A first determination of parton distributions with theoretical uncertainties

Rabah Abdul Khalek; Richard D. Ball; Stefano Carrazza; Stefano Forte; Tommaso Giani; Zahari Kassabov; Emanuele R. Nocera; Rosalyn L. Pearson; Juan Rojo; Luca Rottoli; Maria Ubiali; Cameron Voisey; Michael Wilson

doi:10.1140/epjc/s10052-019-7364-5

A first determination of parton distributions with theoretical uncertainties

Rabah Abdul Khalek, Richard D. Ball, Stefano Carrazza, Stefano Forte^*, Tommaso Giani, Zahari Kassabov, Emanuele R. Nocera, Rosalyn L. Pearson, Juan Rojo, Luca Rottoli, Maria Ubiali, Cameron Voisey, Michael Wilson

^*Corresponding author for this work

(Astro)-Particles Physics

Research output: Contribution to Journal › Article › Academic › peer-review

Abstract

The parton distribution functions (PDFs) which characterize the structure of the proton are currently one of the dominant sources of uncertainty in the predictions for most processes measured at the Large Hadron Collider (LHC). Here we present the first extraction of the proton PDFs that accounts for the missing higher order uncertainty (MHOU) in the fixed-order QCD calculations used in PDF determinations. We demonstrate that the MHOU can be included as a contribution to the covariance matrix used for the PDF fit, and then introduce prescriptions for the computation of this covariance matrix using scale variations. We validate our results at next-to-leading order (NLO) by comparison to the known next order (NNLO) corrections. We then construct variants of the NNPDF3.1 NLO PDF set that include the effect of the MHOU, and assess their impact on the central values and uncertainties of the resulting PDFs.

Original language	English
Article number	838
Pages (from-to)	1-6
Number of pages	6
Journal	European Physical Journal C
Volume	79
Issue number	10
Early online date	10 Oct 2019
DOIs	https://doi.org/10.1140/epjc/s10052-019-7364-5
Publication status	Published - Oct 2019

Funding

R. D. B. is supported by the UK Science and Technology Facility Council through Grant ST/P000630/1.S. F. is supported by the European Research Council under the European Union’s Horizon 2020 research and innovation Programme (Grant agreement n.740006). T. G. is supported by The Scottish Funding Council, grant H14027. Z. K. is supported by the European Research Council Consolidator Grant “NNLOforLHC2”. E. R. N. is supported by the European Commission through the Marie Skłodowska-Curie Action ParDHonS_FFs.TMDs (Grant number 752748). R. L. P. and M. W. are supported by the STFC Grant ST/R504737/1. J. R. is supported by the European Research Council Starting Grant “PDF4BSM” and by the Netherlands Organization for Scientific Research (NWO). L. R. is supported by the European Research Council Starting Grant “REINVENT” (Grant number 714788). M. U. is partially supported by the STFC Grant ST/L000385/1 and funded by the Royal Society grants DH150088 and RGF/EA/180148. C. V. is supported by the STFC grant ST/R504671/1.

Funders	Funder number
Not added	ST/P000681/1
Marie Skłodowska-Curie Action ParDHonS_FFs
Horizon 2020 Framework Programme	683211, 714788, 740006
Science and Technology Facilities Council	ST/R504737/1, ST/P000630/1
Royal Society	DH150088, RGF/EA/180148, ST/R504671/1
Scottish Funding Council	H14027
European Commission	752748
European Research Council
Nederlandse Organisatie voor Wetenschappelijk Onderzoek	ST/L000385/1

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title = "A first determination of parton distributions with theoretical uncertainties",

abstract = "The parton distribution functions (PDFs) which characterize the structure of the proton are currently one of the dominant sources of uncertainty in the predictions for most processes measured at the Large Hadron Collider (LHC). Here we present the first extraction of the proton PDFs that accounts for the missing higher order uncertainty (MHOU) in the fixed-order QCD calculations used in PDF determinations. We demonstrate that the MHOU can be included as a contribution to the covariance matrix used for the PDF fit, and then introduce prescriptions for the computation of this covariance matrix using scale variations. We validate our results at next-to-leading order (NLO) by comparison to the known next order (NNLO) corrections. We then construct variants of the NNPDF3.1 NLO PDF set that include the effect of the MHOU, and assess their impact on the central values and uncertainties of the resulting PDFs.",

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AU - Carrazza, Stefano

AU - Forte, Stefano

AU - Giani, Tommaso

AU - Kassabov, Zahari

AU - Nocera, Emanuele R.

AU - Pearson, Rosalyn L.

AU - Rojo, Juan

AU - Rottoli, Luca

AU - Ubiali, Maria

AU - Voisey, Cameron

AU - Wilson, Michael

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AB - The parton distribution functions (PDFs) which characterize the structure of the proton are currently one of the dominant sources of uncertainty in the predictions for most processes measured at the Large Hadron Collider (LHC). Here we present the first extraction of the proton PDFs that accounts for the missing higher order uncertainty (MHOU) in the fixed-order QCD calculations used in PDF determinations. We demonstrate that the MHOU can be included as a contribution to the covariance matrix used for the PDF fit, and then introduce prescriptions for the computation of this covariance matrix using scale variations. We validate our results at next-to-leading order (NLO) by comparison to the known next order (NNLO) corrections. We then construct variants of the NNPDF3.1 NLO PDF set that include the effect of the MHOU, and assess their impact on the central values and uncertainties of the resulting PDFs.

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A first determination of parton distributions with theoretical uncertainties

Abstract

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