Testing Lorentz-symmetry violation via electroweak decays

Abstract

In this work we introduce CPT-odd non-minimal Lorentz-symmetry violating couplings to the electroweak sector modifying the interaction between leptons and gauge bosons. The vertex rules allow us to calculate tree-level processes modified by the presence of the novel dimension-five operators. For definitiveness, we investigate the W decay into a lepton-neutrino pair, the Z decay into pairs of charged and neutral leptons, as well as the decay of the muon. By comparing the experimental measurements on these processes to our results we are able to place upper bounds on combinations of the background 4-vectors of up to ∼ 10 −4 GeV −1 .

Limits on non-minimal Lorentz violating parameters through FCNC and LFV processes

“…Is important to highlight that our bounds in the leptonic sector are, comparing with our weakest bound, five times times more accurate than the bound reach in Ref. [19] (where ρ T SCF < 8 × 10 −7 M eV −1 ). Table III: Limits for Lorentz violation parameters from the experimental limits of the leptonic LFV sector.…”

“…As we will see, this non-diagonal terms gives us stronger bounds than the diagonal ones showed in the quark sector. Shallowly speaking, we have that after modification of the covariant derivative the Lagrangian corresponding to the leptonic sector can be written as follows [12,19]:…”

“…The above Lagrangian is a generalization of the model seen in Ref. [12,19], since in this work the flavour structure are take into account.…”

“…As can be seen in [19], we need to use the Sun Centered Frame (SCF) in order to took a better inertial frame than the earth frame. So, in the SCF the module of any vector V = (V x , V y , V z ) in the SCF are given by:…”

Lorentz-symmetry violation in the electroweak sector: scattering processes in future $e^+ \, e^-$ colliders

“…[42] by introducing two LSV 4-vectors, ρ and ξ, related to the SU (2) L and U (1) Y sectors, respectively; this scenario is similar to that analyzed in refs. [46][47][48]. As a consequence, after spontaneous symmetry breaking, new couplings of the W-and Z-bosons among themselves and the Higgs boson, as well as with the leptons, arise.…”