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Title: Evidence for Production of Single Top Quarks and First Direct Measurement of vertical bar V{sub tb} vertical bar

Abstract

The D0 Collaboration presents first evidence for the production of single top quarks at the Fermilab Tevatron pp collider. Using a 0.9 fb{sup -1} dataset, we apply a multivariate analysis to separate signal from background and measure {sigma}(pp{yields}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< vertical bar V{sub tb} vertical bar {<=}1 at 95% C.L. within the standard model.

Authors:
; ; ; ; ; ; ; ;  [1]; ; ; ; ; ; ; ; ;  [2]; ;  [3]
  1. Joint Institute for Nuclear Research, Dubna (Russian Federation)
  2. University of Oklahoma, Norman, Oklahoma 73019 (United States)
  3. Michigan State University, East Lansing, Michigan 48824 (United States) (and others)
Publication Date:
OSTI Identifier:
20951329
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 98; Journal Issue: 18; Other Information: DOI: 10.1103/PhysRevLett.98.181802; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; CROSS SECTIONS; FERMILAB TEVATRON; KOBAYASHI-MASKAWA MATRIX; MULTIVARIATE ANALYSIS; PROBABILITY; SIGNALS; STANDARD MODEL; T QUARKS

Citation Formats

Abazov, V. M., Alexeev, G. D., Kalinin, A. M., Kharzheev, Y. M., Malyshev, V. L., Tokmenin, V. V., Eijk, B. van, Vertogradov, L. S., Yatsunenko, Y. A., Abbott, B., Gutierrez, P., Hall, I., Jain, S., Kopal, M., Pompos, A., Severini, H., Skubic, P., Strauss, M., Abolins, M., and Benitez, J. A. Evidence for Production of Single Top Quarks and First Direct Measurement of vertical bar V{sub tb} vertical bar. United States: N. p., 2007. Web. doi:10.1103/PHYSREVLETT.98.181802.
Abazov, V. M., Alexeev, G. D., Kalinin, A. M., Kharzheev, Y. M., Malyshev, V. L., Tokmenin, V. V., Eijk, B. van, Vertogradov, L. S., Yatsunenko, Y. A., Abbott, B., Gutierrez, P., Hall, I., Jain, S., Kopal, M., Pompos, A., Severini, H., Skubic, P., Strauss, M., Abolins, M., & Benitez, J. A. Evidence for Production of Single Top Quarks and First Direct Measurement of vertical bar V{sub tb} vertical bar. United States. doi:10.1103/PHYSREVLETT.98.181802.
Abazov, V. M., Alexeev, G. D., Kalinin, A. M., Kharzheev, Y. M., Malyshev, V. L., Tokmenin, V. V., Eijk, B. van, Vertogradov, L. S., Yatsunenko, Y. A., Abbott, B., Gutierrez, P., Hall, I., Jain, S., Kopal, M., Pompos, A., Severini, H., Skubic, P., Strauss, M., Abolins, M., and Benitez, J. A. Fri . "Evidence for Production of Single Top Quarks and First Direct Measurement of vertical bar V{sub tb} vertical bar". United States. doi:10.1103/PHYSREVLETT.98.181802.
@article{osti_20951329,
title = {Evidence for Production of Single Top Quarks and First Direct Measurement of vertical bar V{sub tb} vertical bar},
author = {Abazov, V. M. and Alexeev, G. D. and Kalinin, A. M. and Kharzheev, Y. M. and Malyshev, V. L. and Tokmenin, V. V. and Eijk, B. van and Vertogradov, L. S. and Yatsunenko, Y. A. and Abbott, B. and Gutierrez, P. and Hall, I. and Jain, S. and Kopal, M. and Pompos, A. and Severini, H. and Skubic, P. and Strauss, M. and Abolins, M. and Benitez, J. A.},
abstractNote = {The D0 Collaboration presents first evidence for the production of single top quarks at the Fermilab Tevatron pp collider. Using a 0.9 fb{sup -1} dataset, we apply a multivariate analysis to separate signal from background and measure {sigma}(pp{yields}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< vertical bar V{sub tb} vertical bar {<=}1 at 95% C.L. within the standard model.},
doi = {10.1103/PHYSREVLETT.98.181802},
journal = {Physical Review Letters},
number = 18,
volume = 98,
place = {United States},
year = {Fri May 04 00:00:00 EDT 2007},
month = {Fri May 04 00:00:00 EDT 2007}
}
  • The D0 Collaboration presents first evidence for the production of single top quarks at the Fermilab Tevatron p{bar p} collider. Using a 0.9 fb{sup -1} dataset, we apply a multivariate analysis to separate signal from background and measure {sigma}(p{bar p} {yields} 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 signal is 0.035%, corresponding to a 3.4 standard deviation significance. We use the cross section measurement to directly determine the CKM matrix element that describes the W tb coupling and find 0.68more » < |V{sub tb}| {le} 1 at 95% C.L.« less
