Karlsruhe 2024 – scientific programme

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T: Fachverband Teilchenphysik

T 50: Top physics 2 (top pair cross section)

T 50.5: Talk

Tuesday, March 5, 2024, 17:00–17:15, Geb. 30.95: Audimax

Measurement of the dileptonic tt differential cross section in a BSM phase space at CMS — Valeria Botta, Lutz Feld, •Danilo Meuser, Philipp Nattland, and Marius Teroerde — I. Physikalisches Insitut B, RWTH Aachen University

Measurements of the tt production cross section yield important precision tests of the Standard Model (SM), while also probing scenarios for physics beyond the SM (BSM). This analysis aims to measure the tt cross section in a phase space where additional contributions from BSM scenarios could be present. It is based on the data set recorded by CMS in the years 2016 to 2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb⁻¹. The BSM scenarios considered include supersymmetric and dark matter models, where, similarly to the dileptonic tt channel, two leptons, b jets and undetected particles are produced.

Unlike previous measurements, where the differential cross sections were mainly measured as a function of kinematic variables of the leptons or top quarks, this analysis focuses on observables related to the neutrinos, like the missing transverse momentum and the angular distance between the missing transverse momentum and the nearest lepton, to separate BSM from SM tt events. In order to increase the sensitivity of the analysis multivariant techniques are used which improve the resolution of the missing transverse momentum in SM tt events. The final results of the differential cross section measurements are compared to monte carlo simulations and fixed order theory predictions.

Keywords: Top pair production; Cross section measurement; BSM physics; Deep neural networks; Unfolding