TauSpinner: a tool for simulating CP effects in H to tau tau decays at LHC

TL;DR

TauSpinner is a versatile tool that enables simulation and analysis of CP properties in Higgs to tau tau decays at the LHC by manipulating spin correlations in existing event samples.

Contribution

The paper introduces TauSpinner as a novel tool for adding or removing spin correlations in tau decay events to measure the Higgs boson's CP state.

Findings

Effective in distinguishing scalar and pseudoscalar CP states.

Applicable to main background processes like Z/gamma* to tau tau.

Provides a practical method for CP analysis in LHC experiments.

Abstract

In this paper, we discuss application of the TauSpinner package as a simulation tool for measuring the CP state of the newly discovered Higgs boson using the transverse spin correlations in the H to tau tau decay channel. We discuss application for its main background Z/gamma* to tau tau as well. The TauSpinner package allows one to add, with the help of weights, transverse spin correlations corresponding to any mixture of scalar/pseudoscalar state, on already existing events using information from the kinematics of outgoing tau leptons and their decay products only. This procedure can be used when polarimetric vectors of the taus decays and density matrix for tau-pair production are not stored with the event sample. We concentrate on the well-defined effects for the Higgs (or Higgs-like scalar) decays, which are physically separated from the production processes. TauSpinner also allows to reintroduce (or remove) spin correlations to events from Drell-Yan Z/gamma* to tau tau process, the main background for the Higgs parity observables, again with the help of weights only. From the literature, we recall well-established observables, developed for measuring the CP of the Higgs, and use them as benchmarks for illustrating applications of the TauSpinner package. We also include a description of the code and prepared testing examples.