Charmless exclusive baryonic B decays -: art. no. 014020

We present a systematical study of two-body and three-body charmless baryonic B decays. The branching ratios for two-body modes are in general very small, typically less than 10(-6), except that B(B--->p (Delta) over bar (--))similar to1x10(-6). In general, (B) over bar -->N (Delta) over bar >(B) over bar -->N (N) over bar due to the large coupling constant for Sigma(b)-->BDelta. For three-body modes we focus on octet baryon final states. The leading three-dominated modes are (B) over bar (0)-->p (n) over bar pi(-)(rho(-)), n (p) over bar pi(+)(rho(+)) with a branching ratio of order 3x10(-6) for (B) over bar (0)-->p (n) over bar pi(-) and 8x10(-6) for (B) over bar (0)-->p (n) over bar rho(-). The penguin-dominated decays with strangeness in the meson, e.g., B--->p (p) over barK(-()*()) and (B) over bar (0)-->p (n) over barK(-()*()), n (n) over bar(K) over bar (0()*()), have appreciable rates and the N (N) over bar mass spectrum peaks at low mass. The penguin-dominated modes containing a strange baryon, e.g., (B) over bar (0)-->Sigma(0)(p) over bar pi(+), Sigma(-)(n) over bar pi(+), have branching ratios of the order of (1-4)x10(-6). In contrast, the decay rate of (B) over bar (0)-->Lambda(p) over bar pi(+) is smaller. We explain why some of the charmless three-body final states in which baryon-antibaryon pair production is accompanied by a meson have a larger rate than their two-body counterparts: either the pole diagrams for the former have an antitriplet bottom baryon intermediate state, which has a large coupling to the B meson and the nucleon, or they are dominated by the factorizable external W-emission process.