Study of the leptonic decays of pseudoscalarB,Dand vectorB*,D*mesons and of the semileptonic

C. Albertus

¹

,

E. Hernández

²

,

J. Nieves

³

et al.

Abstract

We present results for different observables in weak decays of pseudoscalar and vector mesons with a heavy c or b 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 fV MV /fP MP = 1, a result expected in heavy quark symmetry when the heavy quark masses tend to infinity. We also analyze the semileptonic B → D and B → D * 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 |V cb | Cabbibo-KobayashiMaskawa matrix element. From the B → D semileptonic decay we get |V cb | = 0.040 ± 0.006 in perfect agreement with our previous determination based on the study of the semileptonic Λ b → Λc 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 gB * Bπ(0) = 60.5 ± 1.1 and gD * Dπ(0) = 22.1 ± 0.4. The ratio R = ( gB * Bπ(0) fB * √ MD )/( gD * Dπ(0) fD * √ MB ) = 1.105 ± 0.005 agrees with the heavy quark symmetry prediction of 1.

Semileptonic decays of heavy baryons in the relativistic quark model

“…The comparison of our model predictions with other theoretical calculations [3,26,27,28,29,30,31,32] is given in Table VII. In nonrelativistic quark models [3,26,27] form factors of the heavy baryon decays are evaluated at the single kinematic point of zero recoil and then different form factor parameterizations (pole, dipole) are used for decay rate calculations.…”

“…The relativistic three-quark model [28], Bethe-Salpeter model [29] and lightfront constituent quark model [30] assume Gaussian wave functions for heavy baryons. The authors of the recent nonrelativistic quark model [31] use for the form factor evaluations the set of variational wave functions, obtained from baryon spectra calculations without employing the quark-diquark approximation. Finally, Ref.…”

“…8 and 9. The decay rates of bottom baryons with the axial vector diquark, calculated in the heavy quark limit using expressions (31), are given in Table VI. For masses of bottom baryons and the Ω * c we used the values from Table II and for other charmed baryons we used experimental mass values [19].…”

Static properties and semileptonic decays of doubly heavy baryons in a nonrelativistic quark model

“…Thus, to evaluate the above expression we have made use of an expansion in l, introduced in Ref. [38], where second order terms in l are neglected, while all orders in | q | are kept. For instance…”

Study of semileptonic and nonleptonic decays of the B c − meson

“…For the η c we use our own theoretical result obtained with the model described in ref. [11]. In [12], obtained using the Bethe-Salpeter equation, and the ones by Kiselev [13], obtained within the three point sum rules of QCD and nonrelativistic QCD.…”