Abstract
We study CPT and Lorentz violation in the tau-lepton sector of the Standard Model in the context of the Standard-Model Extension, described by a coefficient which is thus far unbounded by experiment. We show that any non-zero value of this coefficient implies that, for sufficiently large energies, standard-model fermions become unstable against decay due to the emission of a pair of tau-antitau leptons. We calculate the induced fermion energy-loss rate and we deduce the first limit on the Lorentz- and CPT-violating coefficient.
Highlights
Lorentz symmetry is a fundamental ingredient in both the Standard Model and general relativity
In earlier work [7] it was shown how a CPT and Lorentz violation (LV) operator in the sector of weak gauge bosons results in the possibility that at sufficiently high energy fermions that couple to these gauge bosons can emit on-shell W bosons, resulting in their decay. As such emissions should be able to occur for normally stable particles such as the proton, this opens the possibility to bound the relevant Standard-Model Extension (SME) coefficient by considering the fact that protons are present in ultrahigh-energy cosmic rays (UHECRs)
We focused on a hitherto unbounded Lorentz-violation coefficients (LVCs) in the tau sector of the Standard-Model Extension
Summary
Lorentz symmetry is a fundamental ingredient in both the Standard Model and general relativity. The SME allows us to quantify, in the most general possible way, the exactness of Lorentz and CPT symmetry in the form of observational constraints on the Lorentz-violation coefficients (LVCs) [6] Such restrictions on LV and CPTV may be used as a guide in finding the correct theory of quantum gravity. In earlier work [7] it was shown how a CPT and LV operator in the sector of weak gauge bosons results in the possibility that at sufficiently high energy fermions that couple to these gauge bosons can emit on-shell W bosons, resulting in their decay As such emissions should be able to occur for normally stable particles such as the proton, this opens the possibility to bound the relevant SME coefficient by considering the fact that protons are present in ultrahigh-energy cosmic rays (UHECRs). Observational data from UHECRs are used to produce a bound on the components of the bμ coefficient
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