LHC Signatures of $\tau$-Flavoured Vector Leptoquarks

TL;DR

This paper explores the collider signatures of vector leptoquarks with tau-flavour, analyzing their potential to explain B-meson anomalies and assessing their detectability at the LHC through various search channels.

Contribution

It provides a detailed phenomenological analysis of tau-flavoured vector leptoquarks, including global likelihood scans and LHC detection prospects, with new insights into their parameter space and experimental signatures.

Findings

Leptoquark masses constrained up to 1770 GeV by direct searches.

Missing-energy searches set bounds up to 1700 GeV, less sensitive to flavour branching ratios.

Models can potentially explain B-meson decay anomalies.

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 $\Delta_\mu$ with assignments $\left({\bf{3}}, {\bf{1}}, 2/3 \right)$ 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 $\tau$-flavoured $\Delta_\mu$, 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 $\Delta_\mu$ mass up to 1500-1770 GeV when the branching fraction of $\Delta_\mu$ 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.