A Method to Estimate the Boson Mass and to Optimise Sensitivity to Helicity Correlations of tau+tau- Final States

TL;DR

This paper introduces a new analysis method for reconstructing the tau+tau- rest frame in proton-proton collisions, enabling improved boson mass estimation and enhanced sensitivity to helicity correlations, especially for hadronic tau decays.

Contribution

A novel technique to reconstruct the tau+tau- rest frame by minimizing acollinearity, improving boson mass estimation and helicity correlation analysis in high-energy collisions.

Findings

Effective tau+tau- rest frame reconstruction method.

Enhanced sensitivity to helicity correlations.

Improved boson mass estimation accuracy.

Abstract

In proton-proton collisions at LHC energies, Z and low mass Higgs bosons would be produced with high and predominantly longitudinal boost with respect to the beam axis. This note describes a new analysis tool devised to handle this situation in cases when such bosons decay to a pair of tau-leptons. The tool reconstructs the rest frame of the tau+tau- pair by finding the boost that minimises the acollinearity between the visible tau decay products. In most cases this gives a reasonable approximation to the rest frame of the decaying boson. It is shown how the reconstructed rest frame allows for a new method of mass estimation. Also a considerable gain in sensitivity to helicity correlations is obtained by analysing the tau-jets in the reconstructed frame instead of using the laboratory momenta and energies, particularly when both tau-leptons decay hadronically.