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Measurement of the energy asymmetry in t(t)over-barj production at 13 TeV with the ATLAS experiment and interpretation in the SMEFT framework

Aad, G; Abbott, B; Abbott, DC; Abud, A Abed; Abeling, K; Abhayasinghe, DK; Abidi, SH; ... Zwalinski, L; + view all (2022) Measurement of the energy asymmetry in t(t)over-barj production at 13 TeV with the ATLAS experiment and interpretation in the SMEFT framework. The European Physical Journal C , 82 (4) , Article 374. 10.1140/epjc/s10052-022-10101-w. Green open access

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Abstract

A measurement of the energy asymmetry in jet-associated top-quark pair production is presented using $$139\,{\mathrm {fb}}^{-1}$$<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>139</mml:mn> <mml:mspace /> <mml:msup> <mml:mrow> <mml:mi>fb</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> of data collected by the ATLAS detector at the Large Hadron Collider during pp collisions at $$\sqrt{s}=13\,\text {TeV}$$<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>13</mml:mn> <mml:mspace /> <mml:mtext>TeV</mml:mtext> </mml:mrow> </mml:math>. The observable measures the different probability of top and antitop quarks to have the higher energy as a function of the jet scattering angle with respect to the beam axis. The energy asymmetry is measured in the semileptonic $$t{\bar{t}}$$<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>t</mml:mi> <mml:mover> <mml:mrow> <mml:mi>t</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> </mml:math> decay channel, and the hadronically decaying top quark must have transverse momentum above $$350\,\text {GeV}$$<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>350</mml:mn> <mml:mspace /> <mml:mtext>GeV</mml:mtext> </mml:mrow> </mml:math>. The results are corrected for detector effects to particle level in three bins of the scattering angle of the associated jet. The measurement agrees with the SM prediction at next-to-leading-order accuracy in quantum chromodynamics in all three bins. In the bin with the largest expected asymmetry, where the jet is emitted perpendicular to the beam, the energy asymmetry is measured to be $$-0.043\pm 0.020$$<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>0.043</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.020</mml:mn> </mml:mrow> </mml:math>, in agreement with the SM prediction of $$-0.037\pm 0.003$$<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>0.037</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.003</mml:mn> </mml:mrow> </mml:math>. Interpreting this result in the framework of the Standard Model effective field theory (SMEFT), it is shown that the energy asymmetry is sensitive to the top-quark chirality in four-quark operators and is therefore a valuable new observable in global SMEFT fits.

Type: Article
Title: Measurement of the energy asymmetry in t(t)over-barj production at 13 TeV with the ATLAS experiment and interpretation in the SMEFT framework
Open access status: An open access version is available from UCL Discovery
DOI: 10.1140/epjc/s10052-022-10101-w
Publisher version: https://doi.org/10.1140/epjc/s10052-022-10101-w
Language: English
Additional information: This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third-party material in this article are included in the Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/
Keywords: Science & Technology, Physical Sciences, Physics, Particles & Fields, Physics, QUARK PAIR PRODUCTION, PARTON DISTRIBUTIONS, PLUS PLUS
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL
URI: https://discovery.ucl.ac.uk/id/eprint/10148381
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