B mesons are unique among well-established non-quarkonium mesons in their ability to decay into baryons. Baryonic B decays offer a wide range of interesting areas of study: they can be used to test our theoretical understanding of rare decay processes involving baryons, search for direct CP violation and study low-energy QCD. This thesis presents measurements of branching fractions and a study of the decay dynamics of the charmless three-body decays of B meson into p{bar p}h final states, where h = {pi}{sup +}, K{sup +}, K{sub S}{sup 0}, K*{sup 0} or K*{sup +}. With a sample of 232 million {Upsilon}(4S) {yields} B{bar B} events collected with the BaBar detector, we report the first observation of the B {yields} p{bar p}K*{sup 0} decay, and provide improved measurements of branching fractions of the other modes. The distribution of the three final-state particles is of particular interest since it provides dynamical information on the possible presence of exotic intermediate states such as the hypothetical pentaquark states {Theta}*{sup ++} and {Theta}{sup +}in the m{sub pK{sup +}} and m{sub pK{sub S}{sup 0}} spectra, respectively, or glueball states (such as the tensor glueball f{sub J}(2220)) in the m{sub p{bar p}} spectrum. No evidence for exotic states is found and upper limits on the branching fractions are set. An enhancement at low p{bar p} mass is observed in all the B {yields} p{bar p}h modes, and its shape is compared between the decay modes and with the shape of the time-like proton form factor. A Dalitz plot asymmetry in B {yields} p{bar p}K{sup +} mode suggests dominance of the penguin amplitude in this decay and disfavors the possibility that the low mass p{bar p} enhancement originates from the presence of a resonance below threshold (such as the recently seen baryonium candidate at 1835 MeV/c{sup 2}). We also identify decays of the type B {yields} X{sub c{bar c}}h {yields} p{bar p}h, where h = K{sup +}, K{sub S}{sup 0}, K*{sup 0} or K*{sup +}, and X{sub c{bar c}} = {eta}{sub c} or J/{psi}. In particular, we report on the evidence of the B {yields} {eta}{sub c}K*{sup +} decay and provide a measurement of the width of {eta}{sub c}.

A study of B-meson decays to final states with a single charm baryon is presented based on data recorded by the BABAR detector at the Stanford Linear Accelerator Center. Although the B meson is the lightest bottom-flavored meson, it is heavy enough to decay to a baryon made of three quarks and an antibaryon made of three antiquarks. By studying the baryonic weak decays of the B meson, we can investigate baryon production mechanisms in heavy meson decays. In particular, we measure the rates of the decays B- → [Lambda]+c$\bar{p}$[pi]- and $\bar{B}$0 → [Lambda]+c$\bar{p}$. Comparing these rates, we confirm an observed trend in baryonic B decays that the decay with the lower energy release, B- → [Lambda]+c$\bar{p}$[pi]-, is favored over $\bar{B}$0 → [Lambda]+c$\bar{p}$. The dynamics of the baryon-antibaryon ([Lambda]+c$\bar{p}$) system in the three-body decay also provide insight into baryon-antibaryon production mechanisms. The B- → [Lambda]+c$\bar{p}$[pi]- system is a laboratory for searches for excited #c baryon states; we observe the resonant decays B- → [Sigma]c(2455) 0$\bar{p}$ and B- → [Sigma]c(2800) 0$\bar{p}$. This is the first observation of the decay B- → [Sigma]c(2800) 0$\bar{p}$; however, the mass of the observed #c(2800)0 state is inconsistent with previous measurements. Finally, we examine the angular distribution of the B- → [Sigma]c(2455) 0$\bar{p}$ decays and measure the spin of the B- → [Sigma]c(2455) 0$\bar{p}$ baryon to be J = 1/2, as predicted by the quark model.

We have studied two-body charmless hadronic decays of B mesons into the final states??, K?, and KK. Using 3.3 million B{bar B} pairs collected with the CLEO-II detector, we have made the first observation of the decays B° → K?−, B+ → K°?+, and the sum of B+ →?+?° and B+ → K+?° decays (an average over charge-conjugate states is always implied). We place upper limits on branching fractions for the remaining decay modes.