Semi-Leptonic Decays of Λ_c and Λ_b Baryons involving Heavy to Light Transitions and the determination of V_{ub}

Abstract

We calculate the semi-leptonic decays of $Λ_c$ and $Λ_b$ 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 $Λ_c \rightarrow Λπ^{+}$ and $Λ_c \rightarrow Σ^{+} π^{0 }$ to obtain information on the form factors in the $c \rightarrow s $ transition. This form factor informations is used to study the semi-leptonic decay $Λ_c \rightarrow Λl ν$. Using SU(3) symmetry and HQET it is shown how a knowledge of form factors in $Λ_c \rightarrow Λl ν$ can be applied to $Λ_b \rightarrow p l ν$ decay and used to measure $|V_{ub}/V_{cs}|^{2} $.