Observation of four-top-quark production in the multilepton final state with the ATLAS detector

Medientyp: E-Artikel
Titel: Observation of four-top-quark production in the multilepton final state with the ATLAS detector
Beteiligte: Aad, G.; Abbott, B.; Abeling, K.; Abicht, N. J.; Abidi, S. H.; Aboulhorma, A.; Abramowicz, H.; Abreu, H.; Abulaiti, Y.; Hoffman, A. C. Abusleme; Acharya, B. S.; Bourdarios, C. Adam; Adamczyk, L.; Adamek, L.; Addepalli, S. V.; Addison, M. J.; Adelman, J.; Adiguzel, A.; Adye, T.; Affolder, A. A.; Afik, Y.; Agaras, M. N.; Agarwala, J.; Aggarwal, A.; [...]
Erschienen: Springer Science and Business Media LLC, 2023
Erschienen in: The European Physical Journal C
Sprache: Englisch
DOI: 10.1140/epjc/s10052-023-11573-0
ISSN: 1434-6052
Schlagwörter: Physics and Astronomy (miscellaneous) ; Engineering (miscellaneous)
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Beschreibung: <jats:title>Abstract</jats:title><jats:p>This paper presents the observation of four-top-quark (<jats:inline-formula><jats:alternatives><jats:tex-math>$$t\bar{t}t\bar{t}$$</jats:tex-math><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: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></jats:alternatives></jats:inline-formula>) production in proton-proton collisions at the LHC. The analysis is performed using an integrated luminosity of 140 <jats:inline-formula><jats:alternatives><jats:tex-math>$$\hbox {fb}^{-1}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mtext>fb</mml:mtext><mml:mrow><mml:mo>-</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:math></jats:alternatives></jats:inline-formula>at a centre-of-mass energy of 13 TeV collected using the ATLAS detector. Events containing two leptons with the same electric charge or at least three leptons (electrons or muons) are selected. Event kinematics are used to separate signal from background through a multivariate discriminant, and dedicated control regions are used to constrain the dominant backgrounds. The observed (expected) significance of the measured<jats:inline-formula><jats:alternatives><jats:tex-math>$$t\bar{t}t\bar{t}$$</jats:tex-math><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: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></jats:alternatives></jats:inline-formula>signal with respect to the standard model (SM) background-only hypothesis is 6.1 (4.3) standard deviations. The<jats:inline-formula><jats:alternatives><jats:tex-math>$$t\bar{t}t\bar{t}$$</jats:tex-math><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: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></jats:alternatives></jats:inline-formula>production cross section is measured to be<jats:inline-formula><jats:alternatives><jats:tex-math>$$22.5^{+6.6}_{-5.5}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>22</mml:mn><mml:mo>.</mml:mo><mml:msubsup><mml:mn>5</mml:mn><mml:mrow><mml:mo>-</mml:mo><mml:mn>5.5</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>6.6</mml:mn></mml:mrow></mml:msubsup></mml:mrow></mml:math></jats:alternatives></jats:inline-formula> fb, consistent with the SM prediction of<jats:inline-formula><jats:alternatives><jats:tex-math>$$12.0 \pm 2.4$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>12.0</mml:mn><mml:mo>±</mml:mo><mml:mn>2.4</mml:mn></mml:mrow></mml:math></jats:alternatives></jats:inline-formula>fb within 1.8 standard deviations. Data are also used to set limits on the three-top-quark production cross section, being an irreducible background not measured previously, and to constrain the top-Higgs Yukawa coupling and effective field theory operator coefficients that affect<jats:inline-formula><jats:alternatives><jats:tex-math>$$t\bar{t}t\bar{t}$$</jats:tex-math><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: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></jats:alternatives></jats:inline-formula>production.</jats:p>
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