The quark-lepton portal beyond leptoquarks

TL;DR

This work investigates a quark-lepton portal that connects the Standard Model to new exotic states (LEX) through dimension-5 and dimension-6 operators involving at least one quark and one lepton. Using the Light Exotics EFT (LEX-EFT) framework, the authors systematically catalog spin-0, spin-1/2, and spin-1 LEX states, detailing CP-even and CP-odd sectors and incorporating interactions with Higgs fields and gauge field strengths. They reveal a rich spectrum of novel representations, such as SU(3) 15-plets, color sextets, and SU(2) quadruplets and quintuplets, and discuss collider production channels at the LHC, LHeC, and muon colliders, including three- and four-point vertices and diverse decay modes. A focused LHC study of color sextet LEX scalars demonstrates that single production can dominate over pair production at higher masses and provides constraints via recasts of existing SUSY searches. Overall, the paper delivers a comprehensive, redundancy-cleansed operator catalog for beyond-leptoquark states and outlines clear directions for future collider tests and UV-completions.

Abstract

We explore models where single new exotic states interact with the Standard Model through an asymmetric Standard Model portal with couplings to at least one quark and one lepton. All effective operators up to dimension six where such interactions couple the SM to spin 0 and spin 1/2 particles are written down, and the exotic states accessible through the portal are identified. We note interactions that couple the SM to new particles with exotic combinations of baryon and lepton numbers, states of higher electric charge, and particles with unusual SM charge, including states in higher-dimensional representations of both SU(3) and SU(2). Finally, we discuss the phenomenology of these interactions, including novel particle decays, and we classify some of the collider production modes for exotic states at the LHC, LHeC and muon colliders.