Dr Elizabeth Gallas

Abstract:

The DØ experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid-argon calorimeters and central muon detector, remaining from Run I, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to DØ. © 2006 Elsevier B.V. All rights reserved.

Abstract:

We present the measurement of R = B (t → W b) / B (t → W q) in p over(p, ̄) collisions at sqrt(s) = 1.96 TeV, using 230 pb-1 of data collected by the DØ experiment at the Fermilab Tevatron Collider. We fit simultaneously R and the number (Nt over(t, ̄)) of selected top quark pairs (t over(t, ̄)), to the number of identified b-quark jets in events with one electron or one muon, three or more jets, and high transverse energy imbalance. To improve sensitivity, kinematical properties of events with no identified b-quark jets are included in the fit. We measure R = 1.03-0.17+0.19 (stat + syst), in good agreement with the standard model. We set lower limits of R > 0.61 and | Vt b | > 0.78 at 95% confidence level. © 2006 Elsevier B.V. All rights reserved.

Abstract:

The cross section for the inclusive production of isolated photons has been measured in p over(p, ̄) collisions at sqrt(s) = 1.96   TeV with the DØ detector at the Fermilab Tevatron Collider. The photons span transverse momenta 23 to 300 GeV and have pseudorapidity | η | < 0.9. The cross section is compared with the results from two next-to-leading order perturbative QCD calculations. The theoretical predictions agree with the measurement within uncertainties. © 2006 Elsevier B.V. All rights reserved.

Abstract:

We have searched for a heavy resonance decaying into a Z+jet final state in pp̄ collisions at a center of mass energy of 1.96TeV at the Fermilab Tevatron collider using the D0 detector. No indication for such a resonance was found in a data sample corresponding to an integrated luminosity of 370pb-1. We set upper limits on the cross section times branching fraction for heavy resonance production at the 95% C.L. as a function of the resonance mass and width. The limits are interpreted within the framework of a specific model of excited quark production. © 2006 The American Physical Society.

Abstract:

A search for gaugino pair production with a trilepton signature in the framework of R-parity violating supersymmetry via the couplings λ121, λ122, or λ133 is presented. The data, corresponding to an integrated luminosity of L ≈ 360  pb-1, were collected from April 2002 to August 2004 with the D∅ detector at the Fermilab Tevatron Collider, at a center-of-mass energy of sqrt(s) = 1.96  TeV. This analysis considers final states with three charged leptons with the flavor combinations eeℓ, μμℓ, and eeτ (ℓ = e or μ). No evidence for supersymmetry is found and limits at the 95% confidence level are set on the gaugino pair production cross section and lower bounds on the masses of the lightest neutralino and chargino are derived in two supersymmetric models. © 2006 Elsevier B.V. All rights reserved.