A Search for the Rare Decay B->tau+tau- at the BaBar Experiment

Abstract

The Standard Model of particle physics predicts that the branching ratio for the rare decay B{sup 0} {yields} {tau}{sup +}{tau}{sup -} is 3.1 x 10{sup -8}, though untested models which could supersede it predict large enhancements. This dissertation describes the search for this rare decay in 210.4 fb{sup -1} of B{sup 0}{bar B}{sup 0} data collected at the {Upsilon}(4S) resonance in the Babar detector at the Stanford Linear Accelerator Center. In the analysis, one neutral B meson is fully reconstructed in a hadronic mode and recoil events which are consistent with each tau decaying in a mode {tau} {yields} {pi}{nu}, {rho}{nu}, or l{nu}{bar {nu}} are selected. There is no evidence for signal. The result is consistent with a downward fluctuation by 1.1 statistical standard deviations of the expected Standard Model background. Taking the expected background, the number of observed events and the expected statistical and systematic errors into account yields 2.7 x 10{sup -3} as the upper limit for B{sup 0} {yields} {tau}{sup +}{tau}{sup -} at the 90% confidence level.

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