Abstract
Since its start of data taking, the LHC has provided an impressive wealth of information on the quark and gluon structure of the proton. Indeed, modern global analyses of parton distribution functions (PDFs) include a wide range of LHC measurements of processes such as the production of jets, electroweak gauge bosons, and top quark pairs. In this work, we assess the ultimate constraining power of LHC data on the PDFs that can be expected from the complete dataset, in particular after the High-Luminosity (HL) phase, starting in around 2025. The huge statistics of the HL-LHC, delivering {mathcal {L}}=3hbox { ab}^{-1} to ATLAS and CMS and {mathcal {L}}=0.3hbox { ab}^{-1} to LHCb, will lead to an extension of the kinematic coverage of PDF-sensitive measurements as well as to an improvement in their statistical and systematic uncertainties. Here we generate HL-LHC pseudo-data for different projections of the experimental uncertainties, and then quantify the resulting constraints on the PDF4LHC15 set by means of the Hessian profiling method. We find that HL-LHC measurements can reduce PDF uncertainties by up to a factor of 2 to 4 in comparison to state-of-the-art fits, leading to few-percent uncertainties for important observables such as the Higgs boson transverse momentum distribution via gluon-fusion. Our results illustrate the significant improvement in the precision of PDF fits achievable from hadron collider data alone, and motivate the continuation of the ongoing successful program of PDF-sensitive measurements by the LHC collaborations.
Highlights
The recent breakthroughs in the calculation of NNLO QCD and next–to–leading order (NLO) QED and electroweak corrections to most parton distribution functions (PDFs)–sensitive processes have been instrumental in allowing for the full exploitation of the information provided by the LHC measurements
We show that our projections for the PDF error reduction, which are predominantly driven by the increased statistics of the High Luminosity (HL)–LHC data sample, depend only moderately on the specific scenario adopted for the reduction of the experimental systematic errors
We have quantified the expected constraints that precision HL–LHC measurements will impose on the quark and gluon structure of the proton
Summary
We present the PDF–sensitive processes for which HL–LHC pseudo–data have been generated, provide details about the binning and kinematic cuts, and describe the baseline Run I and II measurements that are used to model the experimental systematic uncertainties expected in the HL–LHC era
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