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Title: Search for V+A Current in Top-Quark Decays in pp Collisions at {radical}(s)=1.96 TeV

Abstract

We report an upper limit on the fraction of V+A current, f{sub V+A}, in top-quark decays, using approximately 700 pb{sup -1} of pp collisions at {radical}(s)=1.96 TeV acquired by the upgraded Collider Detector at Fermilab. For the decay t{yields}Wb{yields}l{nu}b (where l=e or {mu}), the invariant mass of the charged lepton and the bottom quark jet is sensitive to the polarization of the W boson. We determine f{sub V+A}=-0.06{+-}0.25 given a top-quark mass of 175 GeV/c{sup 2}. We set an upper limit on f{sub V+A} of 0.29 at the 95% confidence level, an improvement by a factor of 2 on the previous best direct limit.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ;  [1]; ; ; ;  [2]
  1. University of Illinois, Urbana, Illinois 61801 (United States)
  2. Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637 (United States) (and others)
Publication Date:
OSTI Identifier:
20955465
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 98; Journal Issue: 7; Other Information: DOI: 10.1103/PhysRevLett.98.072001; (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; B QUARKS; FERMILAB COLLIDER DETECTOR; GEV RANGE 100-1000; LEPTONS; MASS; PARTICLE DECAY; POLARIZATION; PROTON-PROTON INTERACTIONS; T QUARKS; TEV RANGE 01-10; W MINUS BOSONS; W PLUS BOSONS

Citation Formats

Abulencia, A., Budd, S., Ciobanu, C. I., Errede, D., Errede, S., Gerberich, H., Grundler, U., Junk, T. R., Kraus, J., Marino, C. P., Martin, A., Pitts, K., Rogers, E., Taffard, A., Veramendi, G., Zhang, X., Adelman, J., Brubaker, E., Fedorko, W. T., and Furic, I.. Search for V+A Current in Top-Quark Decays in pp Collisions at {radical}(s)=1.96 TeV. United States: N. p., 2007. Web. doi:10.1103/PHYSREVLETT.98.072001.
Abulencia, A., Budd, S., Ciobanu, C. I., Errede, D., Errede, S., Gerberich, H., Grundler, U., Junk, T. R., Kraus, J., Marino, C. P., Martin, A., Pitts, K., Rogers, E., Taffard, A., Veramendi, G., Zhang, X., Adelman, J., Brubaker, E., Fedorko, W. T., & Furic, I.. Search for V+A Current in Top-Quark Decays in pp Collisions at {radical}(s)=1.96 TeV. United States. doi:10.1103/PHYSREVLETT.98.072001.
Abulencia, A., Budd, S., Ciobanu, C. I., Errede, D., Errede, S., Gerberich, H., Grundler, U., Junk, T. R., Kraus, J., Marino, C. P., Martin, A., Pitts, K., Rogers, E., Taffard, A., Veramendi, G., Zhang, X., Adelman, J., Brubaker, E., Fedorko, W. T., and Furic, I.. Fri . "Search for V+A Current in Top-Quark Decays in pp Collisions at {radical}(s)=1.96 TeV". United States. doi:10.1103/PHYSREVLETT.98.072001.
@article{osti_20955465,
title = {Search for V+A Current in Top-Quark Decays in pp Collisions at {radical}(s)=1.96 TeV},
author = {Abulencia, A. and Budd, S. and Ciobanu, C. I. and Errede, D. and Errede, S. and Gerberich, H. and Grundler, U. and Junk, T. R. and Kraus, J. and Marino, C. P. and Martin, A. and Pitts, K. and Rogers, E. and Taffard, A. and Veramendi, G. and Zhang, X. and Adelman, J. and Brubaker, E. and Fedorko, W. T. and Furic, I.},
abstractNote = {We report an upper limit on the fraction of V+A current, f{sub V+A}, in top-quark decays, using approximately 700 pb{sup -1} of pp collisions at {radical}(s)=1.96 TeV acquired by the upgraded Collider Detector at Fermilab. For the decay t{yields}Wb{yields}l{nu}b (where l=e or {mu}), the invariant mass of the charged lepton and the bottom quark jet is sensitive to the polarization of the W boson. We determine f{sub V+A}=-0.06{+-}0.25 given a top-quark mass of 175 GeV/c{sup 2}. We set an upper limit on f{sub V+A} of 0.29 at the 95% confidence level, an improvement by a factor of 2 on the previous best direct limit.},
doi = {10.1103/PHYSREVLETT.98.072001},
journal = {Physical Review Letters},
number = 7,
volume = 98,
place = {United States},
year = {Fri Feb 16 00:00:00 EST 2007},
month = {Fri Feb 16 00:00:00 EST 2007}
}
  • We report the results of a search for a charged Higgs boson in the decays of top quarks produced in pp collisions at a center-of-mass energy of 1.96 TeV. We use a data sample corresponding to an integrated luminosity of 193 pb{sup -1} collected by the upgraded Collider Detector at Fermilab. No evidence for charged Higgs production is found, allowing 95% C.L. upper limits to be placed on BR(t{yields}H{sup +}b) for different charged Higgs decay scenarios. In addition, we present in the minimal supersymmetric standard model (m{sub H{sup {+-}}},tan{beta}) plane the first exclusion regions with radiative and Yukawa coupling corrections.
  • We report on a search for standard model t-channel and s-channel single-top quark production in pp collisions at a center of mass energy of 1.96 TeV. We use a data sample corresponding to 162 pb{sup -1} recorded by the upgraded collider detector at Fermilab. We find no significant evidence for electroweak top quark production and set upper limits at the 95% confidence level on the production cross section, consistent with the standard model: 10.1 pb for the t-channel, 13.6 pb for the s-channel and 17.8 pb for the combined cross section of t- and s-channel.
  • We search for pair production of supersymmetric top quarks (t-tilde{sub 1}), followed by R-parity violating decay t-tilde{sub 1}{yields}{tau}b with a branching ratio {beta}, using 322 pb{sup -1} of pp collisions at {radical}(s)=1.96 TeV collected by the upgraded Collider Detector at Fermilab. Two candidate events pass our final selection criteria, consistent with the standard model expectation. We set upper limits on the cross section {sigma}(t-tilde{sub 1}t-tilde{sub 1})x{beta}{sup 2} as a function of the top-squark mass m(t-tilde{sub 1}). Assuming {beta}=1, we set a 95% confidence level limit m(t-tilde{sub 1})>153 GeV/c{sup 2}. The limits are also applicable to the case of a third-generationmore » scalar leptoquark (LQ{sub 3}) decaying LQ{sub 3}{yields}{tau}b.« less
  • We report a search for single top quark production with the CDF II detector using 2.1 fb{sup -1} of integrated luminosity of pp collisions at {radical}(s)=1.96 TeV. The data selected consist of events characterized by large energy imbalance in the transverse plane and hadronic jets, and no identified electrons and muons, so the sample is enriched in W{yields}{tau}{nu} decays. In order to suppress backgrounds, additional kinematic and topological requirements are imposed through a neural network, and at least one of the jets must be identified as a b quark jet. We measure an excess of signal-like events in agreement withmore » the standard model prediction, but inconsistent with a model without single top quark production by 2.1 standard deviations ({sigma}), with a median expected sensitivity of 1.4{sigma}. Assuming a top quark mass of 175 GeV/c{sup 2} and ascribing the excess to single top quark production, the cross section is measured to be 4.9{sub -2.2}{sup +2.5}(stat+syst) pb, consistent with measurements performed in independent data sets and with the standard model prediction.« less