PT Journal
AU ATLAS Collaboration (Aad, Gea
   Amos, KR
   Aparisi Pozo, JA
   Bailey, AJ
   Cabrera Urban, S
   Cantero, J
   Cardillo, F
   Castillo Gimenez, V
   Costa, MJ
   Didenko
   Escobar, C
   Fiorini, L
   Fullana Torregrosa, E
   Fuster, J
   Garcia, C
   Garcia Navarro, JE
   Gomez Delegido, AJ
   Gonzalez de la Hoz, S
   Gonzalvo Rodriguez, GR
   Guerrero Rojas, JGR
   Higon-Rodriguez, E
   Lacasta, C
   Lozano Bahilo, JJ
   Marti-Garcia, S
   Martinez Agullo, P
   Miralles Lopez, M
   Mitsou, VA
   Monsonis Romero, L
   Moreno Llacer, M
   Munoz Perez, D
   Navarro-Gonzalez, J
   Poveda, J
   Prades Ibañez, A
   Rubio Jimenez, A
   Ruiz-Martinez, A
   Sabatini, P
   Salt, J
   Sanchez Sebastian, V
   Sayago Galvan, I
   Senthilkumar, V
   Soldevila, U
   Sanchez, J
   Torro Pastor, E
   Valero, A
   Valls Ferrer, JA
   Varriale, L
   Villaplana Perez, M
   Vos, M
TI Search for flavour-changing neutral-current couplings between the top quark and the photon with the ATLAS detector at root s=13 TeV
SO Physics Letters B
JI Phys. Lett. B
PY 2023
BP 137379
EP 22pp
VL 842
DI 10.1016/j.physletb.2022.137379
LA English
AB This letter documents a search for flavour-changing neutral currents (FCNCs), which are strongly sup-pressed 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 & RADIC;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 ex-cess 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 & RARR; u & gamma; ) < 0.85 (0.88+0.37 -0.25) x 10-5 and B(t & RARR; c & gamma; ) < 4.2 (3.40+1.35-0.95) x 10-5 for a left-handed tq & gamma; cou-pling, and B(t & RARR; u & gamma; ) < 1.2 (1.20+0.50 -0.33) x10-5 and B(t & RARR; c & gamma; ) < 4.5 (3.70+1.47 -1.03) x10-5 for a right-handed coupling.
ER