Baringer, Philip S.Bean, AliceHensel, CarstenMoulik, TaniaWilson, Graham Wallace2014-10-282014-10-282007-05-01V. M. Abazov et al. (DØ Collaboration). (2007). "Evidence for Production of Single Top Quarks and First Direct Measurement of |V(tb)|." Physical Review Letters, 98(18)181802. http://dx.doi.org/10.1103/PhysRevLett.98.1818020031-9007https://hdl.handle.net/1808/15404This is the publisher's version, also available electronically from http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.98.181802.The D0 Collaboration presents first evidence for the production of single top quarks at the Fermilab Tevatron pp-bar collider. Using a 0.9  fb(−1) dataset, we apply a multivariate analysis to separate signal from background and measure σ(pp-bar→tb+X,tqb+X)=4.9±1.4  pb. The probability to measure a cross section at this value or higher in the absence of a signal is 0.035%, corresponding to a 3.4 standard deviation significance. We use the cross section measurement to directly determine the Cabibbo-Kobayashi-Maskawa matrix element that describes the Wtb coupling and find 0.68<|V(tb)|≤1 at 95% C.L. within the standard model.Article10.1103/PhysRevLett.98.181802openAccess