Uncertainties due to Nuclear Data in Proton PDF Fits

Pearson, Rosalyn L.; Ball, Richard D.; Nocera, Emanuele R.

doi:10.22323/1.352.0027

“…The theory covariance matrix formalism was first applied to the incorporation of nuclear uncertainties in PDF fits, firstly to data taken on heavy nuclear targets [365,366], then to data taken on deuteron targets [104,367]. The prior in these examples was determined empirically, through fits to nuclear data.…”

Section: B Theoretical Uncertainties In Pdf Fitsmentioning

confidence: 99%

Snowmass 2021 whitepaper: Proton structure at the precision frontier

Amoroso,

Apyan,

Armesto

et al. 2022

Preprint

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An overwhelming number of theoretical predictions for hadron colliders require parton distribution functions (PDFs), which are an important ingredient of theory infrastructure for the next generation of high-energy experiments. This whitepaper summarizes the status and future prospects for determination of high-precision PDFs applicable in a wide range of energies and experiments, in particular in precision tests of the Standard Model and in new physics searches at the high-luminosity Large Hadron Collider and Electron-Ion Collider. We discuss the envisioned advancements in experimental measurements, QCD theory, global analysis methodology, and computing that are necessary to bring unpolarized PDFs in the nucleon to the N2LO and N3LO accuracy in the QCD coupling strength. Special attention is given to the new tasks that emerge in the era of the precision PDF analysis, such as those focusing on the robust control of systematic factors both in experimental measurements and theoretical computations. Various synergies between experimental and theoretical studies of the hadron structure are explored, including opportunities for studying PDFs for nuclear and meson targets, PDFs with electroweak contributions or dependence on the transverse momentum, for incisive comparisons between phenomenological models for the PDFs and computations on discrete lattice, and for cross-fertilization with machine learning/AI approaches.

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“…The theory covariance matrix formalism was first applied to incorporate nuclear uncertainties in PDF fits, firstly to data taken on heavy nuclear targets [382,383], then to data taken on deuteron targets [117,384]. The prior in these examples was determined empirically, through fits to nuclear data.…”

Section: Theoretical Uncertainties In Pdf Fitsmentioning

confidence: 99%

Snowmass 2021 Whitepaper: Proton Structure at the Precision Frontier

Amoroso¹,

Apyan²,

Armesto³

et al. 2022

View full text Add to dashboard Cite

An overwhelming number of theoretical predictions for hadron colliders require parton distribution functions (PDFs), which are an important ingredient of theory infrastructure for the next generation of high-energy experiments. This whitepaper summarizes the status and future prospects for determination of high-precision PDFs applicable in a wide range of energies and experiments, in particular in precision tests of the Standard Model and in new physics searches at the high-luminosity Large Hadron Collider and Electron-Ion Collider. We discuss the envisioned advancements in experimental measurements, QCD theory, global analysis methodology, and computing that are necessary to bring unpolarized PDFs in the nucleon to the N2LO and N3LO accuracy in the QCD coupling strength. Special attention is given to the new tasks that emerge in the era of the precision PDF analysis, such as those focusing on the robust control of systematic factors both in experimental measurements and theoretical computations. Various synergies between experimental and theoretical studies of the hadron structure are explored, including opportunities for studying PDFs for nuclear and meson targets, PDFs with electroweak contributions or dependence on the transverse momentum, for incisive comparisons between phenomenological models for the PDFs and computations on discrete lattice, and for cross-fertilization with machine learning/AI approaches.

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Parton distributions with scale uncertainties: a Monte Carlo sampling approach

Kassabov

¹

,

Ubiali

²

,

Voisey

³

2023

J. High Energ. Phys.

6

0

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We present the MCscales approach for incorporating scale uncertainties in parton distribution functions (PDFs). The new methodology builds on the Monte Carlo sampling for propagating experimental uncertainties into the PDF space that underlies the NNPDF approach, but it extends it to the space of factorisation and renomalisation scales. A prior probability is assigned to each scale combinations set in the theoretical predictions used to obtain each PDF replica in the Monte Carlo ensemble and a posterior probability is obtained by selecting replicas that satisfy fit-quality criteria. Our approach allows one to exactly match the scale variations in the PDFs with those in the computation of the partonic cross sections, thus accounting for the full correlations between the two. We illustrate the opportunities for phenomenological exploration made possible by our methodology for a variety of LHC observables. Sets of PDFs enriched with scale information are provided, along with a set of tools to use them.

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Uncertainties due to Nuclear Data in Proton PDF Fits

Cited by 3 publications

References 20 publications

Snowmass 2021 whitepaper: Proton structure at the precision frontier

Snowmass 2021 whitepaper: Proton structure at the precision frontier

Snowmass 2021 Whitepaper: Proton Structure at the Precision Frontier

Parton distributions with scale uncertainties: a Monte Carlo sampling approach

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