Accelerator Neutrinos

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.