Physics of leptoquarks in precision experiments and at particle colliders

TL;DR

This review comprehensively discusses the phenomenology, constraints, and collider searches for light leptoquarks, emphasizing their implications for precision experiments and collider physics within models that preserve proton stability.

Contribution

It provides a broad, model-independent analysis of leptoquark effects, including recent collider predictions and constraints from low-energy precision measurements.

Findings

Leptoquarks are constrained by various low-energy observables.

Current collider searches set bounds on leptoquark masses and couplings.

Next-to-leading order predictions improve collider search accuracy.

Abstract

We present a comprehensive review of physics effects generated by leptoquarks (LQs), i.e., hypothetical particles that can turn quarks into leptons and vice versa, of either scalar or vector nature. These considerations include discussion of possible completions of the Standard Model that contain LQ fields. The main focus of the review is on those LQ scenarios that are not problematic with regard to proton stability. We accordingly concentrate on the phenomenology of light leptoquarks that is relevant for precision experiments and particle colliders. Important constraints on LQ interactions with matter are derived from precision low-energy observables such as electric dipole moments, (g-2) of charged leptons, atomic parity violation, neutral meson mixing, Kaon, B, and D meson decays, etc. We provide a general analysis of indirect constraints on the strength of LQ interactions with the quarks and leptons to make statements that are as model independent as possible. We address complementary constraints that originate from electroweak precision measurements, top, and Higgs physics. The Higgs physics analysis we present covers not only the most recent but also expected results from the Large Hadron Collider (LHC). We finally discuss direct LQ searches. Current experimental situation is summarized and self-consistency of assumptions that go into existing accelerator-based searches is discussed. A progress in making next-to-leading order predictions for both pair and single LQ productions at colliders is also outlined.