Measurement of the ratio in pp collisions at
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.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP)
- Contributing Organization:
- CMS Collaboration
- Grant/Contract Number:
- AC02-07CH11359
- OSTI ID:
- 1228394
- Alternate ID(s):
- OSTI ID: 1151737
- Report Number(s):
- FERMILAB-PUB-14-087-CMS; CMS-TOP-12-035; CERN-PH-EP-2014-052; S037026931400481X; PII: S037026931400481X
- Journal Information:
- Physics Letters B, Journal Name: Physics Letters B Vol. 736 Journal Issue: C; ISSN 0370-2693
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- Netherlands
- Language:
- English
Web of Science
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