WEAK MATRIX ELEMENTS AND |V_cb| IN HQEFT

Abstract

The heavy quark effective field theory (HQEFT) containing both effective 'quark fields' and 'antiquark fields' is investigated in detail. By integrating out (but not neglecting) the effective antiquark fields, we present a new formulation of effective theory which differs from the usual heavy quark effective theory (HQET) and exhibits valuable features because of the inclusion of the contributions from the antiquark fields. Matrix elements of vector and axial vector heavy quark currents between pseudoscalar and vector mesons containing a heavy quark (b or c) are then evaluated systematically up to the order of 1/m 2 Q and parameterized by a set of universal form factors. With a consistent normalization condition between the effective heavy hadron states, the form factors at zero recoil are related to the ground state meson masses, which enables us to estimate the values of form factors at zero recoil. In particular, the Luke's theorem comes out automatically in the new formulation of HQEFT without the need of imposing the equation of motion iv ·DQ + v = 0. Consequently, the differential decay rates of both B → D * lν and B → Dlν do not receive 1/m Q order corrections at zero recoil, which is not the case in the usual HQET. Thus we quote that the Cabibbo-Kobayashi-Maskawa matrix element |V cb | can nicely be extracted from either of these two exclusive semileptonic decays at the order of 1/m 2 Q . Our estimates for |V cb | are presented.

Lifetime Difference and Endpoint Effect in the Inclusive Bottom Hadron Decays

“…The resulting central values for charm counting n c (B 0 ) seems slightly larger than the experimental data though it is still consistent within the errors. The resulting prediction for the CKM matrix element |V cb | agrees well with the one extracted from the exclusive decays [12].…”

Semileptonic B Decays Into Excited Charmed Mesons $(D_1,d^*_2)$ in Hqeft

“…In the framework of HQEFT (its main formulation is presented in Appendix A, we can in general introduce an effective heavy hadron state |H v for the witness of exhibiting manifestly the spin-flavor symmetry [6][7][8]. It is related to the hadron state |H in the full theory via…”

“…Correspondingly, the heavy quark current turns out to be [6][7][8][9] [18] 0.56 ± 0.13 ± 0.08 ± 0.04 0.8 Br(ALEPH) [19] 0.74 ± 0.16 0.2 Table 2. Branching ratios (in %) at some values of η …”

Heavy to light meson exclusive semileptonic decays in effective field theory of heavy quarks

“…It is related to the heavy meson state M in Eqs. (2.1) and (2.2) by the normalization of the hadronic matrix elements [27]:…”

“…In particular, in Refs. [24,25] the B → π(ρ)lν decays are investigated within the framework of heavy quark effective field theory (HQEFT) [26][27][28], and the relevant form factors are calculated at the leading order of heavy quark expansion, using which |V ub | is extracted. This paper will provide a more general discussion on exclusive heavy to light decays within the framework of effective theory.…”