Measuring CP nature of $$h\tau {{\bar{\tau }}}$$ h τ τ ¯ coupling at $$e^-p$$ e - p collider

Abstract

Abstract The proposed future $$e^- p$$ e - p collider provides sufficient energies to produce the Standard Model Higgs Boson (h) through $$W^\pm $$ W ± and Z-Boson fusion in charged and neutral current modes, respectively and to measure its properties. We take this opportunity to investigate the prospect of measuring the CP properties of h through $$h \rightarrow \tau ^{+} \tau ^{-}$$ h → τ + τ - , where $$\tau ^{-}\,\left( \tau ^{+}\right) $$ τ - τ + decays to a charged pion $$\pi ^-\,\left( \pi ^+\right) $$ π - π + and a neutral pion $$\pi ^0$$ π 0 in association with neutrino (anti-neutrino). An interesting CP sensitive angular observable $$\alpha _{\mathrm{CP}}$$ α CP between the two $$\tau $$ τ -leptons decay plane in the $$\pi ^+\pi ^-$$ π + π - centre of mass frame is proposed and investigated in this work. For fixed electron energy of 150 GeV along with 7 (50) TeV of proton energy, the CP phase can be measured approximately to $$25^\circ $$ 25 ∘ ( $$14^\circ $$ 14 ∘ ) at integrated luminosity of 1 ab $$^{-1}$$ - 1 for −80% polarised electron at 95% confidence level.