Constraints on ∆L = 2 vector bosons with tree couplings to SM particles

Abstract

Abstract We investigate phenomenological implications of vector bosons V transforming as (1, 2, -3/2) under the standard model (SM) product gauge group SU(3) C , SU(2) L and U(1) Y . These vector bosons can couple to two SM leptons at tree-level forming dimension-4 operators. These operators dictate V to have two units of global lepton number, ∆L = 2. The operators generated conserve the global lepton number but can violate generational lepton numbers. We study constraints on the couplings Y of V to SM particles using tree-level processes such as l α − → l β + l ρ − l σ − $$ {l}_{\alpha}^{-}\to {l}_{\beta}^{+}{l}_{\rho}^{-}{l}_{\sigma}^{-} $$ , muonium and antimuonium oscillation, neutrino trident scattering, inverse muon decay, e − e + → l − l +, and also one-loop level processes such as the magnetic dipole moment of a charged lepton and l i → l j γ. Strong constraints are obtained from l α − → l β + l ρ − l σ − $$ {l}_{\alpha}^{-}\to {l}_{\beta}^{+}{l}_{\rho}^{-}{l}_{\sigma}^{-} $$ with | Y ee Y μe ∗ $$ {Y}_{ee}{Y}_{\mu e}^{\ast } $$ | < 3.29 × 10 −11 (m V /GeV)2 , ∣ Y ee Y μe ∗ ∣ $$ \mid {Y}_{ee}{Y}_{\mu e}^{\ast}\mid $$ < 3.29 × 10 −11 (m V /GeV)2 and from l i → l j γ with ∣ Y τe Y μτ ∗ ∣ $$ \mid {Y}_{\tau e}{Y}_{\mu \tau}^{\ast}\mid $$ < 3.46 × 10 −12(m V /GeV)2 , ∣ Y eτ Y τμ ∗ ∣ $$ \mid {Y}_{e\tau}{Y}_{\tau \mu}^{\ast}\mid $$ < 3.46 × 10 −12 (m V /GeV)2, respectively. Interestingly, the imaginary part of the coupling constant in our model induces CP violation, which is constrained by experimental limits on the electric dipole moment.

Keywords

• Baryon/Lepton Number Violation
• Specific BSM Phenomenology