Weak radiative decay Λb→Λγ in the heavy quark effective theory

The weak radiative decay Lambda(b) --> Lambda gamma is studied in the heavy quark effective theory treating s-quark as heavy. This rare decay is induced by the short distance electromagnetic penguins. Including corrections of the order of (1/m(Q)), we obtain the transition matrix element and the corresponding decay width. The Isgur-Wise function is evaluated in the large N-c limit and the branching ratio obtained is 1.48 x 10(-5).