Higgs Stability and the 750 GeV Diphoton Excess

TL;DR

This paper explores how a potential 750 GeV particle could influence Higgs stability, naturalness, and inflation, proposing a minimal extension to the Standard Model with new particles that stabilize the vacuum.

Contribution

It introduces a minimal model adding a pseudoscalar and vector-like fermion to stabilize the Higgs vacuum without high-energy new physics, and discusses inflation via UV-modified gravity.

Findings

A 750 GeV particle can stabilize the electroweak vacuum.

The minimal model avoids unnatural Higgs mass contributions.

Inflation can be achieved through UV modifications of gravity.

Abstract

We study the implications of a possible unstable particle with mass $M_X<$ TeV for the Higgs stability, naturalness and inflation. We pay particular attention to the case $M_X\approx$ 750 GeV, suggested by recent results of ATLAS and CMS on diphoton final states, and work within the minimal model: we add to the Standard Model field content a pseudoscalar and a vector-like fermion carrying both color and electric charge. This can stabilize the electroweak vacuum without invoking new physics at very high energies, which would give an unnaturally large contribution to the Higgs mass. We also show that inflation can be obtained via a UV modification of General Relativity.