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T: Fachverband Teilchenphysik

T 88: Top quarks: associated production

T 88.1: Vortrag

Donnerstag, 2. April 2020, 16:30–16:45, L-4.001

tt+Z production in the Z→ bb channel at the CMS experiment — Ulrich Husemann, Matthias Schröder, and •Jan van der Linden — Institut für Experimentelle Teilchenphysik (ETP), Karlsruher Institut für Technologie (KIT)

The production of tt+Z is a direct probe of the weak coupling of the Z boson to the top quark. Contributions of BSM interactions, changing the coupling of the Z boson to the top quarks, might be identified by studying this process. The tt+Z process has already been successfully measured in final states with two or more charged leptons. In these multi-lepton analyses also first effective field theory interpretations have been performed.

A measurement of the tt+Z process in an additional phase space region targeting the Z→ bb decay is performed. This can improve the sensitivity to the coupling of the top quark to the Z boson.

The analysis also builds the ground work for a combined measurement of the tt+Z and tt+H processes in the Z→ bb and H→ bb final states for LHC Run-II data. This is especially interesting, as these two processes share similar kinematic features and production probabilities, and are therefore inherently hard to separate from each other. The analysis strategy devised explicitly aims at distinguishing the tt+H and tt+Z contributions in the analyzed region as much as possible.

In this talk an overview of the analysis strategy and methods for an enhanced tt+H and tt+Z separation is given.