New Paper

New ATLAS group paper

December 9, 2021

Collider Physics Group

This paper presents a measurement of the four-top-quark production cross section in final states with a single lepton or an opposite-sign lepton pair in association with multiple jets using the full Run 2 dataset collected with the ATLAS detector. With four top quarks produced per event, this is a very rare Standard Model process with a predicted cross section of only 12 fb, and thus is very sensitive to beyond-the-SM contributions.

A sophisticated event categorization and multivariate technique is used to discriminate signal from background events. The result of this analysis is combined with a previous measurement in multilepton final states. The combined cross section is measured to be a factor of two higher than the SM prediction, although compatible with it within 2.0 standard deviations. The corresponding observed (expected) signal significance is 4.7 (2.6) standard deviations over the background-only prediction.

Members of the IFAE-ATLAS team (Aurelio Juste, Nicola Orlando, and Anil Sonay) have played a leading role in this publication, from designing the analysis strategy to the final multivariate technique and statistical analysis employed.


Latest Group News

New position

Aurelio Juste appointed Deputy Chair of the Publications Committee

March 1, 2023

Aurelio Juste starts as Deputy Chair of the Publications Committee (PubComm) for one year, and will become the Chair for the following year, starting on 1 March 2024.

IFAE organization

New positions in the IFAE Organization

January 16, 2023

Mario Martinez, ICREA professor at IFAE and head of the Gravitational Waves Group, is the new Director of the Experimental Division and takes on the role of IFAE Deputy Director. Martine Bosman, retiring Director of the Experimental Division, assumes the status of IFAE Emeritus.

New Publication

New ATLAS group paper

January 12, 2023

The paper “Search for a new scalar resonance in flavour-changing neutral-current top-quark decays 𝒕 → 𝒒𝑿 (𝒒 = 𝒖, 𝒄), with 𝑿 → 𝒃𝒃bar, in proton-proton collisions at sqrt(s) = 13 TeV with the ATLAS detector” has been submitted to JHEP.