Complete framework for tau polarimetry in B →D<SUP>(*)</SUP>τ ν decays

Asadi, Pouya; Hallin, Anna; Martin Camalich, Jorge; Shih, David; Westhoff, Susanne
Bibliographical reference

Physical Review D

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The meson decays B →D τ ν and B →D*τ ν are sensitive probes of the b →c τ ν transition. In this work, we present a complete framework to obtain the maximum information on the physics of B →D(*)τ ν with polarized τ leptons and unpolarized D(*) mesons. Focusing on the hadronic decays τ →π ν and τ →ρ ν , we show how to extract seven τ asymmetries from a fully differential analysis of the final-state kinematics. At Belle II with 50 ab-1 of data, these asymmetries could potentially be measured with percent-level statistical uncertainty. This would open a new window into possible new physics contributions in b →c τ ν and would allow us to decipher its Lorentz and gauge structure.