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.Commissioning of the ATLAS Muon Spectrometer with cosmic rays
European Physical Journal C 70:3 (2010) 875-916
Abstract:
The ATLAS detector at the Large Hadron Collider has collected several hundred million cosmic ray events during 2008 and 2009. These data were used to commission the Muon Spectrometer and to study the performance of the trigger and tracking chambers, their alignment, the detector control system, the data acquisition and the analysis programs. We present the performance in the relevant parameters that determine the quality of the muon measurement. We discuss the single element efficiency, resolution and noise rates, the calibration method of the detector response and of the alignment system, the track reconstruction efficiency and the momentum measurement. The results show that the detector is close to the design performance and that the Muon Spectrometer is ready to detect muons produced in high energy proton-proton collisions. © 2010 CERN for the benefit of the ATLAS collaboration.HERAPDF fits including F2(charm) data
Proceedings of Science (2010)
Abstract:
PDF fits in the HERAPDF1.0 formalism have been made to the combined HERA-I inclusive data and the combined F2(charm) data from the H1 and ZEUS experiments. The charm data are found to be sensitive to the value of the charm mass and the choice of the heavy quark scheme. This has consequences for the predictions of W and Z cross-sections at the LHC. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial- ShareAlike Licence.Inclusive dijet cross sections in neutral current deep inelastic scattering at HERA
European Physical Journal C 70:4 (2010) 965-982
Abstract:
Single- and double-differential inclusive dijet cross sections in neutral current deep inelastic ep scattering have been measured with the ZEUS detector using an integrated luminosity of 374 pb-1. The measurement was performed at large values of the photon virtuality, Q2, between 125 and 20 000 GeV2. The jets were reconstructed with the kT cluster algorithm in the Breit reference frame and selected by requiring their transverse energies in the Breit frame, ET,Bjet, to be larger than 8 GeV. In addition, the invariant mass of the dijet system, Mjj, was required to be greater than 20 GeV. The cross sections are described by the predictions of next-to-leading-order QCD. © 2010 The Author(s).Measurement of high-Q2 charged current deep inelastic scattering cross sections with a longitudinally polarised positron beam at HERA
European Physical Journal C 70:4 (2010) 945-963