Study of semileptonic decays of B mesons to charmed baryons

Using data collected by the CLEO II detector at a center-of-mass energy on or near the {Upsilon}(4S) resonance, we have determined the 90{percent} confidence level upper limit B({bar B}{r_arrow}{Lambda}{sub c}{sup +}e{sup {minus}}X)/B{bold (}{bar B}{r_arrow}({Lambda}{sub c}{sup +} or {bar {Lambda}}{sub c}{sup {minus}})X{bold )}{lt}0.05 for electrons with momentum above 0.6GeV/c. We have also obtained the limit B(B{sup {minus}}{r_arrow}{Lambda}{sub c}{sup +}{bar p}e{sup {minus}}{bar {nu}}{sub e})/B({bar B}{r_arrow}{Lambda}{sub c}{sup +}{bar p}X){lt}0.04 at the 90{percent} confidence level and measured the ratio B({bar B}{r_arrow}{Lambda}{sub c}{sup +}{bar p}X)/B{bold (}{bar B}{r_arrow}({Lambda}{sub c}{sup +} or {bar {Lambda}}{sub c}{sup {minus}})X{bold )}=0.57{plus_minus}0.05{plus_minus}0.05. {copyright} {ital 1998} {ital The American Physical Society}