Combined Constraints on First Generation Leptoquarks

TL;DR

This paper combines low energy precision measurements and LHC search results to constrain first-generation leptoquarks, finding that current data do not support their role in explaining the Cabibbo angle anomaly.

Contribution

It provides a comprehensive analysis of all ten first-generation leptoquark representations using both low energy and collider data, highlighting the most restrictive bounds.

Findings

Recent ATLAS di-lepton analysis sets stronger bounds than previous resonant searches.

No leptoquark representation can explain the Cabibbo angle anomaly.

Combined constraints exclude significant parameter space for first-generation leptoquarks.

Abstract

In this article we perform a combined analysis of low energy precision constraints and LHC searches for leptoquarks which couple to first generation fermions. Considering all ten leptoquark representations, five scalar and five vector ones, we study at the precision frontier the constraints from $K\to\pi\nu\nu$, $K\to\pi e^+e^-$, $K^0-\bar K^0$ and $D^0-\bar D^0$ mixing, as well as from experiments searching for parity violation (APV and QWEAK). We include LHC searches for $s$-channel single resonant production, pair production and Drell-Yan-like signatures of leptoquarks. Interestingly, we find that the recent non-resonant di-lepton analysis of ATLAS provides stronger bounds than the resonant searches recasted so far to constrain $t$-channel production of leptoquarks. Taking into account all these bounds, we observe that none of the leptoquark representations can address the so-called "Cabibbo angle anomaly" via a direct contribution to super-allowed beta decays.