Measuring the CP state of tau lepton pairs from Higgs decay at the ILC

Abstract

In the Standard Model, the Higgs boson is a CP-even state with CP-conserving couplings; any deviations from this would be a sign of new physics. These CP properties can be probed by measuring Higgs decays to τ lepton pairs, in which the transverse correlation between the τ spins depends on CP. This paper develops such an analysis, using full simulation of signal and background events in the International Large Detector concept for the International Linear Collider. We consider Higgs-strahlung events (e þ e − → HZ) in which the Z boson decays to electrons, muons, or hadrons, and the Higgs boson decays to τ leptons, which then decay either to τ AE → π AE ν or τ AE → π AE π 0 ν. Assuming 2 ab −1 of integrated luminosity at a center-of-mass energy of 250 GeV, the mixing angle between even and odd CP components of the τ pair from Higgs boson decays can be measured to a precision of 75 mrad (4.3°).

Aligned CP-violating Higgs sector canceling the electric dipole moment

“…As discussed in refs. [56][57][58][59], the hadronic decays of τ can be useful to extract the CP-violating effects due to their simple kinematic structure. We thus consider H 0 j → τ − τ + → h − νh +ν , where h ± are hadrons, for instance, ρ ± or π ± mesons.…”

“…[51][52][53][54][55]. The CP violation in extended Higgs sectors can also be tested by measuring the angular distribution of the decays of the SM-like Higgs boson and also those of the extra Higgs bosons [56][57][58][59][60][61][62][63]. However, such additional CP-violating phases are strongly constrained by the EDM data, so that it is generally difficult to keep the sufficient amount of CP-violating phases.…”

Searching for Light Boson via the Yukawa Process at Lepton Colliders

“…Jets are clustered using the longitudinal-kT algorithm with R = 0.4. In Delphes3, we assumed that the tau tagging efficiency of τ jets ( τ ) is 60% [6] or τ = 90% [7]. For both the cases we fix the mis-tagging rate at 0.5%.…”

Probing CP-violating Higgs sectors via the precision measurement of coupling constants

“…(15) is allowed by the EDM data [84]. There is another constraint on Im We here give a comment that the angular distribution of H 1 → τ − τ + can be used to measure the CP violating effect in the Higgs sector [6]. The CP mixing angle ψ CP is given by L H 1 τ τ = gτ (cos ψ CP + iγ 5 sin ψ CP )τ H 1 ,…”