12–13 Dec 2023
DESY Hamburg and Zoom
Europe/Berlin timezone

Measurement of the inclusive $t\bar{t}H$ Cross-Section in the $4\ell$ Final State

13 Dec 2023, 10:00
20m
Seminarraum 7a (DESY Hamburg)

Seminarraum 7a

DESY Hamburg

Top physics Top Parallel

Speaker

Stephen Eggebrecht (Georg-August-Universität Göttingen, II. Physikalisches Institut)

Description

The Higgs boson production in association with a top quark pair plays a key role for studying the Yukawa coupling between the Higgs boson and the top quark. The coupling can be determined by measuring the cross-section of the $t\bar{t}H$ production in various final states using the $140\,\text{fb}^{-1}$ ATLAS dataset at $\sqrt{s}=13\,\text{TeV}$. Multi-lepton final states are rare but pure since most backgrounds are significantly suppressed.
The non-resonant $t\bar{t}H\to4\ell$ process has low production rate and has contributions from Higgs decay modes like $H\to WW^{*}$, $H\to\tau\tau$, and $H\to Z^{*}Z^{*}$. The dominant background arises from $t\bar{t}Z$, $ZZ$, and misidentified leptons from $t\bar{t}$ production. A multiclass dense neural network (DNN) is trained to separate signal events from these backgrounds and to define analysis regions. Additional fake lepton regions are defined to estimate the normalisation of the most important fake contributions. Partially unblinded fit results for the signal strength are presented for the $4\ell$ channel, but also the combined performance of other multi-lepton final states are shown.

Primary author

Stephen Eggebrecht (Georg-August-Universität Göttingen, II. Physikalisches Institut)

Co-authors

Arnulf Quadt (II. Physikalisches Institut, Georg-August-Universität Göttingen) Baptiste Ravina (II. Physikalisches Institut, Georg-August Universität Göttingen) Elizaveta Shabalina (University of Gottingen) Steffen Korn (II Physikalisches Institut, Georg-August-Universität Göttingen)

Presentation materials