10,447 research outputs found
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
Quark model study of the semileptonic B -> pi decay
The semileptonic decay B->pi is studied starting from a simple quark model
and taking into account the effect of the B* resonance. A novel, multiply
subtracted, Omn\`es dispersion relation has been implemented to extend the
predictions of the quark model to all physical q^2 values. We find
|V_{ub}|=0.0034 +/- 0.0003(exp.)+/- 0.0007(theory), in good agreement with
experiment.Comment: Three pages, two figures. To appear in the proceedings of Quark
Confinament and Hadron Spectrum VII. Azores, September 200
Redes de transmisión inteligente. Beneficios y riesgos
ResumenActualmente los sistemas eléctricos operan cada vez más cercanos a sus límites de estabilidad, es por ello que se hace necesaria y primordial la transición hacia nuevos sistemas de transmisión que garanticen la eficiente entrega de la energía eléctrica, evitando con ello cortes de energía que generan importantes pérdidas en la economía de cualquier país del mundo. En este documento se realiza un análisis de los elementos necesarios para una sana y eficiente transición de una red de transmisión eléctrica verticalmente, integrada hacia una red de transmisión inteligente. Se presenta un análisis comparativo entre dos de los marcos de referencia más importantes, el de la UE y el de EUA, en el modelo, desarrollo, beneficios y riesgos en la implementación de estos sistemas.AbstractNowadays the Power Systems are working near their stability limits, for this reason it is necessary and essential a transition to new transmission systems that ensure efficient delivery of electrical energy, with the objective to prevent “blackouts” that cause significant losses in the economy of any country in the world. This paper analyzes important elements to consider having a healthy and efficient transition from a power grid vertically integrated into a smart transmission grid. A comparative analysis in the model, development, benefits and risks of the implementation of these systems, between two of the main marc of references of smart grids, the EU and the USA is presented
Mott-Hubbard quantum criticality in paramagnetic CMR pyrochlores
We present a correlated {\it ab initio} description of the paramagnetic phase
of TlMnO, employing a combined local density approximation (LDA)
with multiorbital dynamical mean field theory (DMFT) treatment. We show that
the insulating state observed in this colossal magnetoresistance (CMR)
pyrochlore is determined by strong Mn intra- and inter-orbital local
electron-electron interactions. Hybridization effects are reinforced by the
correlation-induced spectral weight transfer. Our result coincides with optical
conductivity measurements, whose low energy features are remarkably accounted
for by our theory. Based on this agreement, we study the disorder-driven
insulator-metal transition of doped compounds, showing the proximity of
TlMnO to quantum phase transitions, in agreement with recent
measurements.Comment: 4 pages, 4 figure
CP-odd static electromagnetic properties of the W gauge boson and the t quark via the anomalous tbW coupling
In the framework of the electroweak chiral Lagrangian, the one-loop induced
effects of the anomalous coupling, which includes both left- and
right-handed complex components, on the static electromagnetic properties of
the boson and the quark are studied. The attention is focused mainly on
the CP-violating electromagnetic properties. It is found that the
anomalous coupling can induce both CP-violating moments of the boson,
namely, its electric dipole () and magnetic quadrupole
() moments. As far as the quark is concerned, a potentially
large electric dipole moment can arise due to the anomalous
coupling. The most recent bounds on the left- and right-handed parameters from
meson physics lead to the following estimates e-cm and e-cm, which
are 7 and 14 orders of magnitude larger than the standard model (SM)
predictions, whereas may be as large as e-cm, which is about 8
orders of magnitude larger than its SM counterpart.Comment: This paper has been merged with hep-ph/0612171 for publication in
Physical Review
Study of the leptonic decays of pseudoscalar and vector mesons and of the semileptonic and decays
We present results for different observables in weak decays of pseudoscalar
and vector mesons with a heavy or quark. The calculations are done in a
nonrelativistic constituent quark model improved at some instances by heavy
quark effective theory constraints. We determine pseudoscalar and vector meson
decay constants that within a few per cent satisfy , a
result expected in heavy quark symmetry when the heavy quark masses tend to
infinity. We also analyze the semileptonic and decays for
which we evaluate the different form factors. Here we impose heavy quark
effective theory constraints among form factors that are not satisfied by a
direct quark model calculation. The value of the form factors at zero recoil
allows us to determine, by comparison with experimental data, the value of the
Cabbibo-Kobayashi-Maskawa matrix element. From the
semileptonic decay we get in perfect agreement with
our previous determination based on the study of the semileptonic decay and also in excellent agreement with a recent experimental
determination by the DELPHI Collaboration. We further make use of the partial
conservation of axial current hypothesis to determine the strong coupling
constants and . The
ratio agrees with the heavy quark symmetry
prediction of 1.Comment: 19 Latex pages,6 figures, references added, corrected typos, content
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