryon
properties. We find that the charm quark contributions are systematically
smaller than the strange-quark contributions in the case of the charge radii
and magnetic moments. moments of the and
provide a statistically significant data to conclude that their electric charge
distributions are deformed to an oblate shape. Properties of the spin-1/2
and baryons are also computed and a thorough
comparison is given. This complete study gives valuable hints about the
heavy-quark dynamics in charmed hadrons.Comment: 14 pages, 14 figures. Includes a subsection on the systematic effect
CP violation in polarized B-> pi ell+ ell- and B-> rho ell+ ell- decays
We study the decay rate and the CP violating asymmetry of the exclusive B->
pi ell+ ell- and B-> rho ell+ ell- decays in the case where one of the final
leptons is polarized. We calculate the contributions coming from the individual
polarization states in order to identify a so-called wrong sign decay, which is
a decay with a given polarization, whose width and CP asymmetry are smaller as
compared to the unpolarized one. The results are presented for electron and tau
leptons. We observe that in particular decay channels, one can identify a wrong
sign decay which is more sensitive to new physics beyond the Standard Model.Comment: 24 pages, 10 figures; minor errors and misprints corrected,
references added, version to be published in EPJ
Electromagnetic properties of doubly charmed baryons in Lattice QCD
We compute the electromagnetic properties of \Xi_cc baryons in 2+1 flavor
Lattice QCD. By measuring the electric charge and magnetic form factors of
\Xi_cc baryons, we extract the magnetic moments, charge and magnetic radii as
well as the \Xi_cc \Xi_cc \rho coupling constant, which provide important
information to understand the size, shape and couplings of the doubly charmed
baryons. We find that the two heavy charm quarks drive the charge radii and the
magnetic moment of \Xi_cc to smaller values as compared to those of, e.g., the
proton.Comment: 15 pages, 5 figures; added discussions and references, version
accepted by PL
Vector and axial-vector couplings of D and D* mesons in 2+1 flavor Lattice QCD
Using the axial-vector coupling and the electromagnetic form factors of the D
and D* mesons in 2+1 flavor Lattice QCD, we compute the D*D\pi, DD\rho and
D*D*\rho coupling constants, which play an important role in describing the
charm hadron interactions in terms of meson-exchange models. We also extract
the charge radii of D and D* mesons and determine the contributions of the
light and charm quarks separately.Comment: 19 pages, 3 figures; added references and comments, published versio
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