# Hadronic $\tau$ Decays as New Physics Probes in the LHC Era

Cirigliano, Vincenzo (Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA) ; Falkowski, Adam (Laboratoire de Physique Théorique (UMR8627), CNRS, Université Paris-Sud, Université Paris-Saclay, 91405 Orsay, France) ; González-Alonso, Martín (Theoretical Physics Department, CERN, 1211 Geneva 23, Switzerland) ; Rodríguez-Sánchez, Antonio (Departament de Física Teòrica, IFIC, Universitat de València—CSIC, Apartat de Correus 22085, E-46071 València, Spain) (Department of Astronomy and Theoretical Physics, Lund University, Sölvegatan 14A, SE 223-62 Lund, Sweden)

07 June 2019

Abstract: We analyze the sensitivity of hadronic $\tau$ decays to nonstandard interactions within the model-independent framework of the standard model effective field theory. Both exclusive and inclusive decays are studied, using the latest lattice data and QCD dispersion relations. We show that there are enough theoretically clean channels to disentangle all the effective couplings contributing to these decays, with the $\tau \to \pi \pi {\nu }_{\tau }$ channel representing an unexpected powerful new physics probe. We find that the ratios of nonstandard couplings to the Fermi constant are bound at the subpercent level. These bounds are complementary to the ones from electroweak precision observables and $pp\to \tau {\nu }_{\tau }$ measurements at the LHC. The combination of $\tau$ decay and LHC data puts tighter constraints on lepton universality violation in the gauge boson-lepton vertex corrections.

Published in: Physical Review Letters 122 (2019)
Published by: APS
DOI: 10.1103/PhysRevLett.122.221801
License: CC-BY-4.0

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