LHC signatures of τ-flavoured vector leptoquarks

Abstract

Abstract We consider the phenomenological signatures of Simplified Models of Flavourful Leptoquarks, whose Beyond-the-Standard Model (SM) couplings to fermion generations occur via textures that are well motivated from a broad class of ultraviolet flavour models (which we briefly review). We place particular emphasis on the study of the vector leptoquark ∆μ with assignments (3,1, 2/3) under the SM’s gauge symmetry, SU(3)C× SU(2)L× U(1)Y, which has the tantalising possibility of explaining both $$ {\mathcal{R}}_{K^{\left(\ast \right)}} $$ R K ∗ and $$ {\mathcal{R}}_{D^{\left(\ast \right)}} $$ R D ∗ anomalies. Upon performing global likelihood scans of the leptoquark’s coupling parameter space, focusing in particular on models with tree-level couplings to a single charged lepton species, we then provide confidence intervals and benchmark points preferred by low (er)-energy flavour data. Finally, we use these constraints to further evaluate the (promising) Large Hadron Collider (LHC) detection prospects of pairs of τ-flavoured ∆μ, through their distinct (a)symmetric decay channels. Namely, we consider direct third-generation leptoquark and jets plus missing-energy searches at the LHC, which we find to be complementary. Depending on the simplified model under consideration, the direct searches constrain the ∆μ mass up to 1500-1770 GeV when the branching fraction of ∆μ is entirely to third-generation quarks (but are significantly reduced with decreased branching ratios to the third generation), whereas the missing-energy searches constrain the mass up to 1150-1700 GeV while being largely insensitive to the third-generation branching fraction.