Professor Chris Hays

Abstract:

The inclusive cross section for production of isolated photons has been measured in pp macro collisions at square root of s = 630 GeV with the D0 detector at the Fermilab Tevatron Collider. The photons span a transverse energy (E(T)) range from 7-49 GeV and have pseudorapidity absolute value of eta < 2.5. This measurement is combined with the previous D0 result at square root of s = 1800 GeV to form a ratio of the cross sections. Comparison of next-to-leading-order QCD with the measured cross section at 630 GeV and the ratio of cross sections show satisfactory agreement in most of the E(T) range.

Abstract:

We describe QUAERO, a method that (i) enables the automatic optimization of searches for physics beyond the standard model, and (ii) provides a mechanism for making high energy collider data generally available. We apply QUAERO to searches for standard model WW, ZZ, and t t macro production, to searches for these objects produced through a new heavy resonance, and to the first direct search for W'-->WZ. Through this interface, we make three data sets collected by the D0 experiment at square root of [s] = 1.8 TeV publicly available.

Abstract:

We report on a measurement of the ratio of the differential cross sections for W and Z boson production as a function of transverse momentum in proton-antiproton collisions at √s = 1.8 TeV. This measurement uses data recorded by the DØ detector at the Fermilab Tevatron in 1994-1995. It represents the first investigation of a proposal that ratios between W and Z observables can be calculated reliably using perturbative QCD, even when the individual observables are not. Using the ratio of differential cross sections reduces both experimental and theoretical uncertainties, and can therefore provide smaller overall uncertainties in the measured mass and width of the W boson than current methods used at hadron colliders. © 2001 Elsevier Science B.V. All rights reserved.

Abstract:

We present a search for electroweak production of single top quarks in ≈90 pb-1 of data collected with the DØ detector at the Fermilab Tevatron collider. Using arrays of neural networks to separate signals from backgrounds, we set upper limits on the cross sections of 17 pb for the s-channel process pp̄ → tb + X, and 22 pb for the t-channel process pp̄ → tqb + X, both at the 95% confidence level. © 2001 Elsevier Science B.V. All rights reserved.

Abstract:

The data collected by DO detector was used to study the decay of heavy particles into electron-positron pairs during collisions. The dielectron invariant mass spectra for the events with both electrons in central region and with one electron in central region and other in forward region of central calorimeter (CC)/end calorimeter (EC) were also studied. PYTHIA was used to determine the product of cross section and branching ratio for the system. The superimposed histograms represented the estimated spectrum from standard model processes and instrumental effects.