Abstract
In an earlier publication, we introduced the software package Error PDF Updating Method Package (epump) that can be used to update or optimize a set of parton distribution functions (PDFs), including the best-fit PDF set and Hessian eigenvector pairs of PDF sets (i.e., error PDFs), and to update any other set of observables, in the Hessian approach. Here, we validate the epump program with a detailed comparison against a full global analysis, and we demonstrate the potential of epump by presenting selected phenomenological applications relevant to the Large Hadron Collider. For example, we use the package to estimate the impact of the recent LHC data of the measurements of $W$ and $Z$ boson and top quark pair differential distributions on the CT14HERA2 PDFs.
Highlights
An understanding of uncertainties due to parton distribution functions (PDFs) is crucial to precision studies of the standard model as well as to searches for new physics beyond the standard model at hadron colliders, such as the CERN Large Hadron Collider
We introduced the software package Error PDF Updating Method Package that can be used to update or optimize a set of parton distribution functions (PDFs), including the best-fit PDF set and Hessian eigenvector pairs of PDF sets, and to update any other set of observables, in the Hessian approach
II C, we show, as an example, how to use Error PDF Updating Method Package (ePump) to directly update the theoretical predictions of the Higgs boson production cross section σðgg → hÞ from gluon fusion in the proton-proton collider, including its uncertainties induced by the updated error PDFs
Summary
An understanding of uncertainties due to parton distribution functions (PDFs) is crucial to precision studies of the standard model as well as to searches for new physics beyond the standard model at hadron colliders, such as the CERN Large Hadron Collider. We present more details of this check with jet data and present additional checks with deeply inelastic scattering (DIS) and Drell-Yan data In each of these cases, we will see that the updated PDFs obtained from ePump are very close to the global-fit results, i.e., CT14HERA2 PDFs in this case. We find a large impact on the quark PDFs, in the small-x region, when updated by adding the ATLAS 7 TeV W and Z data [6] This large deviation of the updated PDFs from the original CT14HERA2 PDFs suggests that the ePump result should only be trusted qualitatively in this case, and for quantitative results with this dataset, a full global fit is required.
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