  • An updated measurement of the single top quark production cross section is presented using the full data set collected by the Collider Detector at Fermilab (CDF), corresponding to 9.5 fb -1 of integrated luminosity from proton-antiproton collisions at 1.96 TeV center-of-mass energy. The events selected contain an imbalance in the total transverse momentum, jets identified as containing b quarks, and no identified leptons. The sum of the s- and t-channel single top quark cross sections is measured to be 3.53 -1.16 +1.25 pb and a lower limit on the magnitude of the top-to-bottom quark coupling, |V tb| of 0.63, is obtainedmore » at the 95% credibility level. These measurements are combined with previously reported CDF results obtained from events with an imbalance in total transverse momentum, jets identified as originating from b quarks, and one identified lepton. Furthermore, the combined cross section is measured to be 3.02 -0.48 +0.49 pb and a lower limit on |V tb| of 0.84 is obtained at the 95% credibility level.« less
    Cited by 2
  • An updated measurement of the single top quark production cross section is presented using the full data set collected by the Collider Detector at Fermilab (CDF), corresponding to 9.5 fb -1 of integrated luminosity from proton-antiproton collisions at 1.96 TeV center-of-mass energy. The events selected contain an imbalance in the total transverse momentum, jets identified as containing b quarks, and no identified leptons. The sum of the s- and t-channel single top quark cross sections is measured to be 3.53 -1.16 +1.25 pb and a lower limit on the magnitude of the top-to-bottom quark coupling, |V tb| of 0.63, is obtainedmore » at the 95% credibility level. These measurements are combined with previously reported CDF results obtained from events with an imbalance in total transverse momentum, jets identified as originating from b quarks, and one identified lepton. Furthermore, the combined cross section is measured to be 3.02 -0.48 +0.49 pb and a lower limit on |V tb| of 0.84 is obtained at the 95% credibility level.« less
  • CP-nonconserving effects in the reaction pp-bar-->tb-bar+X--> W{sup +}bb-bar+X, driven by the supersymmetric CP-odd phase of the top squark trilinear soft breaking term arg(A{sub t}), are studied. We discuss the CP-nonconserving effects in both production and the associated decay amplitudes of the top quark. We find that, within a plausible low energy scenario of the MSSM and keeping the neutron electric dipole moment below its current limit, a CP-violating cross-section asymmetry as large as 2-3% can arise if some of the parameters lie in a favorable range. A partial rate asymmetry originating only in the top quark decay t --> W{supmore » +}b is found to be, in general, below the 0.1% level which is somewhat smaller than previous claims. For a low tan beta of order one the decay asymmetry can reach at the most {approx} 0.3%. This (few) percent level overall CP-violating signal in pp-bar --> tb-bar + X --> W{sup +}bb-bar + X might be within the reach of the future 2(4) TeV pp-bar Fermilab Tevatron collider that may be able to produce {approx} 10000 ({approx} 30000) such tb-bar events with an integrated luminosity of 30 fb{sup -1}. In particular, it may be used to place an upper bound on arg(A{sub t}) if indeed arg({mu}) --> 0, as implied from the present experimental limit on the neutron electric dipole moment. The partial rate asymmetry in the top quark decay ({approx} few x 10{sup -3}) may also be within the reach of the CERN LHC with {approx} 10{sup 7} pairs of tt-bar produced, provided detector systematics are sufficiently small. We also show that if the GUT scale universality of the soft breaking trilinear A terms is relaxed, then the phases associated with arg(A{sub u}) and arg(A{sub d}) can take values up to {approx} few x 10{sup -1} even with squarks and gluino masses of several hundred GeV's without contradicting the experimental limit on the neutron electric dipole moment.« less
  • We present measurements of production cross sections of single top quarks in pp collisions at √s = 1.96 TeV in a data sample corresponding to an integrated luminosity of 5.4 fb -1 collected by the D0 detector at the Fermilab Tevatron Collider. We select events with an isolated electron or muon, an imbalance in transverse energy, and two, three, or four jets, with one or two of them containing a bottom hadron. We obtain an inclusive cross section of Σ(pp → tb + X, tqb + X) = 3.43 -0.74 +0.73 pb and use it to extract the CKM matrixmore » element 0.79 < |V tb| {le} 1 at the 95% C.L. We also measure Σ(pp → tb + X) = 0.68 -0.35 +0.38pb and Σ(pp → tqb + X) = 2.86 -0.63 +0.69pb when assuming, respectively, tqb and tb production rates as predicted by the standard model.« less