Digluon Tagging using $\sqrt{s}=13$ TeV $pp$ Collisions in the ATLAS Detector

Jet substructure has played a key role in the development of two-prong taggers designed to identify Lorentz-boosted massive particles. Traditionally, these taggers have focused on Lorentz-boosted $W$, $Z$, and Higgs bosons decaying into pairs of quarks. However, there are a variety of models that predict new bosons with two-prong decays at other masses. In particular, light scalar or pseudoscalar particles ($a$ bosons) from extended Higgs sectors or axion-like particle models could result in Lorentz-boosted digluon jets ($a\rightarrow gg$). If the mass of the $a$ particle is much less than the mass of the Standard Model Higgs boson, then the two gluons will be collimated inside a single jet. This note studies the properties of digluon jets and investigates advanced techniques based on deep learning to separate them from generic quark and gluon jets.