Measuring R(D()) for B → ‾D()τν_τ using Semileptonic Tags and Tau Decays to Hadrons

Author: Chao, Daniel Shuteh

Year: 2018

Degree: Dissertation (Ph.D.)

Advisor: Porter, Frank C.

Committee Members: Porter, Frank C.; Hitlin, David G.; Carroll, Sean M.; Yue, Yisong

Option: Physics; Computer Science

Abstract

We perform a measurement of R(D^(*)) for B → D(*)τν_τ using semileptonic tagging and τ decays to hadrons on the 429 fb^-1 of data that BABAR collected at the Υ(4S) resonance. This is the first measurement of R(D^(*)) using the specied reconstruction channels. Candidate selection was performed with supervised learning, where the training labels were obtained by solving an instance of subgraph isomorphism. The signal extraction was performed by solving an optimization problem whose objective function required the evaluation of kernel density estimates that were accelerated by a branch-and-bound algorithm as well as with a GPU. The training data for the density estimates were themselves the output of two classier scores. We present a 68% and 95% confidence regions of R(D^(*)), which do not show enough evidence to reject the standard model prediction.

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