Experimental Considerations Motivated by the Diphoton Excess at the LHC

TL;DR

This paper explores various experimental strategies and signals related to the 750 GeV diphoton excess at the LHC, considering new particles, bound states, and unconventional photon signatures.

Contribution

It provides a comprehensive analysis of potential experimental signatures and signals for the diphoton excess, including scenarios involving new particles, bound states, and long-lived particles.

Findings

Possible signals include t' decays, quirks, and hidden glueballs.

Unusual photon signatures such as overlapping photons or conversions.

Detection strategies for long-lived particles decaying to photon pairs.

Abstract

We consider the immediate or near-term experimental opportunities offered by some scenarios that could explain the new diphoton excess at the LHC. If the excess is due to a new particle $X_s$ at 750 GeV, additional new particles are required, providing further signals. If connected with naturalness, the $X_s$ may be produced in top partner decays. Then a $t'\bar t'$ signal, with $t'\to t X_s$ and $X_s\to gg$ dominantly, might be discovered by reinterpreting 13 TeV SUSY searches in multijet events with low MET and/or a lepton. If $X_s$ is a bound state of quirks, the signal events may be accompanied by an unusual number of soft tracks or soft jets. Other resonances including dilepton and photon+jet as well as dijet may lie at or above this mass, and signatures of hidden glueballs might also be observable. If the "photons" in the excess are actually long-lived particles decaying to photon pairs or to electron pairs, there are opportunities for detecting overlapping photons and/or unusual patterns of apparent photon-conversions in either $X_s$ or 125 GeV Higgs decays. There is also the possibility of events with a hard "photon" recoiling against a narrow isolated HCAL-only "jet", which, after the jet's energy is corrected for its electromagnetic origin, would show a peak at 750 GeV.