LHC Signatures of $\ddot{I}„$-Flavoured Vector Leptoquarks

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 $\hat{I}{”}_{\hat{I}}¼$ with assignments $\left(3,1,2/3\right)$ under the SM's gauge symmetry, $SU(3{)}_C\times SU(2{)}_L\times U(1{)}_Y$, which has the tantalising possibility of explaining both ${\mathcal{R}}_{K^{(\star )}}$ and ${\mathcal{R}}_{D^{(\star )}}$ 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 $\ddot{I}„$-flavoured $\hat{I}{”}_{\hat{I}}¼$, 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 $\hat{I}{”}_{\hat{I}}¼$ mass up to 1500-1770 GeV when the branching fraction of $\hat{I}{”}_{\hat{I}}¼$ 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.

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