Dr Elizabeth Gallas

Abstract:

The inclusive muon cross section, and the cross section for mouns originating from b quark decay, in the forward rapidity region of 2.4 < | ymu | < 3.2 were measured in this study. It was found that next-to-leading order QCD calculations underestimate b quark production by a factor of 4 in this region.

Abstract:

We report on measurements on inclusive cross sections times branching fractions into electrons for W and Z bosons produced in pp̄ collisions at s=1.8 TeV. From an integrated luminosity of 84.5 pb-1 recorded in 1994-1995 using the DØ detector at the Fermilab Tevatron, we determine σ(pp̄→W+X)×B(W→eν) = 2310±10(stat)±50(syst)±100(lum)pb and σ(pp̄→Z+X)×B(Z→ee)=221±3(stat)±4(syst) ±10(lum) pb. From these, we derive σ(pp̄→W+X)×B(W→eν)/σ(pp̄→Z+X) ×B(Z→ee)=10.43±0.15(stat) ±0.20(syst)±0.10(NLO), B(W→eν)=0.1044±0.0015(stat)±0.0020(syst)±0. 0017(theory)±0.0010(NLO), and Γ W=2.169±0.031(stat)±0.042(syst)±0.041(theory) ±0.022(NLO)GeV. We use the latter to set a 95% confidence level upper limit on the partial decay width of the W boson into nonstandard model final states, ΓWinv, of 0.213 GeV. Combining these results with those from the 1992-1993 data gives σ(pp̄→W+X) ×B(W→eν)/σ(pp̄→Z+X)×B(Z→ee)=10. 51±0.25,ΓW=2.152±0.066 GeV, and a 95% C.L. upper limit on ΓWinv of 0.191 GeV. Using a sample with a luminosity of 505 nb-1 taken at s=630 GeV, we measure σ(pp̄→W+X)×B(W→eν)=658±67 pb. ©2000 The American Physical Society.

Abstract:

We present a measurement of the transverse momentum distribution of Z bosons produced in pp collisions at √s = 1.8 TeV from data collected by the D experiment at the Fermilab Tevatron Collider. We find good agreement between our results and current resummation calculations, and also use our data to extract nonperturbative parameters for a particular version of the resummation formalism. The resulting values are significantly more precise than obtained in previous determinations. © 2000 The American Physical Society.

Abstract:

We report a new measurement of the cross section for the production of isolated photons with transverse energies (E Tγ) above 10 GeV and pseudorapidities |η| < 2.5 in p̄ collisions at √s = 1.8 TeV. The results are based on a data sample of 107.6 pb -1 recorded during 1992-1995 with the D0 detector at the Fermilab Tevatron collider. The background, predominantly from jets which fragment to neutral mesons, was estimated using the longitudinal shower shape of photon candidates in the calorimeter. The measured cross section is in good agreement with the next-to-leading order QCD calculation for E Tγ ≳ 36 GeV. © 2000 The American Physical Society.

Abstract:

The lateral and longitudinal profiles of hadronic showers detected by a prototype of the ATLAS Iron-Scintillator Tile Hadron Calorimeter have been investigated. This calorimeter presents a unique longitudinal configuration of scintillator tiles. Using a fine-grained pion beam scan at 100 GeV, a detailed picture of transverse shower behaviour is obtained. The underlying radial energy densities for the four depth segments and for the entire calorimeter have been reconstructed. A three-dimensional hadronic shower parametrization has been developed. The results presented here are useful for understanding the performance of iron-scintillator calorimeters, for developing fast simulations of hadronic showers, for many calorimetry problems requiring the integration of a shower energy deposition in a volume and for future calorimeters design.