Search for flavour-changing neutral current interactions of the top quark and the Higgs boson in events with a pair of <i>τ</i>-leptons in <i>pp</i> collisions at √s=13 TeV with the ATLAS detector



Aad, G, Abbott, B, Abbott, DC, Abeling, K, Abidi, SH, Aboulhorma, A, Abramowicz, H, Abreu, H, Abulaiti, Y, Abusleme Hoffman, AC
et al (show 2889 more authors) (2023) Search for flavour-changing neutral current interactions of the top quark and the Higgs boson in events with a pair of <i>τ</i>-leptons in <i>pp</i> collisions at √s=13 TeV with the ATLAS detector. JOURNAL OF HIGH ENERGY PHYSICS, 2023 (6). 155-.

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Abstract

<jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>A search for flavour-changing neutral current (FCNC) <jats:italic>tqH</jats:italic> interactions involving a top quark, another up-type quark (<jats:italic>q</jats:italic> = <jats:italic>u, c</jats:italic>), and a Standard Model (SM) Higgs boson decaying into a <jats:italic>τ</jats:italic>-lepton pair (<jats:italic>H</jats:italic> → <jats:italic>τ</jats:italic><jats:sup>+</jats:sup><jats:italic>τ</jats:italic><jats:sup><jats:italic>−</jats:italic></jats:sup>) is presented. The search is based on a dataset of <jats:italic>pp</jats:italic> collisions at <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \sqrt{s} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math></jats:alternatives></jats:inline-formula> = 13 TeV that corresponds to an integrated luminosity of 139 fb<jats:sup><jats:italic>−</jats:italic>1</jats:sup> recorded with the ATLAS detector at the Large Hadron Collider. Two processes are considered: single top quark FCNC production in association with a Higgs boson (<jats:italic>pp</jats:italic> → <jats:italic>tH</jats:italic>), and top quark pair production in which one of top quarks decays into <jats:italic>Wb</jats:italic> and the other decays into <jats:italic>qH</jats:italic> through the FCNC interactions. The search selects events with two hadronically decaying <jats:italic>τ</jats:italic>-lepton candidates (<jats:italic>τ</jats:italic><jats:sub>had</jats:sub>) or at least one <jats:italic>τ</jats:italic><jats:sub>had</jats:sub> with an additional lepton (<jats:italic>e</jats:italic>, <jats:italic>μ</jats:italic>), as well as multiple jets. Event kinematics is used to separate signal from the background through a multivariate discriminant. A slight excess of data is observed with a significance of 2.3<jats:italic>σ</jats:italic> above the expected SM background, and 95% CL upper limits on the <jats:italic>t → qH</jats:italic> branching ratios are derived. The observed (expected) 95% CL upper limits set on the <jats:italic>t → cH</jats:italic> and <jats:italic>t → uH</jats:italic> branching ratios are <jats:inline-formula><jats:alternatives><jats:tex-math>$$ 9.4\times {10}^{-4}\left({4.8}_{-1.4}^{+2.2}\times {10}^{-4}\right) $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mn>9.4</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:msup> <mml:mfenced> <mml:mrow> <mml:msubsup> <mml:mn>4.8</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1.4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>2.2</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:mfenced> </mml:math></jats:alternatives></jats:inline-formula> and <jats:inline-formula><jats:alternatives><jats:tex-math>$$ 6.9\times {10}^{-4}\left({3.5}_{-1.0}^{+1.5}\times {10}^{-4}\right) $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mn>6.9</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:msup> <mml:mfenced> <mml:mrow> <mml:msubsup> <mml:mn>3.5</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1.0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>1.5</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:mfenced> </mml:math></jats:alternatives></jats:inline-formula>, respectively. The corresponding combined observed (expected) upper limits on the dimension-6 operator Wilson coefficients in the effective <jats:italic>tqH</jats:italic> couplings are <jats:italic>C</jats:italic><jats:sub><jats:italic>cϕ</jats:italic></jats:sub><jats:italic>&lt;</jats:italic> 1<jats:italic>.</jats:italic>35 (0<jats:italic>.</jats:italic>97) and <jats:italic>C</jats:italic><jats:sub><jats:italic>uϕ</jats:italic></jats:sub><jats:italic>&lt;</jats:italic> 1<jats:italic>.</jats:italic>16 (0<jats:italic>.</jats:italic>82).</jats:p>

Item Type: Article
Uncontrolled Keywords: Flavour Changing Neutral Currents, Hadron-Hadron Scattering, Higgs Physics, Top Physics
Divisions: Faculty of Science and Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 25 Jul 2023 14:34
Last Modified: 18 Mar 2024 03:57
DOI: 10.1007/JHEP06(2023)155
Open Access URL: https://link.springer.com/article/10.1007/JHEP06(2...
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3171898