Constraints on 750 GeV colorless Q-onia from running couplings

TL;DR

This paper proposes a composite model where a 750 GeV diphoton excess is explained by bound states of vector-like fermions charged under a new confining force, fitting the data within a Coulomb approximation and predicting specific hypercharge ranges.

Contribution

It introduces a novel composite model with electroweak doublet fermions forming Q-onia, fitting the diphoton excess without strong coupling effects up to 30 TeV.

Findings

Allowed hypercharge ranges for different N_TC values.

Consistency with observed diphoton excess.

Predicted decay into Higgs and Z-boson as a signature.

Abstract

We present yet another composite model explaining the relatively broad peak in the diphoton invariant mass distribution around 750 GeV recently observed at the LHC experiments. We consider the excess originates in bound states of vector-like fermions Q transforming under the electroweak group (but not QCD) of the standard model and which are also charged under a new SU(N_{TC}) QCD-like confining force. Since the new uncolored fields transform as SU(2) doublets they can acquire a mass through Yukawa interactions with the electroweak Higgs doublet, as quarks and leptons. We parametrize the Q-onium bound state using the Coulomb approximation and give a numerical fit to the diphoton excess consistent with no strong coupling effects up to about 30 TeV, which is the energy scale for next generation colliders. The range of allowed hypercharge Y_Q is given by 2.26 \leq Y_Q \leq 2.53 for N_{\rm TC} =2 and 2.17 \leq Y_Q \leq 2.31 for N_{\rm TC} = 3. The smoking gun for the model would be the discovery of Q-onia decaying into Higgs and Z-boson.