1,991 research outputs found
Study of semileptonic and nonleptonic decays of the meson
We evaluate semileptonic and two--meson nonleptonic decays of the
meson in the framework of a nonrelativistic quark model. The former are done in
spectator approximation using one--body current operators at the quark level.
Our model reproduces the constraints of heavy quark spin symmetry obtained in
the limit of infinite heavy quark mass. For the two--meson nonleptonic decays
we work in factorization approximation. We compare our results to the ones
obtained in different relativistic approaches.Comment: Talk given at the IVth International Conference on Quarks an Nuclear
Physics, Madrid, June 5th-10th 200
Masses and semileptonic decays of doubly heavy baryons in a nonrelativistic quark model
We evaluate masses and semileptonic decay widths for the ground state of
doubly heavy and baryons in the framework of a nonrelativistic
quark model. We solve the three-body problem by means of a variational ansatz
made possible by heavy-quark spin symmetry constraints. Our masses are
comparable to the ones obtained in relativistic calculations and we get one of
the best agreements with lattice data. Our simple wave functions are used to
evaluate semileptonic decays of doubly heavy and baryons. Our results for the decay widths are in reasonable
agreement with calculations done in a relativistic calculation in the
quark-diquark approximation. We also check that our wave functions comply with
what it is expected in the infinite heavy quark mass limit.Comment: 3 latex pages, two tables. To appear in the INPC07 proceeding
Masses and semileptonic decays of doubly heavy baryons in a nonrelativistic quark model
We evaluate masses and semileptonic decay widths for the ground state of
doubly heavy and baryons in the framework of a nonrelativistic
quark model. We solve the three-body problem by means of a variational ansatz
made possible by heavy-quark spin symmetry constraints. Our masses are
comparable to the ones obtained in relativistic calculations and we get one of
the best agreements with lattice data. Our simple wave functions are used to
evaluate semileptonic decays of doubly heavy and baryons. Our results for the decay widths are in reasonable
agreement with calculations done in a relativistic calculation in the
quark-diquark approximation. We also check that our wave functions comply with
what it is expected in the infinite heavy quark mass limit.Comment: 3 latex pages, two tables. To appear in the INPC07 proceeding
Strong one-pion decay of , and
Working in the framework of a nonrelativistic quark model we evaluate the
widths for the strong one-pion decays ,
and . We take advantage of
the constraints imposed by heavy quark symmetry to solve the three-body problem
by means of a simple variational ansatz. We use partial conservation of the
axial current hypothesis to get the strong vertices from weak axial current
matrix elements. Our results are in good agreement with experimental data.Comment: 3 latex pages. Contribution to the Proceedings of the Quark
Confinement and the Hadron Spectrum VII Conference (QCHS7) Ponta Delgada (PT)
Sept 2-7, 200
Constraints on deviations from CDM within Horndeski gravity
Recent anomalies found in cosmological datasets such as the low multipoles of
the Cosmic Microwave Background or the low redshift amplitude and growth of
clustering measured by e.g., abundance of galaxy clusters and redshift space
distortions in galaxy surveys, have motivated explorations of models beyond
standard CDM. Of particular interest are models where general
relativity (GR) is modified on large cosmological scales. Here we consider
deviations from CDM+GR within the context of Horndeski gravity, which
is the most general theory of gravity with second derivatives in the equations
of motion. We adopt a parametrization in which the four additional Horndeski
functions of time are proportional to the cosmological density of
dark energy . Constraints on this extended parameter space
using a suite of state-of-the art cosmological observations are presented for
the first time. Although the theory is able to accommodate the low multipoles
of the Cosmic Microwave Background and the low amplitude of fluctuations from
redshift space distortions, we find no significant tension with CDM+GR
when performing a global fit to recent cosmological data and thus there is no
evidence against CDM+GR from an analysis of the value of the Bayesian
evidence ratio of the modified gravity models with respect to CDM,
despite introducing extra parameters. The posterior distribution of these extra
parameters that we derive return strong constraints on any possible deviations
from CDM+GR in the context of Horndeski gravity. We illustrate how our
results can be applied to a more general frameworks of modified gravity models.Comment: 22 pages; 4 figures; 9 tables. The constraints have been revised to
match the precision required according to the recently released hi_class
pape
- …