Dr Elizabeth Gallas

Abstract:

A study of high energy muons traversing the ATLAS hadron Tile calorimeter in the barrel region in the energy range between 10 and 300 GeV is presented. Both test beam experimental data and Monte Carlo simulations are given and show good agreement. The Tile calorimeter capability of detecting isolated muons over the above energy range is demonstrated. A signal to background ratio of about 10 is expected for the nominal LHC luminosity (1034 1/cm2s). The photoelectron statistics effect in the muon shape response is shown. The e/mip ratio is found to be 0.81 ± 0.03; the e/μ ratio is in the range 0.91-0.97. The energy loss of a muon in the calorimeter, dominated by the energy lost in the absorber, can be correlated to the energy loss in the active material. This correlation allows one to correct on an event by event basis the muon energy loss in the calorimeter and therefore reduce the low energy tails in the muon momentum distribution.

Abstract:

The first combined test of an electromagnetic liquid argon accordion calorimeter and a hadronic scintillating-tile calorimeter was carried out at the CERN SPS. These devices are prototypes of the barrel calorimeter of the future ATLAS experiment at the LHC. The energy resolution of pions in the energy range from 20 to 300 GeV at an incident angle θ of about 11c is well-described by the expression σ/E = ((46.5 ± 6.0)%/√E + (1.2 ± 0.3)%) ⊗ (3.2 ± 0.4)GeV/E. Shower profiles, shower leakage, and the angular resolution of hadronic showers were also studied.

Abstract:

The energy loss spectrum of 150 GeV muons has been measured with a prototype of the ATLAS hadron calorimeter in the H8 beam of the CERN SPS. The differential probability dP/dυ per radiation length of a fractional energy loss υ = ΔEμ/Eμ has been measured in the range υ = 0.01 ÷ 0.95; it is compared with the theoretical predictions for energy losses due to bremsstrahlung and production of electron-positron pairs or of energetic knock-on electrons. The integrated probability ∫0.01^0.95(dP/dυ)dυ is (1.610 ± 0.015stat ±0 .105syst)·10^-3 in agreement with the theoretical predictions 1.556·10^-3 and 1.619·10^-3. Agreement with theory is also found in two intervals of υ where production of electron-positron pairs and knock-on electrons dominates. In the region of bremsstrahlung dominance (υ = 0.12 ÷ 0.95) the measured integrated probability (1.160 ± 0.040stat ± 0.075syst)·10^-4 is in agreement with the theoretical value of 1.185·10^-4, obtained using the Petrukhin and Shestakov description of the bremsstrahlung process. The same result is about 3.6 standard deviations (defined as the quadratic sum of statistical and systematic errors) lower than the theoretical prediction of 1.472·10^-4, obtained using Tsai's description of bremsstrahlung. © Springer-Verlag 1997.

Abstract:

We measure the top quark mass mt t¯t using pairs produced in the D0 detector by √s = 1.8 TeV p ¯p collisions in a 125pb^-1 exposure at the Fermilab Tevatron. We make a two constraint fit to mt in t¯t → b W⁺ ¯bW^- final states with one W decaying to q¯q and the other to ev or μ v. Events are binned in fit mass versus a measure of probability for events to be signal rather than background. Likelihood fits to the data yield mt = 17.3 ± 5.6 (stat) ± 6.2(syst) GeV/c². © 1998 The American Physical Society.

Abstract:

We present a measurement of the t¯t production cross section in p¯p collisions at √s=1.8TeV by the D0 experiment at the Fermilab Tevatron. The measurement is based on data from an integrated luminosity of approximately 125pb−1 accumulated during the 1992–1996 collider run. We observe 39 t¯t candidate events in the dilepton and lepton+jets decay channels with an expected background of 13.7 ± 2.2 events. For a top quark mass of 173.3 GeV/c2, we measure the t¯t production cross section to be 5.5 ± 1.8 pb. © 1997 The American Physical Society.