The status of Missing Mass Calculator for Higgs boson mass estimation in the ATLAS Hττ analysis

The reconstruction of the Higgs boson mass represents one of the key challenges in the H → ττ analysis, where instant τ-lepton decays contain non-detectable neutrinos. Precise mass reconstruction is a prerequisite for reasonable separation between the signal (alike gg→ H→ττ) and background (e.g. Z→ττ) processes. The ATLAS collaboration has developed an advanced technique for the Higgs boson mass reconstruction (Missing Mass Calculator, MMC) which proved its efficiency and resolution in Run 1 and first Run 2 analyses at the LHC. MMC relies on knowledge of the probability of the decay topology, the missing transverse energy (MET) is used as a proxy of neutrinos system momentum. For each event, mass is calculated over kinematically allowed phase space of the decay angles, and configuration with the highest probability is chosen as a final mass decision. Recent efforts addressed MMC re-tuning to the updated reconstruction of the ATLAS core software Athena. A new, data-set independent, approach for MET resolution estimation based on MET significance has been introduced. A faster scheme for the mass estimation is also suggested. These results as well as plans for further developments are presented.