The PDF4LHC Working Group Interim Recommendations

Abstract

This note provides an interim summary of the current recommendations of the PDF4LHC working group for the use of parton distribution functions (PDFs) and of PDF uncertainties at the LHC, for cross section and cross section uncertainty calculations. It also contains a succinct user guide to the computation of PDFs, uncertainties and correlations using available PDF sets.A companion note (the PDF4LHC Working Group Interim Report) summarizes predictions for benchmark cross sections at the LHC at NLO using modern PDFs currently available from 6 PDF fitting groups.

Search for the Standard Model Higgs boson in the decay channel H->ZZ(*)->4l with 4.8 fb-1 of pp collision data at sqrt(s) = 7 TeV with ATLAS

“…The uncertainty in the production cross section due to the choice of QCD scale is +12 −8 % for the gluon fusion process, and ±1% for the vector-boson fusion, associated W H production, and associated ZH production processes [34]. The uncertainty in the production cross section due to the parton distribution function (PDF) and α s is ±8% for gluon-initiated process and ±4% for quarkinitiated processes [55][56][57][58][59]. The Higgs boson decay branching ratio to the four-lepton final state is predicted by prophecy4f [31,32], which includes the complete NLO QCD+EW corrections, interference effects between identical final-state fermions, and leading two-loop heavy Higgs boson corrections to the four-fermion width.…”

PDFs and Top Physics

“…The improved agreement of the global PDF sets and the means of combining them in a more statistically robust fashion allows for an update in the previous PDF4LHC prescription [21] for combining PDFs when a single prediction representing a reasonable average prediction and quite conservative uncertainty is required. The sets entering into the combination must satisfy requirements, i.e.…”

Search for the Standard Model Higgs boson in the decay channel H->ZZ(*)->4l with the ATLAS detector

“…The theoretical uncertainties on the Higgs boson production cross section are 15-20% for the gluon fusion process and 3-9% for the vector-boson fusion process [17], depending on the Higgs boson mass 2 . They include uncertainties on the QCD scale and on the parton distribution functions [46][47][48][49]. An additional 2% uncertainty is added to the signal selection efficiency due to the modelling of the signal kinematics.…”