Münster 2017 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 74: Higgs-Boson 7 (Paarproduktion, Quantenzahlen)

T 74.7: Vortrag

Mittwoch, 29. März 2017, 18:15–18:30, JUR 5

Analysis of τ-spin correlations in Z→τ⁺τ⁻ decays at ATLAS — •Maike Hansen, Philip Bechtle, Klaus Desch, Christian Grefe, Michael Hübner, and Peter Wagner — Universität Bonn

Many theories of physics beyond the Standard Model, such as supersymmetry, predict a CP-mixing in the Higgs to fermions sector which is not excluded by any previous measurement.

In the H→ττ decay channel, the CP-mixing is encoded in the τ-spin correlations. These can be measured based on the angle between the two τ-decay planes. In the hadronic τ-decay modes, this measurement relies on a high purity τ-decay mode classification and a good reconstruction of the (hadronic) τ-decay products which is available now due to the particle flow based τ reconstruction in ATLAS.

For this analysis, we focus on fully hadronic Z→ ττ decays, the major, irreducible background for a Higgs CP-measurement. Using a kinematic cut, a theoretically well-defined CP-asymmetry can be constructed in Z→ττ which mimics the asymmetry in H→ττ. Therefore, a measurement of the angle between the τ-decay planes in Z→ ττ decays gives us the possibility to understand systematic effects and to calibrate and validate the used methods for the application in H→ττ decays.

In this way, we constrain systematic uncertainties on the angular distributions as well as the used tau particle flow reconstruction. This will help to improve the sensitivity of the Higgs CP measurement.