Semi-Leptonic Decays of \Lambda_c and \Lambda_b Baryons involving Heavy to Light Transitions and the determination of V_{ub}

Abstract

We calculate the semi-leptonic decays of ${\Lambda }_c$ and ${\Lambda }_b$ baryons which involve transitions of a heavy quark to a light quark. In a previous work we used data on the Cabibbo favoured non-leptonic decays of charmed baryons ${\Lambda }_c\to \Lambda {\pi }^{+}$ and ${\Lambda }_c\to {\Sigma }^{+}{\pi }^0$ to obtain information on the form factors in the $c\to s$ transition. This form factor informations is used to study the semi-leptonic decay ${\Lambda }_c\to \Lambda l\nu$. Using SU(3) symmetry and HQET it is shown how a knowledge of form factors in ${\Lambda }_c\to \Lambda l\nu$ can be applied to ${\Lambda }_b\to pl\nu$ decay and used to measure $|V_{ub}/V_{cs}{|}^2$.

Comments: 9 pages, Latex, 5 figures available on request