Abstract
The effective-Lagrangian description of Lorentz-invariance violation provided by the so-called Standard-Model Extension covers all the sectors of the Standard Model, allowing for model-independent studies of high-energy phenomena that might leave traces at relatively-low energies. In this context, the quantification of the large set of parameters characterizing Lorentz-violating effects is well motivated. In the present work, effects from the Lorentz-nonconserving Yukawa sector on the electromagnetic moments of charged leptons are calculated, estimated, and discussed. Following a perturbative approach, explicit expressions of leading contributions are derived and upper bounds on Lorentz violation are estimated from current data on electromagnetic moments. Scenarios regarding the coefficients of Lorentz violation are considered. In a scenario of two-point insertions preserving lepton flavor, the bound on the electron electric dipole moment yields limits as stringent as $10^{-28}$, whereas muon and tau-lepton electromagnetic moments determine bounds as restrictive as $10^{-14}$ and $10^{-6}$, respectively. Another scenario, defined by the assumption that Lorentz-violating Yukawa couplings are Hermitian, leads to less stringent bounds, provided by the muon anomalous magnetic moment, which turn out to be as restrictive as $10^{-14}$.
Highlights
It has been half a century since its formulation [1,2,3], and yet the Standard Model (SM) remains our best theoretical description of fundamental physics [4]
The present investigation has been performed in the context established by the Lorentz- and CPT-violating Standard Model extension, an effective field theory which sets a quite general framework to quantify, at relatively low energies, the effects to be expected from a higherenergy formulation incorporating violation of Lorentz invariance
While this model of new physics extends every sector of the Standard Model, by the inclusion of both renormalizable and nonrenormalizable Lagrangian terms, our discussion has been restricted to couplings occurring in the Yukawa sector of the renormalizable part of the Standard Model extension
Summary
It has been half a century since its formulation [1,2,3], and yet the Standard Model (SM) remains our best theoretical description of fundamental physics [4]. Since the resulting contributions involve a plethora of Lorentz-violation parameters, assumptions aiming at the reduction of the number of SME quantities are made, for which two scenarios are considered In one of these scenarios, some SME parameters introduced by lepton-flavor-nonconserving two-point insertions are assumed to be quite small, being disregarded and leaving appropriate conditions to bound Lorentz-violation coefficients to be as small as 10−27, from the electric dipole moment of the electron, and limits as restrictive as 10−14 and 10−5 if constraints on the muon and the tau-lepton electromagnetic moments, respectively, are taken into account.
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