Glue to light signal of a new particle

Abstract

Any new particle charged under $SU(3{)}_C$ and carrying electric charge will leave an imprint in the di-photon invariant mass spectrum as it can mediate $gg\to {\hat{I}}^3{\hat{I}}^3$ process through loops. The combination of properties of loop functions, threshold resummation and gluon pdfs can result in a peak-like feature in the di-photon invariant mass around twice the mass of a given particle even if the particle is short-lived and thus it doesn't form a narrow bound state. Using recent ATLAS analysis, we set upper limits on the combined $SU(3{)}_C$ and electric charge of new particles and indicate future prospects. We also discuss the possibility that the excess of events in the di-photon invariant mass spectrum around 750 GeV originates from loops of a particle with mass around 375 GeV.

5 pages, 8 figures, resummation of gluon exchanges near the threshold and discussion added