Direct top-quark width measurement at CDF.
Phys Rev Lett 105:23 (2010) 232003
Abstract:
We present a measurement of the top-quark width in the lepton+jets decay channel of tt events produced in p p collisions at Fermilab's Tevatron collider and collected by the CDF II detector. From a data sample corresponding to 4.3 fb(-1) of integrated luminosity, we identify 756 candidate events. The top-quark mass and the mass of the hadronically decaying W boson that comes from the top-quark decay are reconstructed for each event and compared with templates of different top-quark widths (Γ(t)) and deviations from nominal jet energy scale (Δ(JES)) to perform a simultaneous fit for both parameters, where Δ(JES) is used for the in situ calibration of the jet energy scale. By applying a Feldman-Cousins approach, we establish an upper limit at 95% confidence level (CL) of Γ(t) <7.6 GeV and a two-sided 68% CL interval of 0.3 GeV <Γ(t) <4.4 GeV for a top-quark mass of 172.5 GeV/c(2), which are consistent with the standard model prediction.Direct top-quark width measurement at CDF
Physical Review Letters 105:23 (2010)
Abstract:
We present a measurement of the top-quark width in the lepton+jets decay channel of tt̄ events produced in pp̄ collisions at Fermilab's Tevatron collider and collected by the CDF II detector. From a data sample corresponding to 4.3fb⊃-1 of integrated luminosity, we identify 756 candidate events. The top-quark mass and the mass of the hadronically decaying W boson that comes from the top-quark decay are reconstructed for each event and compared with templates of different top-quark widths (Γt) and deviations from nominal jet energy scale (ΔJES) to perform a simultaneous fit for both parameters, where ΔJES is used for the in situ calibration of the jet energy scale. By applying a Feldman-Cousins approach, we establish an upper limit at 95% confidence level (CL) of Γt<7.6GeV and a two-sided 68% CL interval of 0.3GeV<Γt<4.4GeV for a top-quark mass of 172.5GeV/c2, which are consistent with the standard model prediction. © 2010 The American Physical Society.Measurement of underlying event characteristics using charged particles in pp collisions at $\sqrt{s} = 900 GeV$ and 7 TeV with the ATLAS detector
ArXiv 1012.0791 (2010)
A posteriori inclusion of PDFs in NLO QCD final-state calculations: The APPLGRID Project
Proceedings of Science (2010)
Abstract:
The calculation of cross-sections at Next-to-Leading order in QCD involves the integration over the final state phase space in order to cancel the infra-red divergences. For the calculation of cross sections for jet observables in deep-inelastic scattering or at hadron-hadron colliders this integration requires the Monte Carlo generation of a large number of event weights, and must be repeated for any calculation with a different choice of parton densities within the proton or different choice of factorisation or renormalisation scale. This makes the full calculation with many of the available parton density function error sets, or any iterative fit of the parton densities themselves, prohibitive in terms of the processing time required. A method for the a posteriori inclusion of the parton densities in the calculation is presented. In this method, the Monte Carlo weights from the integration over the hard-subprocess phase space are stored in a look-up table so that the full calculation need be performed only once, after which the cross section can be obtained with any parton density set by a fast convolution with the stored weights. A detailed example from inclusive jet production at the LHC is presented. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.A probabilistic approach to modelling spatial language with its application to sensor models
CEUR Workshop Proceedings 620 (2010) 1-8