A search for the decay B{+-} {yields} a{sub 0}{sup {+-}}{pi}{sup 0} with the a{sub 0}{sup +} decaying to an {eta} and a {pi}{sup +} was carried out at the Stanford Linear Accelerator Center using the BABAR detector coupled with the PEP-II collider. The analysis used a data sample comprised of approximately 252 million B{bar B} pairs collected at the {Upsilon}(4S) resonance. No signal was observed and a 90% confidence level upper limit on the branching fraction was set at 1.32 x 10{sup -6}.

This thesis presents a search for the rare B meson decay B -> pi ll− (l=e or mu) using 428 fb−1 of data collected at the Upsilon(4S) resonance by the BaBar detector at the PEP-II asymmetric energy ee− storage rings located located at SLAC National Accelerator Laboratory in Menlo Park, California. Four exclusive modes are studied: B+ -> pi+ e+e−, B+ -> pi+ mu+mu−, B0 -> pi0 e+e−, and B0 -> pi0 mu+mu−. Branching fraction upper limits at the 90% confidence level are presented for the exclusive modes B+ -> pi+ mu+mu− and B0 -> pi0 mu+mu−, and the combined mode B -> pi mu+mu−.

The authors have performed a search for the flavor-changing neutral-current decays B →?ll−, where l+l− is either e+e− or?+?−, using a sample of 230 million?(4S) → B{bar B} decays collected with the BABAR detector. They observe no evidence of a signal and measure the upper limit on the isospin-averaged branching fraction to be?(B →?l+l−)

This thesis describes a search for the rare radiative decay of a B meson to two photons. where the charged congugate mode is implied throughout. These decays are highly suppressed in the Standard Model where the branching fraction is expected to be of order 10^-8. In some new physics scenarios this could be enhanced by up to an order of magnitude to 10^-7. Therefore an observation of a significant signal above the Standard Model prediction could be a sign of new physics. The search for this rare decay was performed using the data collected with the BaBar detector at the SLAC National Accelerator Laboratory PEP-II storage ring operating at the Upsilon(4S) resonance. The analysis uses a dataset with an integrated luminosity of 425.7 fb-1 corresponding to 467 million BB pairs. A signal yield of 21.3 +12.8 -11.8 events with a significance of 1.88 sigma was measured using an unbinned extended maximum likelihood fit. An upper limit on the branching fraction is set at the 90% confidence level of less than 3.2 times 10^-7. This is about two times more stringent than the best upper limit of less than 6.2 times 10^-7 published by the Belle collaboration.