# Evidence for the Associated Production of a Single Top Quark and a Photon in Proton-Proton Collisions at √s = 13 TeV

CMS Collaboration; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Dragicevic, M.; Erö, J.; Escalante Del Valle, A.; Flechl, M.; Frühwirth, R.; Ghete, V. M.; Hrubec, J.; Jeitler, M.; Krammer, N.; Krätschmer, I.; Liko, D.; Madlener, T.; Mikulec, I.; ... mehr

##### Abstract:
The first evidence of events consistent with the production of a single top quark in association with a photon is reported. The analysis is based on proton-proton collisions at √s=13  TeV and recorded by the CMS experiment in 2016, corresponding to an integrated luminosity of 35.9  fb−1. Events are selected by requiring the presence of a muon (μ), a photon (γ), an imbalance in transverse momentum from an undetected neutrino (ν), and at least two jets (j) of which exactly one is identified as associated with the hadronization of a b quark. A multivariate discriminant based on topological and kinematic event properties is employed to separate signal from background processes. An excess above the background-only hypothesis is observed, with a significance of 4.4 standard deviations. A fiducial cross section is measured for isolated photons with transverse momentum greater than 25 GeV in the central region of the detector. The measured product of the cross section and branching fraction is σ(pp→tγj)B(t→μνb)=115±17(stat)±30(syst)  fb, which is consistent with the standard model prediction.

 Zugehörige Institution(en) am KIT Institut für Experimentelle Teilchenphysik (ETP)Institut für Prozessdatenverarbeitung und Elektronik (IPE) Publikationstyp Zeitschriftenaufsatz Publikationsjahr 2018 Sprache Englisch Identifikator ISSN: 0031-9007, 1079-7114 urn:nbn:de:swb:90-891529 KITopen-ID: 1000089152 Erschienen in Physical review letters Verlag American Physical Society (APS) Band 121 Heft 22 Seiten Article: 221802 Bemerkung zur Veröffentlichung Gefördert durch SCOAP3 Vorab online veröffentlicht am 29.11.2018 Nachgewiesen in Web of ScienceScopus
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