Weak decays in the light-front quark model

Abstract

We study the form factors of heavy-to-heavy and heavy-to-light weak decays using the light-front relativistic quark model. For the heavy-to-heavy B~D ' semileptonic decays we calculate the corresponding Isgur-Wise function for the whole kinematic region. For the heavy-to-light B -+ P and B~V semileptonic decays we calculate the form factors at q = 0; in particular, we have derived the dependence of the form factors on the 6-quark mass in the m&~oo limit. This dependence cannot be produced by extrapolating the scaling behavior of the form factors at q "using the single-pole assumption. This shows that the q dependence of the form factors in regions far away from the zero recoil could be much more complicated than that predicted by the single-pole assumption.

Covariant light-front approach fors-wave andp-wave mesons: Its application to decay constants and form factors

“…For reader's convenience, the explicit forms of these form factors are summarized in Appendix B. Note that the vector form factor V (q 2 = 0) = −(M ′ + M ′′ )g(q 2 = 0) is consistent with that in [7,41] 23) and see that the second term on the right-hand side is needed when considering the q ⊥ → 0 limit of the p ′ · q ⊥ /q 2 term in the integrand of g(q 2 ), while O(x 2 2 q 2 ) terms in the above equation vanish in the same limit. We perform the angular integration in the p ′ ⊥ plane before taking the q 2 → 0 limit.…”

The spin-symmetry of the quark model

“…[2], it has been pointed out that the scaling behavior of the meson decay constant f M in the heavy-quark limit imposes a constraint on the orbital wave function. The Gaussian wave function in (12) is shown to satisfy the scaling law 1/ √ m Q of f M in the heavy m Q limit.…”

“…[2,5,6]. In the relativistic quark model, the wave function for the ground state meson M(Qq) is given by…”

“…In our recent paper using the relativistic quark model [2], we found that the breaking of the spin symmetry among hadronic form factors is small even for heavy-to-light quark decays. In this paper, we show explicitly, using the same model, that there is something other than the mass effect that suppresses the breaking of the spin symmetry.…”

“…(2). We use the relativistic quark model formulated in the infinite momentum frame (or equivalently, the light-front quark model) [2,4,5,6].…”