Dr Elizabeth Gallas

Abstract:

DØ has measured the inclusive production cross section of W and Z bosons in a sample of 13 pb-1 of data collected at the Fermilab Tevatron. The cross sections, multiplied by their leptonic branching fractions, for production in pp̄ collisions at √s=1.8 TeV are σWB(W→eν)=2.36±0.02±0.08±0.13 nb, σWB(W →μν)=2.09±0.06±0.22±0.11 nb, σZB(Z→e+e -)=0.218±0.008±0.008±0.012 nb, and σZB(Z →μ+μ -)=0.178±0.022±0.021±0.009 nb, where the first uncertainty is statistical and the second systematic; the third reflects the uncertainty in the integrated luminosity. For the combined electron and muon analyses, we find σWB(W→lν)/σZB(Z→l +l-)=10.90±0.52. Assuming standard model couplings, we use this result to determine the width of the W boson, and obtain Γ(W)=2.044±0.097 GeV. ©1999 The American Physical Society.

Abstract:

We have studied tt̄ production using multijet final states in pp̄ collisions at a center-of-mass energy of 1.8 TeV, with an integrated luminosity of 110.3 pb-1. Each of the top quarks with these final states decays exclusively to a bottom quark and a W boson, with the W bosons decaying into quark-antiquark pairs. The analysis has been optimized using neural networks to achieve the smallest expected fractional uncertainty on the tt̄ production cross section, and yields a cross section of 7.1±2.8 (stat)±1.5 (syst) pb, assuming a top quark mass of 172.1 GeV/c2. Combining this result with previous DØ measurements, where one or both of the W bosons decay leptonically, gives a tt̄ production cross section of 5.9±1.2 (stat)±1.1 (syst) pb. ©1999 The American Physical Society.

Abstract:

The DO detector is used to study pp collisions at the 1800 and 630 GeV center-of-mass energies available at the Fermilab Tevatron. To measure jets, the detector uses a sampling calorimeter composed of uranium and liquid argon as the passive and active media, respectively, Understanding the jet energy calibration is not only crucial for precision tests of QCD, but also for the measurement of particle masses and the determination of physics backgrounds associated with new phenomena. This paper describes the energy calibration of jets observed with the DO detector at the two pp center-of-mass energies in the transverse energy and pseudorapidity range ET>8 GeV and |η|<3.