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CDF Collaboration,Aaltonen, T.,Adelman, J.,Alvarez Gonzalez, B.,Amerio, S.,Amidei, D.,Anastassov, A.,Annovi, A.,Antos, J.,Apollinari, G.,Appel, J.,Apresyan, A.,Arisawa, T.,Artikov, A.,Asaadi, J.,Ashma North-Holland Pub. Co 2010 Physics letters: B Vol.692 No.4
<P>We report on a CDF measurement of the total cross section and rapidity distribution, d sigma/dy, for gamma*/Z -> e(+)e(-) events in the Z boson mass region (66 < M-ee < 116 GeV/c(2)) produced in p (p) over bar collisions at root s = 1.96 TeV with 2.1 fb(-1) of integrated luminosity. The measured cross section of 257 +/- 16 pb and d sigma/dy distribution are compared with Next-to-Leading-Order (NLO) and Next-to-Next-to-Leading-Order (NNLO) QCD theory predictions with CTEQ and MRST/MSTW parton distribution functions (PDFs). There is good agreement between the experimental total cross section and d sigma/dy measurements with theoretical calculations with the most recent NNLO PDFs. (C) 2010 Elsevier B.V. All rights reserved.</P>
Measurement of the top quark mass in the lepton+jets channel using the lepton transverse momentum
CDF Collaboration,Aaltonen, T.,Alvarez Gonzalez, B.,Amerio, S.,Amidei, D.,Anastassov, A.,Annovi, A.,Antos, J.,Apollinari, G.,Appel, J.A.,Apresyan, A.,Arisawa, T.,Artikov, A.,Asaadi, J.,Ashmanskas, W. North-Holland Pub. Co 2011 Physics letters: B Vol.698 No.5
This Letter reports a measurement of the top quark mass, M<SUB>top</SUB>, in data from pp@? collisions at s=1.96 TeV corresponding to 2.7 fb<SUP>-1</SUP> of integrated luminosity at the Fermilab Tevatron using the CDF II detector. Events with the lepton+jets topology are selected. An unbinned likelihood is constructed based on the dependence of the lepton transverse momentum, P<SUB>T</SUB>, on M<SUB>top</SUB>. A maximum likelihood fit to the data yields a measured mass M<SUB>top</SUB>=176.9+/-8.0<SUB>stat</SUB>+/-2.7<SUB>syst</SUB> GeV/c<SUP>2</SUP>. In this measurement, the contribution by the jet energy scale uncertainty to the systematic error is negligible. The result provides an important consistency test for other M<SUB>top</SUB> measurements where explicit use of the jet energy is made for deriving the top quark mass.
Measurement of W-boson helicity fractions in top-quark decays using cosθ<sup>*</sup>
CDF Collaboration,Aaltonen, T.,Adelman, J.,Akimoto, T.,Alvarez Gonzalez, B.,Amerio, S.,Amidei, D.,Anastassov, A.,Annovi, A.,Antos, J.,Apollinari, G.,Apresyan, A.,Arisawa, T.,Artikov, A.,Ashmanskas, W. North-Holland Pub. Co 2009 Physics letters. Section B Vol.674 No.3
Fully reconstructed tt@?->W<SUP>+</SUP>bW<SUP>-</SUP>b@?->@?νqq@?<SUP>'</SUP>bb@? events are used to determine the fractions of right-handed (f<SUB>+</SUB>) and longitudinally polarized (f<SUB>0</SUB>) 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 1.9fb<SUP>-1</SUP> of pp@? 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 f<SUB>0</SUB>=0.62+/-0.10(stat)+/-0.05(syst) under the assumption that f<SUB>+</SUB>=0, and f<SUB>+</SUB>=-0.04+/-0.04(stat)+/-0.03(syst) with f<SUB>0</SUB> fixed to the theoretically expected value of 0.70. Model-independent fits are also performed and simultaneously determine f<SUB>0</SUB>=0.66+/-0.16(stat)+/-0.05(syst) and f<SUB>+</SUB>=-0.03+/-0.06(stat)+/-0.03(syst). All these results are consistent with standard model expectations.
An additional study of multi-muon events produced in pp@? collisions at s=1.96 TeV
CDF Collaboration,Aaltonen, T.,Alvarez Gonzalez, B.,Amerio, S.,Amidei, D.,Anastassov, A.,Annovi, A.,Antos, J.,Apollinari, G.,Apresyan, A.,Arisawa, T.,Artikov, A.,Ashmanskas, W.,Auerbach, B.,Azfar, F. North-Holland Pub. Co 2012 Physics letters: B Vol.710 No.2
We present one additional study of multi-muon events produced at the Fermilab Tevatron collider and recorded by the CDF II detector. We use a data set acquired with a dedicated dimuon trigger and corresponding to an integrated luminosity of 3.9 fb<SUP>-1</SUP>. We investigate the distribution of the azimuthal angle between the two trigger muons in events containing at least four additional muon candidates to test the compatibility of these events with originating from known QCD processes. We find that this distribution is markedly different from what is expected from such QCD processes and this observation strongly disfavors the possibility that multi-muon events result from an underestimate of the rate of misidentified muons in ordinary QCD events.