Rare B s decays in the relativistic quark model
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Regular Article - Theoretical Physics
Rare Bs decays in the relativistic quark model R.N. Faustov, V.O. Galkina Dorodnicyn Computing Centre, Russian Academy of Sciences, Vavilov Str. 40, 119333 Moscow, Russia
Received: 10 September 2013 / Published online: 8 October 2013 © Springer-Verlag Berlin Heidelberg and Società Italiana di Fisica 2013
Abstract The branchings fractions of the rare Bs decays are calculated in the framework of the QCD-motivated relativistic quark model. The form factors of the weak Bs transitions to light mesons are expressed through the overlap integral of the initial and final meson wave functions in the whole accessible kinematical range. Explicit determination of the momentum transfer dependence of the form factors without additional model assumptions and extrapolations significantly improve the reliability of the obtained results. The approximate analytical form of the form factors is given in order to simplify the comparison with other predictions and experiment. The calculated form factors are applied for the investigations of the rare semileptonic, radiative and nonleptonic Bs decays. The factorization approximation is used for the description of the non-leptonic decays. All results agree well with available experimental data.
1 Introduction The rare weak decays of Bs mesons are governed by the flavor changing neutral current. In the standard model their description requires calculation of the loop (penguin) diagrams. Thus such decays are very sensitive to the intermediate contributions of the new particles and interactions. The accurate theoretical evaluation and experimental measurement of their decay rates can significantly constrain the “new physics” models. Theoretical investigation of these rare decays is usually based on the effective Hamiltonian in which intermediate gauge bosons are integrated out. Application of the operator product expansion allows one to separate short- and longdistance effects which are assumed to factorize. The shortdistance contributions are described by the Wilson coefficients which are calculated perturbatively. The long-distance part is attributed to the set of the operators, which matrix elements between initial and final meson states are usually a e-mail:
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parametrized by the set of the invariant form factors. The calculation of these form factors requires application of the nonperturbative methods. Thus the improvement of the theoretical understanding of the rare decays requires the precise control of hadronic uncertainties. The characteristic feature of the rare semileptonic Bs decays is a very broad kinematical range. Therefore the reliable determination of the momentum transfer dependence of the form factors turn out to be very important. Various theoretical approaches have been applied for the form-factor calculations. However, in most of such approaches the decay form factors are determined in some specific kinematic point or interval and then they are extrapolated to the whole kinematical range using some model parametrizat
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