889 research outputs found
New analysis of semileptonic B decays in the relativistic quark model
We present the new analysis of the semileptonic B decays in the framework of
the relativistic quark model based on the quasipotential approach. Decays both
to heavy D^{(*)} and light \pi(\rho) mesons are considered. All relativistic
effects are systematically taken into account including contributions of the
negative-energy states and the wave function transformation from the rest to
moving reference frame. For heavy-to-heavy transitions the heavy quark
expansion is applied. Leading and subleading Isgur-Wise functions are
determined as the overlap integrals of initial and final meson wave functions.
For heavy-to-light transitions the explicit relativistic expressions are used
to determine the dependence of the form factors on the momentum transfer
squared. Such treatment significantly reduces theoretical uncertainties and
increases reliability of obtained predictions. All results for form factors,
partial and total decay rates agree well with recent experimental data and
unquenched lattice calculations. From this comparison we find the following
values of the Cabibbo-Kobayashi-Maskawa matrix elements:
|V_{cb}|=(3.85\pm0.15\pm 0.20)*10^{-2} and
|V_{ub}|=(3.82\pm0.20\pm0.20)*10^{-3}, where the first error is experimental
and the second one is theoretical.Comment: 25 pages, 11 figure
Relativistic description of asymmetric fully heavy tetraquarks in the diquark-antidiquark model
Masses of the ground, orbitally and radially excited states of the asymmetric
fully heavy tetraquarks, composed of charm (c) and bottom (b) quarks and
antiquarks are calculated in the relativistic diquark-antidiquark picture. The
relativistic quark model based on the quasipotential approach and quantum
chromodynamics is used to construct the quasipotentials of the quark-quark and
diquark-antidiquark interactions. These quasipotentials consist of the
short-range one-gluon exchange and long-distance linear confinement
interactions. Relativistic effects are consistently taken into account. A
tetraquark is considered as a bound state of a diquark and an antidiquark which
are treated as a spatially extended colored objects and interact as a whole. It
is shown that most of the investigated tetraquarks states (including all ground
states) lie above the fall-apart strong decay thresholds into a meson pair. As
a result they can be observed as wide resonances. Nevertheless, several
orbitally excited states lie slightly above or even below these fall-apart
thresholds, thus they could be narrow states.Comment: 24 pages, 1 figur
Relativistic Description of Exclusive Semileptonic Decays of Heavy Mesons
Using quasipotential approach, we have studied exclusive semileptonic decays
of heavy mesons with the account of relativistic effects. Due to more complete
relativistic description of the quark more precise expressions for
semileptonic form factors are obtained. Various differential distributions in
exclusive semileptonic decays of heavy mesons are calculated. It is argued that
consistent account of relativistic effects and HQET motivated choice of the
parameters of quark-antiquark potential allow to get reliable value for the
ratio in the decay as well as the
ratio~. All calculated branching
ratios are in accord with available experimental data.Comment: 18 pages, LATEX, 2 figures inclosed + 4 Postscript figure
Lateral-angular and temporal characteristics of EAS optical radiation
Characteristics of the direct and scattered components of electron-photon shower optical radiation for distances R 500 m from the shower core to a detector, allowing for the Cerenkov and fluorescent mechanism of photon generation are presented. The results of calculations are employed to clarify the techniques for determination of the shower parameters detected by both installations registering fluorescent light and those recording Cerenkov light
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