Towards ultimate parton distributions at the high-luminosity LHC

Rabah Abdul Khalek, Shaun Bailey, Jun Gao, Lucian Harland-Lang, Juan Rojo*

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


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 L=3ab-1 to ATLAS and CMS and L=0.3ab-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.

Original languageEnglish
Article number962
Pages (from-to)1-25
Number of pages25
JournalEuropean Physical Journal C
Issue number11
Early online date22 Nov 2018
Publication statusPublished - Nov 2018


Acknowledgements We are grateful to W. Barter, M. Campanelli, C. Gwenlan, S. Farry, and K. Lipka for discussion about the projections of future HL–LHC measurements at ATLAS, CMS, and LHCb. We thank P. Starovoitov for providing the APPLgrids for the inclusive jet measurements at the HL–LHC. R. A. K. and J. R. are supported by the European Research Council (ERC) Starting Grant “PDF4BSM” and by the Dutch Organization for Scientific Research (NWO). The work of J. G. is sponsored by Shanghai Pujiang Program and by the National Natural Science Fundation of China under the Grant No. 11875189. S. B. is supported by the Science and Technology Facilities Council (STFC). L. H. L thanks the Science and Technology Facilities Council (STFC) for support via grant award ST/L000377/1.

FundersFunder number
Dutch Organization for Scientific Research
National Natural Science Fundation of China11875189
Shanghai Pujiang Program
Seventh Framework Programme335260
Science and Technology Facilities CouncilST/L000377/1
European Research Council
Nederlandse Organisatie voor Wetenschappelijk Onderzoek


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