Prospects Of Constraining The Higgs Boson'S Cp Nature In The Tau Decay Channel At The Lhc

We investigate how precisely the CP nature of the 125 GeV Higgs boson h, parametrized by a scalar-pseudoscalar Higgs mixing angle phi(tau), can be determined in h -> tau(-)tau(+) decay with subsequent tau-lepton decays to charged prongs at the Large Hadron Collider (LHC). We combine two methods in order to define an observable phi(CP)* which is sensitive to phi(tau): We use the rho-decay plane method for tau(-/+) -> rho(-/+) and the impact parameter method for all other major tau decays. For estimating the precision with which phi(tau) can be measured at the LHC (13 TeV) we take into account the tau(-)tau(+) background from Drell-Yan production and perform a Monte Carlo simulation of measurement uncertainties on the phi(CP)* signal and background distributions. We obtain that the mixing angle phi(tau) can be determined with an uncertainty of Delta phi(tau) similar or equal to 15 degrees (9 degrees) at the LHC with an integrated luminosity of 150 fb(-1) (500 fb(-1)), and with Delta phi(tau) approximate to 4 degrees with 3 ab(-1). Future measurements of phi(tau) yield direct information on whether or not there is an extended Higgs-boson sector with Higgs-sector CP violation. We analyze this in the context of a number of two-Higgs-doublet extensions of the Standard Model, namely the so-called aligned model and conventional two-Higgs-doublet extensions with tree-level neutral flavor conservation.