On the 1/m^2 corrections to the form-factors in /\_b -> /\_c semileptonic decays

Abstract

Model-independent bounds are presented for the form-factors describing the semileptonic decay ${\Lambda }_b\to {\Lambda }_{c}e{\bar{\nu }}_e$ at the end-point of the lepton energy spectrum. For the axial-vector form-factor $f_1^A(1)$ we obtain $f_1^A(1)\le 0.960÷0.935$, where the uncertainty arises from the value of ${\mu }_{\pi }^2$, the average kinetic energy of the $b$ quark inside of the ${\Lambda }_b$ baryon. A bound is given on the forward matrix element of the axial current in a ${\Lambda }_b$ baryon which is relevant for the inclusive semileptonic decays of the polarized ${\Lambda }_b$ decays.

Comments: LaTeX, 8 pages, MZ-TH/94-16