Models of LHC Diphoton Excesses Valid up to the Planck scale

TL;DR

This paper explores models explaining the 750 GeV diphoton excess at the LHC, focusing on scalar and vector-like fermion scenarios that remain valid up to the Planck scale, with implications for future collider searches.

Contribution

It systematically analyzes vacuum stability and perturbativity constraints for models with new scalars or fermions explaining the diphoton excess, identifying viable models up to the Planck scale.

Findings

Few scalar diquark and dilepton models fit the data without conflicting bounds.

Allowed fermion models depend on scalar or pseudoscalar couplings, with more fermions increasing viability.

Predicted scalar particle masses could be tested at future lepton colliders.

Abstract

We discuss a possibility to explain the LHC diphoton excesses at $750$GeV by the new scalar $X$ that couples to the gauge bosons through the loop of new massive particles with Standard Model charges. We assume that the new particles decay into the Standard Model particles at the tree level. We systematically examine the models that preserve the vacuum stability and the perturbativity up to the Planck scale. When we take scalars for the new particles, we find that only a few diquark and dilepton models can explain the observed diphoton cross section without conflicting the experimental mass bounds. When we take vector-like fermions for the new particles, we find rather different situations depending on whether their couplings to $X$ are scalar or pseudoscalar type. In the former case, a few models are allowed if we introduce only one species of fermions. The more fermions we introduce, the more models are allowed. In the later case, the most of the models are allowed because of the large coupling between $X$ and photon. It is interesting that the allowed mass regions of the scalar particles might be reached by the next lepton colliders.