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Measurement of the production cross-section of a single top quark in association with a W boson at 8 TeV with the ATLAS experiment

  • Author(s): The ATLAS collaboration
  • Aad, G
  • Abbott, B
  • Abdallah, J
  • Abdinov, O
  • Aben, R
  • Abolins, M
  • AbouZeid, OS
  • Abramowicz, H
  • Abreu, H
  • Abreu, R
  • Abulaiti, Y
  • Acharya, BS
  • Adamczyk, L
  • Adams, DL
  • Adelman, J
  • Adomeit, S
  • Adye, T
  • Affolder, AA
  • Agatonovic-Jovin, T
  • Agricola, J
  • Aguilar-Saavedra, JA
  • Ahlen, SP
  • Ahmadov, F
  • Aielli, G
  • Akerstedt, H
  • Åkesson, TPA
  • Akimov, AV
  • Alberghi, GL
  • Albert, J
  • Albrand, S
  • Alconada Verzini, MJ
  • Aleksa, M
  • Aleksandrov, IN
  • Alexa, C
  • Alexander, G
  • Alexopoulos, T
  • Alhroob, M
  • Alimonti, G
  • Alio, L
  • Alison, J
  • Alkire, SP
  • Allbrooke, BMM
  • Allport, PP
  • Aloisio, A
  • Alonso, A
  • Alonso, F
  • Alpigiani, C
  • Altheimer, A
  • Alvarez Gonzalez, B
  • Álvarez Piqueras, D
  • Alviggi, MG
  • Amadio, BT
  • Amako, K
  • Amaral Coutinho, Y
  • Amelung, C
  • Amidei, D
  • Amor Dos Santos, SP
  • Amorim, A
  • Amoroso, S
  • Amram, N
  • Amundsen, G
  • Anastopoulos, C
  • Ancu, LS
  • Andari, N
  • Andeen, T
  • Anders, CF
  • Anders, G
  • Anders, JK
  • Anderson, KJ
  • Andreazza, A
  • Andrei, V
  • Angelidakis, S
  • Angelozzi, I
  • Anger, P
  • Angerami, A
  • Anghinolfi, F
  • Anisenkov, AV
  • Anjos, N
  • Annovi, A
  • Antonelli, M
  • Antonov, A
  • Antos, J
  • Anulli, F
  • Aoki, M
  • Aperio Bella, L
  • Arabidze, G
  • Arai, Y
  • Araque, JP
  • Arce, ATH
  • Arduh, FA
  • Arguin, JF
  • Argyropoulos, S
  • Arik, M
  • Armbruster, AJ
  • Arnaez, O
  • Arnold, H
  • Arratia, M
  • Arslan, O
  • Artamonov, A
  • et al.
Abstract

© 2016, The Author(s). The cross-section for the production of a single top quark in association with a W boson in proton-proton collisions at √s = 8TeV is measured. The dataset corresponds to an integrated luminosity of 20.3 fb−1, collected by the ATLAS detector in 2012 at the Large Hadron Collider at CERN. Events containing two leptons and one central b-jet are selected. The W t signal is separated from the backgrounds using boosted decision trees, each of which combines a number of discriminating variables into one classifier. Production of W t events is observed with a significance of 7.7σ. The cross-section is extracted in a profile likelihood fit to the classifier output distributions. The W t cross-section, inclusive of decay modes, is measured to be 23.0 ± 1.3(stat.)− 3.5+ 3.2(syst.)±1.1(lumi.) pb. The measured cross-section is used to extract a value for the CKM matrix element |Vtb| of 1.01 ± 0.10 and a lower limit of 0.80 at the 95% confidence level. The cross-section for the production of a top quark and a W boson is also measured in a fiducial acceptance requiring two leptons with pT> 25 GeV and |η| < 2.5, one jet with pT> 20 GeV and |η| < 2.5, and ETmiss > 20 GeV, including both W t and top-quark pair events as signal. The measured value of the fiducial cross-section is 0.85 ± 0.01(stat.)− 0.07+ 0.07(syst.)±0.03(lumi.) pb.

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