Models of 750 GeV quarkonium and the LHC excesses

TL;DR

This paper proposes models involving a vector-like quark that forms a 750 GeV bound state, explaining LHC diphoton excesses and related signals, while also incorporating dark matter candidates and suggesting monojet searches as key probes.

Contribution

It introduces a UV-complete model with a vector-like quark and additional particles that explain multiple LHC excesses and include a dark matter candidate.

Findings

A hypercharge of -4/3 fits the diphoton signal.

An SU(2) doublet quark around 600 GeV can explain multiple excesses.

Dark matter relic density is influenced by coannihilation.

Abstract

We investigate models involving a vector-like quark X, which forms a 750 GeV bound state and reproduces the observed diphoton signals at the LHC, in connection with other excesses in the LHC data. An exotic hypercharge of -4/3 is required to fit the signal cross section, which indicates that there is additional particle(s) that mediates the decay of X in the full theory. We find that, introducing an SU(2) doublet vector-like quark of mass around 600 GeV in our UV-complete framework can accommodate not only the diphoton but also the on-Z excess (and potentially a slight excess in the monojet events). Our models also include a dark matter candidate. The most useful way to probe the models at the LHC is via monojet searches. The relic dark matter density is largely determined by coannihilation effects, and indirect detection of dark matter annihilation signals is the alternative and complementary probe of our models.