849 research outputs found
Heavy Quark Spin Symmetry and Heavy Baryons: Electroweak Decays
Heavy quark spin symmetry is discussed in the context of single and doubly
heavy baryons. A special attention is paid to the constraints/simplifications
that this symmetry imposes on the non-relativistic constituent quark model wave
functions and on the b->c semileptonic decays of these hadrons.Comment: Presented at the 21st European Conference on Few-Body Problems in
Physics, Salamanca, Spain, 30 August - 3 September 201
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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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
Mixing angle of doubly heavy baryons in QCD
We calculate the mixing angles between the spin--1/2,
-- and -- states of
doubly heavy baryons within the QCD sum rules method. It is found that the
mixing angles are large and have the values
and , respectively. The mixing angles are
slightly smaller compared to the predictions of the non--relativistic quark
model, and .Comment: 6 Page
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
Proceedings of the 2nd Iberian Nuclear Astrophysics Meeting on Compact Stars
This volume contains most of the links to the presentations delivered at this
international workshop. This meeting was the second in the series following the
previous I Encuentro Ib\'erico de Compstar, held at the University of Coimbra,
Portugal in 2010. The main purpose of this meeting was to strengthen the
scientific collaboration between the participants of the Iberian and the rest
of the southern European branches of the European Nuclear Astrophysics network,
formerly, COMPSTAR. This ESF (European Science Foundation) supported network
has been crucial in helping to make a broader audience for the the most
interesting and relevant research lines being developed currently in Nuclear
Astrophysics, especially related to the physics of neutron stars. The program
of the meeting was tailored to theoretical descriptions of the physics of
neutron stars although some input from experimental observers and other
condensed matter and optics areas of interest was also included.Comment: Journal of Physics: Conference Series Volume 342 (2012), Proceedings
of the 2nd Iberian Nuclear Astrophysics Meeting on Compact Stars, 22-23
September 2011, Salamanca-Spain. Editors, M. A. Perez-Garcia, J. Pons and C.
Albertus Editor
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