From the 750 GeV Diphoton Resonance to Multilepton Excesses

TL;DR

This paper explores a model with vector-like quarks that explains the 750 GeV diphoton resonance and multilepton excesses, while also potentially addressing dark matter, by analyzing loop-induced couplings and decay channels.

Contribution

It introduces a specific vector-like quark model that accounts for the diphoton resonance, multilepton excesses, and dark matter within a unified framework.

Findings

Vector-like quarks at ~1 TeV can produce the observed diphoton signal.

The model naturally explains multilepton excesses in LHC data.

Incorporating dark matter candidates aligns with relic density observations.

Abstract

Weakly-coupled models for the 750 GeV diphoton resonance often invoke new particles carrying both color and/or electric charges to mediate loop-induced couplings of the resonance to two gluons and two photons. The new colored particles may not be stable and could decay into final states containing standard model particles. We consider an electroweak doublet of vector-like quarks (VLQs) carrying electric charges of 5/3 and 2/3, respectively, which mediate the loop-induced couplings of the 750 GeV resonance. If the VLQ has a mass at around 1 TeV, it naturally gives rise to the observed diphoton signal strength while all couplings remain perturbative up to a high scale. At the same time, if the charge-5/3 VLQ decays into final states containing top quark and W boson, it would contribute to the multilepton excesses observed in both Run 1 and Run 2 data. It is also possible to incorporate a dark matter candidate in the decay final states to explain the observed relic density.