Abstract
The prospects for the measurement of the pseudoscalar admixture in the hττ coupling to a Standard Model Higgs boson of 120 GeV mass are discussed in a quantitative manner for e+e− collisions of 350 GeV centre-of-mass energy. Specific angular distributions in the h→τ+τ−, τ±→ρ±ν̄τ(ντ) decay chain can be used to probe mixing angles of scalar–pseudoscalar hττ couplings. In the discussion of the feasibility of the method, assumptions on the properties of a future detector for an e+e− linear collider such as TESLA are used. The Standard Model Higgsstrahlung production process is taken as an example. For the expected performance of a typical linear collider set-up, the sensitivity of a measurement of the scalar–pseudoscalar mixing angle turned out to be 6°. It will be straightforward to apply our results to estimate the sensitivity of a measurement, in cases another scenario of the Higgs boson sector (Standard Model or not) is chosen by nature. The experimental error of the method is expected to be limited by the statistics.
Highlights
The transverse spin effects in τ pair production can be helpful to distinguish between the scalar J PC = 0++ and pseudoscalar J PC = 0−+ natures of the spin zero (Higgs) particle, once it is discovered in future accelerator experiments
In Ref. [9] we demonstrated that a measurement of the τ impact parameter in oneprong τ decay is useful for the determination of the Higgs boson parity in the H/A0 → τ +τ −; τ ± → ρ±ντ decay chain
We have found that for an integrated luminosity of 1 ab−1, at 350 GeV center-of-mass energy, a high precision LC detector such as the proposed TESLA, should be able to measure the scalar–pseudoscalar mixing angle for the hτ τ coupling with 6◦ accuracy in the case of a Standard Model Higgs boson of 120 GeV mass
Summary
It is necessary to perform Monte Carlo studies, where the significant details of theoretical effects and detector conditions can be included. To enable such studies we have extended the algorithm of Refs. In the rest frame of the ρ+ρ− system we defined the acoplanarity angle φ∗ as the one between the two planes spanned by the immediate decay products (the π± and π0) of the two ρ’s This angular distribution of the τ decay products, which is sensitive to the Higgs boson parity, once additional selection cuts are applied, is measurable using typical properties of a future detector at an e+e− linear collider.
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