<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>C</mml:mi><mml:mi>P</mml:mi></mml:math> Properties of Higgs Boson Interactions with Top Quarks in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>t</mml:mi><mml:mover accent="true"><mml:mi>t</mml:mi><mml:mo stretchy="false">¯</mml:mo></mml:mover><mml:mi>H</mml:mi></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>t</mml:mi><mml:mi>H</mml:mi></mml:math> Processes Using <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>H</mml:mi><mml:mo stretchy="false">→</mml:mo><mml:mi>γ</mml:mi><mml:mi>γ</mml:mi></mml:math> with the ATLAS Detector
G. Aad, B. Abbott, D. C. Abbott, A. Abed Abud, K. Abeling, D. K. Abhayasinghe, S. H. Abidi, O. S. AbouZeid, N. L. Abraham, H. Abramowicz, H. Abreu, Y. Abulaiti, B. S. Acharya, B. Achkar, L. Adámek, C. Adam Bourdarios, L. Adamczyk, L. Adámek, J. Adelman, M. Adersberger, A. Adıgüzel, S. Adorni, T. Adye, A. A. Affolder, Y. Afik, C. Agapopoulou, M. N. Agaras, A. Aggarwal, C. Agheorghiesei, J. A. Aguilar–Saavedra, A. Ahmad, F. Ahmadov, W. S. Ahmed, X. Ai, G. Aielli, S. Akatsuka, M. Akbiyik, T. P. A. Åkesson, E. Akilli, A. V. Akimov, K. Al Khoury, G. L. Alberghi, J. Albert, M. J. Alconada Verzini, S. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, T. Alexopoulos, A. Alfonsi, F. Alfonsi, M. Alhroob, B. Ali, S. Ali, M. Aliev, G. Alimonti, C. Allaire, B. M. M. Allbrooke, B. W. Allen, P. P. Allport, A. Aloisio, F. Alonso, C. Alpigiani, E. Alunno Camelia, M. Alvarez Estevez, M. G. Alviggi, Y. Amaral Coutinho, A. Ambler, L Ambroz, Christoph Amelung, D. Amidei, S. P. Amor Dos Santos, S. Amoroso, C. S. Amrouche, F. F. An, C. Anastopoulos, N. Andari, T. Andeen, J. K. Anders, S. Y. Andrean, A. Andreazza, V. Andrei, C. R. Anelli, S. Angelidakis, A. Angerami, A. V. Anisenkov, A. Annovi, C. Antel, M. T. Anthony, E. Antipov, M. Antonelli, D. J. A. Antrim, F. Anulli, M. Aoki, J. A. Aparisi Pozo, M. A. Aparo, L. Aperio Bella, N. Aranzabal, V. Araujo Ferraz, R. Araujo Pereira
Abstract
A study of the charge conjugation and parity ($CP$) properties of the interaction between the Higgs boson and top quarks is presented. Higgs bosons are identified via the diphoton decay channel ($H\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$), and their production in association with a top quark pair ($t\overline{t}H$) or single top quark ($tH$) is studied. The analysis uses $139\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of proton--proton collision data recorded at a center-of-mass energy of $\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}$ with the ATLAS detector at the Large Hadron Collider. Assuming a $CP$-even coupling, the $t\overline{t}H$ process is observed with a significance of 5.2 standard deviations. The measured cross section times $H\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$ branching ratio is ${1.64}_{\ensuremath{-}0.36}^{+0.38}(\text{stat}{)}_{\ensuremath{-}0.14}^{+0.17}(\text{sys})\text{ }\text{ }\mathrm{fb}$, and the measured rate for $t\overline{t}H$ is ${1.43}_{\ensuremath{-}0.31}^{+0.33}(\text{stat}{)}_{\ensuremath{-}0.15}^{+0.21}(\text{sys})$ times the Standard Model expectation. The $tH$ production process is not observed and an upper limit on its rate of 12 times the Standard Model expectation is set. A $CP$-mixing angle greater (less) than 43 $(\ensuremath{-}43)\ifmmode^\circ\else\textdegree\fi{}$ is excluded at 95% confidence level.