TY - JOUR
T1 - Search for flavour-changing neutral-current couplings between the top quark and the photon with the ATLAS detector at s=13 TeV
AU - The ATLAS collaboration
AU - Aad, G.
AU - Abbott, B.
AU - Abbott, D. C.
AU - Abdinov, O.
AU - Abud, A. Abed
AU - Abeling, K.
AU - Abhayasinghe, D. K.
AU - Abidi, S. H.
AU - AbouZeid, O. S.
AU - Abraham, N. L.
AU - Abramowicz, H.
AU - Abreu, H.
AU - Abulaiti, Y.
AU - Acharya, B. S.
AU - Achkar, B.
AU - Adachi, S.
AU - Adam, L.
AU - Bourdarios, C. Adam
AU - Adamczyk, L.
AU - Adamek, L.
AU - Adelman, J.
AU - Adersberger, M.
AU - Adiguzel, A.
AU - Adorni, S.
AU - Adye, T.
AU - Affolder, A. A.
AU - Afik, Y.
AU - Agapopoulou, C.
AU - Agaras, M. N.
AU - Aggarwal, A.
AU - Agheorghiesei, C.
AU - Aguilar-Saavedra, J. A.
AU - Barak, L.
AU - Bella, G.
AU - Benhammou, Y.
AU - Biswal, J. P.
AU - Cao, T.
AU - Chen, B.
AU - Cohen, H.
AU - Etzion, E.
AU - Koren, G.
AU - Kuprash, O.
AU - Lutz, M. S.
AU - Oren, Y.
AU - Dominguez, L. Pascual
AU - Pitt, M.
AU - Reikher, D.
AU - Soffer, A.
AU - Tamir, N. M.
AU - Vannicola, D.
N1 - Publisher Copyright:
© 2022 The Author(s)
PY - 2023/7/10
Y1 - 2023/7/10
N2 - This letter documents a search for flavour-changing neutral currents (FCNCs), which are strongly suppressed in the Standard Model, in events with a photon and a top quark with the ATLAS detector. The analysis uses data collected in pp collisions at s=13 TeV during Run 2 of the LHC, corresponding to an integrated luminosity of 139 fb−1. Both FCNC top-quark production and decay are considered. The final state consists of a charged lepton, missing transverse momentum, a b-tagged jet, one high-momentum photon and possibly additional jets. A multiclass deep neural network is used to classify events either as signal in one of the two categories, FCNC production or decay, or as background. No significant excess of events over the background prediction is observed and 95% CL upper limits are placed on the strength of left- and right-handed FCNC interactions. The 95% CL bounds on the branching fractions for the FCNC top-quark decays, estimated (expected) from both top-quark production and decay, are B(t→uγ)<0.85(0.88−0.25 +0.37)×10−5 and B(t→cγ)<4.2(3.40−0.95 +1.35)×10−5 for a left-handed tqγ coupling, and B(t→uγ)<1.2(1.20−0.33 +0.50)×10−5 and B(t→cγ)<4.5(3.70−1.03 +1.47)×10−5 for a right-handed coupling.
AB - This letter documents a search for flavour-changing neutral currents (FCNCs), which are strongly suppressed in the Standard Model, in events with a photon and a top quark with the ATLAS detector. The analysis uses data collected in pp collisions at s=13 TeV during Run 2 of the LHC, corresponding to an integrated luminosity of 139 fb−1. Both FCNC top-quark production and decay are considered. The final state consists of a charged lepton, missing transverse momentum, a b-tagged jet, one high-momentum photon and possibly additional jets. A multiclass deep neural network is used to classify events either as signal in one of the two categories, FCNC production or decay, or as background. No significant excess of events over the background prediction is observed and 95% CL upper limits are placed on the strength of left- and right-handed FCNC interactions. The 95% CL bounds on the branching fractions for the FCNC top-quark decays, estimated (expected) from both top-quark production and decay, are B(t→uγ)<0.85(0.88−0.25 +0.37)×10−5 and B(t→cγ)<4.2(3.40−0.95 +1.35)×10−5 for a left-handed tqγ coupling, and B(t→uγ)<1.2(1.20−0.33 +0.50)×10−5 and B(t→cγ)<4.5(3.70−1.03 +1.47)×10−5 for a right-handed coupling.
UR - http://www.scopus.com/inward/record.url?scp=85146929561&partnerID=8YFLogxK
U2 - 10.1016/j.physletb.2022.137379
DO - 10.1016/j.physletb.2022.137379
M3 - ???researchoutput.researchoutputtypes.contributiontojournal.article???
AN - SCOPUS:85146929561
SN - 0370-2693
VL - 842
JO - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
JF - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
M1 - 137379
ER -