Variable Radius, Exclusive-k$_{T}$, and Center-of-Mass Subjet Reconstruction for Higgs($\rightarrow b\bar{b}$) Tagging in ATLAS

Many physics searches in Run 2 of the Large Hadron Collider involve boosted Higgs bosons, which decay to two $b$-quarks with a large branching ratio. The Higgs boson is reconstructed as a large-$R$ jet and the $b$-quarks are reconstructed as a pair of $b$-tagged subjets. This note documents alternative subjet techniques to reconstruct and identify the two $b$-jets from highly-boosted Higgs boson decays. New subjet tagging techniques are investigated, including the use of variable radius trackjets, exclusive-$k_{T}$ subjets, and calorimeter subjets reconstructed in the center-of-mass frame of the Higgs jet. For Higgs jets with large transverse momenta (>1 TeV), these three new techniques significantly outperform the fixed radius trackjet tagging technique currently used as the standard method in ATLAS.