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Title: Evidence for tty Production and Measurement of (σ tt)γ/(σ tt)

Using data corresponding to 6.0 fb -1 of pp collisions at √s = 1.96 TeV collected by the CDF II detector, we present a cross section measurement of top-quark pair production with an additional radiated photon, ttγ. The events are selected by looking for a lepton (ell), a photon (γ), significant transverse momentum imbalance (E T), large total transverse energy, and three or more jets, with at least one identified as containing a b quark (b). The ttγ sample requires the photon to have 10 GeV or more of transverse energy, and to be in the central region. Using an event selection optimized for the ttγ candidate sample we measure the production cross section of tt (σ tt), and the ratio of cross sections of the two samples. Control samples in the dilepton+photon and lepton+photon+E T, channels are constructed to aid in decay product identification and background measurements. We observe 30 ttγ candidate events compared to the standard model expectation of 26.9 ± 3.4 events. We measure the ttγ cross section (σ tt) to be 0.18 ± 0.08 pb, and the ratio of σ ttγ to σ tt to be 0.024 ± 0.009. Assuming no tty production, we observe amore » probability of 0.0015 of the background events alone producing 30 events or more, corresponding to 3.0 standard deviations.« less
Authors:
 [1]
  1. et al.
Publication Date:
Report Number(s):
FERMILAB-PUB-11-283-E-PPD
Journal ID: ISSN 1550-7998; arXiv eprint number arXiv:1106.3970; TRN: US1103719
Grant/Contract Number:
AC02-07CH11359
Type:
Accepted Manuscript
Journal Name:
Physical Review. D, Particles, Fields, Gravitation and Cosmology
Additional Journal Information:
Journal Volume: 84; Journal Issue: 3; Journal ID: ISSN 1550-7998
Publisher:
American Physical Society (APS)
Research Org:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Contributing Orgs:
CDF Collaboration
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; B QUARKS; CROSS SECTIONS; DAUGHTER PRODUCTS; FERMILAB COLLIDER DETECTOR; LEPTONS; PAIR PRODUCTION; PHOTONS; PROBABILITY; PRODUCTION; STANDARD MODEL; TRANSVERSE ENERGY; TRANSVERSE MOMENTUM; Experiment-HEP
OSTI Identifier:
1020306
Alternate Identifier(s):
OSTI ID: 1100679