Physics of leptoquarks in precision experiments and at particle colliders

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.