Speaker
Description
The invariant mass of particle resonances is a key analysis variable for LHC physics. For analyses with di-tau final states, the direct calculation of the invariant mass is impossible because tau decays always include neutrinos, which escape detection in LHC detectors. The Missing Mass Calculator (MMC) is an algorithm used by the ATLAS Experiment to calculate the invariant mass of resonances decaying to two tau particles. The MMC solves the system of kinematic equations involving the tau visible decay products by minimizing a likelihood function, making use of the tau mass constraint and probability distributions from Z → ττ decays. Because the algorithm uses Z decays it is most accurate in the Z mass range. This presentation will show that for high mass BSM resonances the MMC mass increasingly deviates from the true value, warranting further studies and the search for solutions to this discrepancy. We will show studies into machine learning solutions to di-tau mass reconstruction, aimed at providing improved accuracy for high-mass resonances. The specific use case is the search for X → SH → bbττ, sensitive to the Two-real-scalar-singlet extension to the Standard Model (TRSM), in which the Standard Model scalar sector is extended by two scalar singlets, labeled as X and S.
