http://commons.lib.niu.edu:80 The Huskie Commons digital repository system captures, stores, indexes, preserves, and distributes digital research material. 2013-06-18T18:34:51Z http://commons.lib.niu.edu/handle/10843/13523 Title: Combination of the Top Quark Mass Measurements from the Tevatron Collider Authors: Hedin, David Abstract: The top quark is the heaviest known elementary particle, with a mass about 40 times larger than the mass of its isospin partner, the bottom quark. It decays almost 100% of the time to a W boson and a bottom quark. Using top-antitop pairs at the Tevatron proton-antiproton collider, the CDF and D0 Collaborations have measured the top quark’s mass in different final states for integrated luminosities of up to 5.8 fb-1. This paper reports on a combination of these measurements that results in a more precise value of the mass than any individual decay channel can provide. It describes the treatment of the systematic uncertainties and their correlations. The mass value determined is 173.18 ± 0.56(stat) ± 0.75(syst) GeV or 173.18 ± 0.94 GeV, which has a precision of ±0.54%, making this the most precise determination of the top-quark mass. 2012-01-01T00:00:00Z http://commons.lib.niu.edu/handle/10843/13522 Title: Measurement of the Differential Cross Section dσ/dt in Elastic pp- Scattering at √s = 1.96 TeV Authors: Hedin, David Abstract: We present a measurement of the elastic differential cross section dσ( pp-→ pp-)/dt as a function of the four-momentum-transfer squared t. The data sample corresponds to an integrated luminosity of ≈ 31 nb-1 collected with the D0 detector using dedicated Tevatron pp- Collider operating conditions at √s = 1.96 TeV and covers the range 0.26 < │t │ < 1:2 GeV2. For │t│< 0.6 GeV2, dσ/dt is described by an exponential function of the form Ae-b│t│with a slope parameter b = 16.86 ± 0.10(stat) ± 0.20(syst) GeV-2. A change in slope is observed at │t│≈ 0.6 GeV2, followed by a more gradual │t│ dependence with increasing values of │t│. 2012-01-01T00:00:00Z http://commons.lib.niu.edu/handle/10843/13521 Title: Combination of CDF and D0 Measurements of the W boson Helicity in Top Quark Decays Authors: Hedin, David Abstract: We report the combination of recent measurements of the helicity of the W boson from top quark decay by the CDF and D0 collaborations, based on data samples corresponding to integrated luminosities of the 2.7-5.4 fb-1 of pp- collisions collected during Run II of the Fermilab Tevatron collider. Combining measurements that simultaneously determine the fractions of the W bosons with longitudinal (f0) and right-handed (f+) helicities, we find f0= 0.722 ± 0.081[±0.062(stat) ± 0.052(syst)] and f+ = -0.033 ± 0.046[±0.034(stat) ± 0.031(syst)]. Combining measurements where one of the helicity fractions is fixed to the value expected in the standard model, we find f0 = 0.682 ± 0.057[±0.035(stat) ± 0.046(syst)] for fixed f+ and f+ = -0.015 ± 0.035[±0.018(stat) ± 0.030(syst)] for fixed f0. The results are consistent with standard model expectations. 2012-04-01T00:00:00Z http://commons.lib.niu.edu/handle/10843/13520 Title: Measurement of the WZ and ZZ Production Cross Sections Using Leptonic Final States in 8.6 fb-1 of pp- Collisions Authors: Hedin, David Abstract: We study the processes pp- → WZ→ l± vl+ l- and pp-→ZZ →l+ l- vv-, where l = e or μ. Using 8.6 fb-1 of integrated luminosity collected by the D0 experiment at the Femilab Tevatron collider, we measure the WZ production cross section to be 4.50 -0.66 pb which is consistent with, but slightly larger than, the prediction of the standard model. The ZZ cross section is measured to be 1.64± 0.46 pb, in agreement with a prediction of the standard model. Combination with an earlier analysis of the ZZ→ l+ l- l+ l- channel yields a ZZ cross section of 1.44 +0.35 -0.34 pb. 2012-06-01T00:00:00Z