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Title: Measurement of the ratio $$B(t \to Wb)/B(t \to Wq)$$ in pp collisions at $$\sqrt{s}$$ = 8 TeV

The ratio of the top-quark branching fractions R=B(t to Wb)/B(t to Wq), where the denominator includes the sum over all down-type quarks (q = b, s, d), is measured in the t t-bar dilepton final state with proton-proton collision data at sqrt(s)=8 TeV from an integrated luminosity of 19.7 inverse femtobarns, collected with the CMS detector. In order to quantify the purity of the signal sample, the cross section is measured by fitting the observed jet multiplicity, thereby constraining the signal and background contributions. By counting the number of b jets per event, an unconstrained value of R=1.014 +/- 0.003 (stat.) +/- 0.032 (syst.) is measured, in good agreement with the standard model prediction. A lower limit R > 0.955 at the 95% confidence level is obtained after requiring R <;=1, and a lower limit on the Cabibbo-Kobayashi-Maskawa matrix element abs(V[tb]) > 0.975 is set at 95% confidence level. The result is combined with a previous CMS measurement of the t-channel single-top-quark cross section to determine the top-quark total decay width, Gamma[t]=1.36 +/- 0.02 (stat.) +0.14/-0.11 (syst.) GeV.
Authors:
 [1]
  1. et al.
Publication Date:
OSTI Identifier:
1228394
Report Number(s):
FERMILAB-PUB-14-087-CMS; CMS-TOP-12-035; CERN-PH-EP-2014-052
Journal ID: ISSN 0370-2693; TRN: US1601023
Grant/Contract Number:
AC02-07CH11359
Type:
Published Article
Journal Name:
Physics Letters. Section B
Additional Journal Information:
Journal Volume: 736; Journal ID: ISSN 0370-2693
Publisher:
Elsevier
Research Org:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Contributing Orgs:
CMS Collaboration
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; hep-ex; High Energy Physics; HEP