Jet activity as a probe of high-mass resonance production

We explore the method of using the measured jet activity associated with a high mass resonance state to determine the corresponding production modes. To demonstrate the potential of the approach, we consider the case of a resonance of mass $M_R$ decaying to a diphoton final state. We perform a Monte Carlo study, considering three mass points $M_R=0.75,\,1.5\,,2.5$ TeV, and show that the $\gamma\gamma$, $WW$, $gg$ and light and heavy $q\overline{q}$ initiated cases lead to distinct predictions for the jet multiplicity distributions. As an example, we apply this result to the ATLAS search for resonances in diphoton events, using the 2015 data set of $3.2\,{\rm fb}^{-1}$ at $\sqrt{s}=13$ TeV. Taking the spin-0 selection, we demonstrate that a dominantly $gg$-initiated signal hypothesis is mildly disfavoured, while the $\gamma\gamma$ and light quark cases give good descriptions within the limited statistics, and a dominantly $WW$-initiated hypothesis is found to be in strong tension with the data. We also comment on the $b\overline{b}$ initial state, which can already be constrained by the measured $b$-jet multiplicity. Finally, we present expected exclusion limits with integrated luminosity, and demonstrate that with just a few 10's of ${\rm fb}^{-1}$ we can expect to constrain the production modes of such a resonance.