Squarkonium, diquarkonium and octetonium at the LHC and their di-photon decays

TL;DR

This paper investigates the production and di-photon decay of exotic scalar onia at the LHC, finding that diquarkonium and octetonium could explain the di-photon excess with distinctive collider signatures.

Contribution

It systematically analyzes the di-photon decay signals of various color exotic scalar onia, highlighting the potential of diquarkonium and octetonium to account for the excess.

Findings

Diquarkonium and octetonium predictions are around 10 fb, larger than stoponium.

Stoponium predictions are too small to explain the excess.

Color enhancement leads to large production but faces direct search constraints.

Abstract

Motivated by the recent di-photon excess by both ATLAS and CMS collaborations at the LHC, we systematically investigate the production and di-photon decay of onia formed by pair of all possible color exotic scalars in minimal extension. When such scalar massive meta-stable colored and charged (MMCC) particles are produced in pair near threshold, $\eta$ onium can be formed and decay into di-photon through annihilation as $pp\to \eta \to \gamma\gamma$. Squarkonium is formed by meta-stable squarks in supersymmetric models such as stoponium. Diquarkonium is formed by meta-stable color sextet diquarks which may be realized in the Pati-Salam model. Octetonium is formed by color octet scalars bosons as in the Manohar-Wise model. Stoponium prediction is much smaller than the required signal to account for the di-photon excess. Due to the enhancement factor from color and electric charge, predictions of diquarkonium and octetonium are of $\cal O$(10 fb) which are significantly greater than the stoponium prediction. Since the color enhancement also results in large production at the colliders, such light color exotic states of $\cal O$(375 GeV) suffer from severe direct search constraints. On the other hand, if their dominant decay mode involve top quark, they may be buried in the $t\bar{t}$ plus jets samples and can potentially be searched via $t+j$ resonance.