ATLAS

Abstract:

The key elements of the Muon Ionization Cooling Experiment (MICE) [1] cooling channel are the absorbers that are a part of the MICE absorber focus coil modules (AFC modules). The boundaries of room temperature solid absorbers are well defined. The density of most solid absorber materials is also well understood. The properties of solid absorber are most certainly understood to 0.3 percent. The MICE liquid absorbers are different in that their dimensions are a function of the absorber temperature and the fluid pressure within the absorber. The second element in the liquid absorber is the variability of the liquid density with temperature and pressure. While one can determine the absorber boundary within 0.3 percent, the determination of the liquid density within 0.3 percent is more difficult (particularly with liquid helium in the absorber). This report presents a method of calculating absorber boundary and the cooling performance of the MICE absorbers as a function of fluid temperature and pressure.

Abstract:

We report results of a study of the Bs0 oscillation frequency using a large sample of Bs0 semileptonic decays corresponding to approximately 1fb-1 of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider in 2002-2006. The amplitude method gives a lower limit on the Bs0 oscillation frequency at 14.8ps-1 at the 95% C.L. At Δms=19ps-1, the amplitude deviates from the hypothesis A=0 (1) by 2.5 (1.6) standard deviations, corresponding to a two-sided C.L. of 1% (10%). A likelihood scan over the oscillation frequency, Δms, gives a most probable value of 19ps-1 and a range of 17<Δms<21ps-1 at the 90% C.L., assuming Gaussian uncertainties. This is the first direct two-sided bound measured by a single experiment. If Δms lies above 22ps-1, then the probability that it would produce a likelihood minimum similar to the one observed in the interval 16-22ps-1 is (5.0±0.3)%. © 2006 The American Physical Society.

Abstract:

We search for pair-produced Dirac magnetic monopoles in 35.7pb-1 of proton-antiproton collisions at s=1.96TeV with the Collider Detector at Fermilab (CDF). We find no monopole candidates corresponding to a 95% confidence-level cross-section limit σ<0.2pb for a monopole with mass between 200 and 700GeV/c2. Assuming a Drell-Yan pair-production mechanism, we set a mass limit m>360GeV/c2. © 2006 The American Physical Society.

Abstract:

We report the first evidence for a fully reconstructed decay mode of the Bc± meson in the channel Bc±→J/ψπ±, with J/ψ→μ+μ-. The analysis is based on an integrated luminosity of 360pb-1 in pp̄ collisions at 1.96 TeV center of mass energy collected by the Collider Detector at Fermilab. We observe 14.6±4.6 signal events with a background of 7.1±0.9 events, and a fit to the J/ψπ± mass spectrum yields a Bc± mass of 6285.7±5.3(stat)±1. 2(syst)MeV/c2. The probability of a peak of this magnitude occurring by random fluctuation in the search region is estimated as 0.012%. © 2006 The American Physical Society.

Abstract:

The GridPP Collaboration is building a UK computing Grid for particle physics, as part of the international effort towards computing for the Large Hadron Collider. The project, funded by the UK Particle Physics and Astronomy Research Council (PPARC), began in September 2001 and completed its first phase 3 years later. GridPP is a collaboration of approximately 100 researchers in 19 UK university particle physics groups, the Council for the Central Laboratory of the Research Councils and CERN, reflecting the strategic importance of the project. In collaboration with other European and US efforts, the first phase of the project demonstrated the feasibility of developing, deploying and operating a Grid-based computing system to meet the UK needs of the Large Hadron Collider experiments. This note describes the work undertaken to achieve this goal. © 2006 IOP Publishing Ltd.