Search For The Rare Decay B To Pi L L

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−.