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Title: Evidence for production of single top quarks

Abstract

We present first evidence for the production of single top quarks in the D0 detector at the Fermilab Tevatron pp collider. The standard model predicts that the electroweak interaction can produce a top quark together with an antibottom quark or light quark, without the antiparticle top-quark partner that is always produced from strong-coupling processes. Top quarks were first observed in pair production in 1995, and since then, single top-quark production has been searched for in ever larger data sets. In this analysis, we select events from a 0.9 fb{sup -1} data set that have an electron or muon and missing transverse energy from the decay of a W boson from the top-quark decay, and two, three, or four jets, with one or two of the jets identified as originating from a b hadron decay. The selected events are mostly backgrounds such as W+jets and tt events, which we separate from the expected signals using three multivariate analysis techniques: boosted decision trees, Bayesian neural networks, and matrix-element calculations. A binned likelihood fit of the signal cross section plus background to the data from the combination of the results from the three analysis methods gives a cross section for single top-quark productionmore » of {sigma}(pp{yields}tb+X,tqb+X)=4.7{+-}1.3 pb. The probability to measure a cross section at this value or higher in the absence of signal is 0.014%, corresponding to a 3.6 standard deviation significance. The measured cross section value is compatible at the 10% level with the standard model prediction for electroweak top-quark production. We use the cross section measurement to directly determine the Cabibbo-Kobayashi-Maskawa quark mixing matrix element that describes the Wtb coupling and find |V{sub tb}f{sub 1}{sup L}|=1.31{sub -0.21}{sup +0.25}, where f{sub 1}{sup L} is a generic vector coupling. This model-independent measurement translates into 0.68<|V{sub tb}|{<=}1 at the 95% C.L. in the standard model.« less

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)
Publication Date:
OSTI Identifier:
21250193
Resource Type:
Journal Article
Journal Name:
Physical Review. D, Particles Fields
Additional Journal Information:
Journal Volume: 78; Journal Issue: 1; Other Information: DOI: 10.1103/PhysRevD.78.012005; (c) 2008 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0556-2821
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ANTIPARTICLES; COUPLING; CROSS SECTIONS; D QUARKS; DECISION TREE ANALYSIS; ELECTRONS; FERMILAB TEVATRON; FORECASTING; HADRONS; MATRIX ELEMENTS; MIXING; MULTIVARIATE ANALYSIS; MUONS; NEURAL NETWORKS; PAIR PRODUCTION; PARTICLE DECAY; PROBABILITY; PROTON-PROTON INTERACTIONS; SIMULATION; STANDARD MODEL; STRONG-COUPLING MODEL; T QUARKS; TRANSVERSE ENERGY; U QUARKS; W MINUS BOSONS; W PLUS BOSONS; WEINBERG-SALAM GAUGE MODEL

Citation Formats

Abazov, V M, Alexeev, G D, Kalinin, A M, Kharzheev, Y M, Malyshev, V L, Tokmenin, V V, Vertogradov, L S, Yatsunenko, Y A, Abbott, B, Gutierrez, P, Hossain, S, Jain, S, Rominsky, M, Severini, H, Skubic, P, Strauss, M, Abolins, M, Benitez, J A, Brock, R, and Dyer, J. Evidence for production of single top quarks. United States: N. p., 2008. Web. doi:10.1103/PHYSREVD.78.012005.
Abazov, V M, Alexeev, G D, Kalinin, A M, Kharzheev, Y M, Malyshev, V L, Tokmenin, V V, Vertogradov, L S, Yatsunenko, Y A, Abbott, B, Gutierrez, P, Hossain, S, Jain, S, Rominsky, M, Severini, H, Skubic, P, Strauss, M, Abolins, M, Benitez, J A, Brock, R, & Dyer, J. Evidence for production of single top quarks. United States. https://doi.org/10.1103/PHYSREVD.78.012005
Abazov, V M, Alexeev, G D, Kalinin, A M, Kharzheev, Y M, Malyshev, V L, Tokmenin, V V, Vertogradov, L S, Yatsunenko, Y A, Abbott, B, Gutierrez, P, Hossain, S, Jain, S, Rominsky, M, Severini, H, Skubic, P, Strauss, M, Abolins, M, Benitez, J A, Brock, R, and Dyer, J. Tue . "Evidence for production of single top quarks". United States. https://doi.org/10.1103/PHYSREVD.78.012005.
@article{osti_21250193,
title = {Evidence for production of single top quarks},
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 Vertogradov, L S and Yatsunenko, Y A and Abbott, B and Gutierrez, P and Hossain, S and Jain, S and Rominsky, M and Severini, H and Skubic, P and Strauss, M and Abolins, M and Benitez, J A and Brock, R and Dyer, J},
abstractNote = {We present first evidence for the production of single top quarks in the D0 detector at the Fermilab Tevatron pp collider. The standard model predicts that the electroweak interaction can produce a top quark together with an antibottom quark or light quark, without the antiparticle top-quark partner that is always produced from strong-coupling processes. Top quarks were first observed in pair production in 1995, and since then, single top-quark production has been searched for in ever larger data sets. In this analysis, we select events from a 0.9 fb{sup -1} data set that have an electron or muon and missing transverse energy from the decay of a W boson from the top-quark decay, and two, three, or four jets, with one or two of the jets identified as originating from a b hadron decay. The selected events are mostly backgrounds such as W+jets and tt events, which we separate from the expected signals using three multivariate analysis techniques: boosted decision trees, Bayesian neural networks, and matrix-element calculations. A binned likelihood fit of the signal cross section plus background to the data from the combination of the results from the three analysis methods gives a cross section for single top-quark production of {sigma}(pp{yields}tb+X,tqb+X)=4.7{+-}1.3 pb. The probability to measure a cross section at this value or higher in the absence of signal is 0.014%, corresponding to a 3.6 standard deviation significance. The measured cross section value is compatible at the 10% level with the standard model prediction for electroweak top-quark production. We use the cross section measurement to directly determine the Cabibbo-Kobayashi-Maskawa quark mixing matrix element that describes the Wtb coupling and find |V{sub tb}f{sub 1}{sup L}|=1.31{sub -0.21}{sup +0.25}, where f{sub 1}{sup L} is a generic vector coupling. This model-independent measurement translates into 0.68<|V{sub tb}|{<=}1 at the 95% C.L. in the standard model.},
doi = {10.1103/PHYSREVD.78.012005},
url = {https://www.osti.gov/biblio/21250193}, journal = {Physical Review. D, Particles Fields},
issn = {0556-2821},
number = 1,
volume = 78,
place = {United States},
year = {2008},
month = {7}
}