The Leptoquark Hunter's Guide: Large Coupling

TL;DR

This paper expands leptoquark search strategies to include large couplings, exploring single production and t-channel exchange, and updates bounds from LHC and atomic parity violation, highlighting future LHC potential.

Contribution

It introduces a comprehensive search framework for large-coupling leptoquarks, including new channels and updated experimental bounds, enhancing the exploration of their role in B physics anomalies.

Findings

Current limits do not exclude leptoquarks as an explanation for B anomalies.

High luminosity LHC can probe the most interesting parameter space.

Different search channels are complementary in covering parameter space.

Abstract

Leptoquarks have recently received much attention especially because they may provide an explanation to the $R_{D^{(*)}}$ and $R_{K^{(*)}}$ anomalies in rare $B$ meson decays. In a previous paper we proposed a systematic search strategy for all possible leptoquark flavors by focusing on leptoquark pair production. In this paper, we extend this strategy to large (order unity) leptoquark couplings which offer new search opportunities: single leptoquark production and $t$-channel leptoquark exchange with dilepton final states. We discuss the unique features of the different search channels and show that they cover complementary regions of parameter space. We collect and update all currently available bounds for the different flavor final states from LHC searches and from atomic parity violation measurements. As an application of our analysis, we find that current limits do not exclude the leptoquark explanation of the $B$ physics anomalies but that the high luminosity run of the LHC will reach the most interesting parameter space.