Search for single top-quark production via flavour changing neutral currents at 8 TeV with the ATLAS detector

G. Aad (1) , M.K. Ayoub (2) , A. Bassalat (2) , C. Bécot (2) , S. Binet (2) , C. Bourdarios (2) , D. Delgove (2) , J.-B. de Vivie de Regie (2) , L. Duflot (2) , M. Escalier (2) , L. Fayard (2) , D. Fournier (2) , E.L. Gkougkousis (2) , J-F. Grivaz (2) , T. Guillemin (2) , F. Hariri (2) , S. Henrot-Versille (2) , J. Hrivnac (2) , L. Iconomidou-Fayard (2) , M. Kado (2) , A. Lounis (2) , N. Makovec (2) , N. Morange (2) , C. Nellist (2) , P. Petroff (2) , L. Poggioli (2) , P. Puzo (2) , A. Renaud (2) , D. Rousseau (2) , G. Rybkin (2) , A.C. Schaffer (2) , E. Scifo (2) , L. Serin (2) , S. Simion (2) , R. Tanaka (2) , D. Zerwas (2) , Zhongkai Zhang (2) , Y. Zhao (2) , D. Boumediene (3) , Emmanuel Busato (3) , D. Calvet (3) , S. Calvet (3) , J. Donini (3) , E. Dubreuil (3) , G. Gilles (3) , Ph. Gris (3) , H. Liao (3) , R. Madar (3) , D. Pallin (3) , S.M. Romano Saez (3) , C. Santoni (3) , D. Simon (3) , Timothée Theveneaux-Pelzer (3) , F. Vazeille (3) , Z. Barnovska (4) , N. Berger (4) , M. Delmastro (4) , L. Di Ciaccio (4) , S. Elles (4) , C. Goy (4) , T. Hryn’ova (4) , S. Jézéquel (4) , I. Koletsou (4) , R. Lafaye (4) , J. Leveque (4) , N. Massol (4) , G. Sauvage (4) , E. Sauvan (4) , O. Simard (4) , T. Todorov (4) , E. Yatsenko (4) , I. Wingerter-Seez (4) , S. Albrand (5) , J. Brown (5) , J. Collot (5) , S. Crépé-Renaudin (5) , P.A. Delsart (5) , C. Gabaldon (5) , M.H. Genest (5) , J.Y. Hostachy (5) , F. Ledroit-Guillon (5) , A. Lleres (5) , A. Lucotte (5) , F. Malek (5) , C. Monini (5) , J. Stark (5) , B. Trocmé (5) , M. Wu , L. Alio (1) , M. Barbero (1) , Y. Coadou (1) , C. Diaconu (1) , Sara Diglio (1) , F. Djama (1) , O. Duccu (1) , L. Feligioni (1) , J. Gao (1) , G.D. Hallewell (1) , F. Hubaut (1) , S.J. Kahn (1) , E. B. F. G. Knoops (1) , E. Le Guirriec (1) , J. Liu (1) , K. Liu (1) , D. Madaffari (1) , K. Mochizuki (1) , E. Monnier (1) , S. Muanza (1) , Y. Nagai (1) , E. Nagy (1) , P. Pralavorio (1) , A. Rozanov (1) , T. Serre (1) , M. Talby (1) , R.E. Ticse Torres (1) , E. Tiouchichine (1) , S. Tisserant (1) , J. Toth (1) , F. Touchard (1) , L. Vacavant (1)

1 CPPM - Centre de Physique des Particules de Marseille
2 LAL - Laboratoire de l'Accélérateur Linéaire
3 LPC - Laboratoire de Physique Corpusculaire - Clermont-Ferrand
4 LAPP - Laboratoire d'Annecy de Physique des Particules
5 LPSC - Laboratoire de Physique Subatomique et de Cosmologie

A search for single top-quark production via flavour changing neutral current processes from gluon plus up- or charm--quark initial states in proton--proton collisions at the LHC is presented. Data collected with the ATLAS detector in 2012 at a centre-of-mass energy of 8 TeV and corresponding to an integrated luminosity of 20.3 fb−1 are used. Candidate events for a top quark decaying into a lepton, a neutrino and a jet are selected and classified into signal- and background-like candidates using a neural network. No signal is observed and an upper limit on the production cross-section multiplied by the t→Wb branching fraction is set. The observed 95 % CL limit is σqg→t×B(t→Wb)<3.4 pb and the expected 95% CL limit is σqg→t×B(t→Wb)<2.9 pb. The observed limit can be interpreted as upper limits on the coupling constants of the flavour changing neutral current interactions divided by the scale of new physics κugt/Λ<5.8×10−3 TeV−1 and κcgt/Λ<13×10−3 TeV−1 and on the branching fractions B(t→ug)<4×10−5 and B(t→cg)<17×10−5.

Domaines: Physique des Hautes Energies - Expérience [hep-ex]

G. Aad, M.K. Ayoub, A. Bassalat, C. Bécot, S. Binet, et al.. Search for single top-quark production via flavour changing neutral currents at 8 TeV with the ATLAS detector. European Physical Journal C: Particles and Fields, 2016, 76, pp.55. ⟨10.1140/epjc/s10052-016-3876-4⟩. ⟨in2p3-01191610⟩