Semileptonic {Lambda}{sub b} decay to excited {Lambda}{sub c} baryons at order {Lambda}{sub QCD}/m{sub Q}

Exclusive semileptonic {Lambda}{sub b} decays to excited charmed {Lambda}{sub c} baryons are investigated at order {Lambda}{sub QCD}/m{sub Q} in the heavy quark effective theory. The differential decay rates are analyzed for the J{sup {pi}}=1/2{sup {minus}} {Lambda}{sub c}(2593) and the J{sup {pi}}=3/2{sup {minus}} {Lambda}{sub c}(2625). They receive 1/m{sub c,b} corrections at zero recoil that are determined by mass splittings and the leading order Isgur-Wise function. With some assumptions, we find that the branching fraction for {Lambda}{sub b} decays to these states is 2.5{endash}3.3{percent}. The decay rate to the helicity {plus_minus}3/2 states, which vanishes for m{sub Q}{r_arrow}{infinity}, remains small at order {Lambda}{sub QCD}/m{sub Q} since 1/m{sub c} corrections do not contribute. Matrix elements of weak currents between a {Lambda}{sub b} and other excited {Lambda}{sub c} states are analyzed at zero-recoil to order {Lambda}{sub QCD}/m{sub Q}. Applications to baryonic heavy quark sum rules are explored. {copyright} {ital 1998} {ital The American Physical Society}