Comments and Reply on: "Study of multi-muon events produced in pp̄ interactions at √s = 1.96 TeV"; T. Aaltonen et al. (The CDF collaboration)

The European Physical Journal C-Particles and Fields-publishes scientific manuscripts of relevance to the scientific community following careful and strict peer reviewing and, whenever appropriate and necessary, through discussion with the authors, so as to optimise scientific content and style of presentation prior to publication. In some cases significant disagreement between authors and referees (and/or editors) of the journal cannot be resolved despite all efforts and best of intentions. While the journal-notwithstanding any appeals-retains the right to reject such manuscripts, the editors of this journal may decide, in cases deemed of exceptional interest and potential significance for the field, to accept the manuscript for publication, to amend it by "comments" of the editor(s) in charge and, if appropriate, by a "reply" of the authors of the commented manuscript. The present comment is on "Study of multi-muon events produced in pp̄ interactions at √ = 1.96 TeV"; T. Aaltonen et al. (The CDF Collaboration, Eur. Phys. J. C, 2010, doi:10.1140/epjc/s10052-010-1336-0. © 2010 The Author(s)

Measurement of the single-top-quark production cross section at CDF

We report a measurement of the single-top-quark production cross section in 2.2fb-1 of pp̄ collision data collected by the Collider Detector at Fermilab at s=1.96TeV. Candidate events are classified as signal-like by three parallel analyses which use likelihood, matrix element, and neural network discriminants. These results are combined in order to improve the sensitivity. We observe a signal consistent with the standard model prediction, but inconsistent with the background-only model by 3.7 standard deviations with a median expected sensitivity of 4.9 standard deviations. We measure a cross section of 2.2-0.6+0.7(stat+syst)pb, extract the Cabibbo-Kobayashi-Maskawa matrix-element value |Vtb|=0.88-0.12+0.13(stat+syst)±0.07(theory), and set the limit |Vtb|>0.66 at the 95% C.L. © 2008 The American Physical Society

Search for new color-octet vector particle decaying to tT{topbar} in pP{topbar} collisions at √s=1.96 TeV

We present the result of a search for a massive color-octet vector particle, (e.g. a massive gluon) decaying to a pair of top quarks in proton-antiproton collisions with a center-of-mass energy of 1.96 TeV. This search is based on 1.9 fb-1 of data collected using the CDF detector during Run II of the Tevatron at Fermilab. We study tTtopbar events in the lepton. +. jets channel with at least one b-tagged jet. A massive gluon is characterized by its mass, decay width, and the strength of its coupling to quarks. These parameters are determined according to the observed invariant mass distribution of top quark pairs. We set limits on the massive gluon coupling strength for masses between 400 and 800 GeV/c2 and width-to-mass ratios between 0.05 and 0.50. The coupling strength of the hypothetical massive gluon to quarks is consistent with zero within the explored parameter space. © 2010 Elsevier B.V

Measurement of W-boson helicity fractions in top-quark decays using cos θ*

Fully reconstructed t over(t, ̄) → W+ b W- over(b, ̄) → ℓ ν q over(q, ̄)′ b over(b, ̄) events are used to determine the fractions of right-handed (f+) and longitudinally polarized (f0) W bosons produced in top-quark decays. The helicity fractions are sensitive to the couplings and the Dirac structure of the Wtb vertex. This Letter reports measurements of the W-boson helicity fractions from two different methods using data corresponding to an integrated luminosity of 1.9 fb- 1 of p over(p, ̄) collisions at a center-of-mass energy of 1.96 TeV collected by the CDF II detector operating at the Fermilab Tevatron. Combining the results from the two methods, we find f0 = 0.62 ± 0.10 (stat) ± 0.05 (syst) under the assumption that f+ = 0, and f+ = - 0.04 ± 0.04 (stat) ± 0.03 (syst) with f0 fixed to the theoretically expected value of 0.70. Model-independent fits are also performed and simultaneously determine f0 = 0.66 ± 0.16 (stat) ± 0.05 (syst) and f+ = - 0.03 ± 0.06 (stat) ± 0.03 (syst). All these results are consistent with standard model expectations. © 2009 Elsevier B.V