Nuclear uncertainties in the determination of proton PDFs

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

doi:10.1140/epjc/s10052-019-6793-5

Cited by 34 publications

(45 citation statements)

References 142 publications

(264 reference statements)

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“…Even with constraints from related processes such as gauge boson production at the Tevatron and the LHC, information provided by neutrino-induced charged current deep-inelastic scattering on heavy nuclear targets play a critical role in disentangling the proton's quark and antiquark distributions. However, given the current precision of proton PDF fits, neglecting the nuclear uncertainties associated with neutrino-nucleus scattering may not be well justified anymore [11], as opposed to the situation some years ago [12].…”

Section: Introductionmentioning

confidence: 99%

Nuclear parton distributions from lepton-nucleus scattering and the impact of an electron-ion collider

2019

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We present a first determination of the nuclear parton distribution functions (nPDF) based on the NNPDF methodology: nNNPDF1.0. This analysis is based on neutral-current deepinelastic structure function data and is performed up to NNLO in QCD calculations with heavy quark mass effects. For the first time in the NNPDF fits, the χ 2 minimization is achieved using stochastic gradient descent with reverse-mode automatic differentiation (backpropagation). We validate the robustness of the fitting methodology through closure tests, assess the perturbative stability of the resulting nPDFs, and compare them with other recent analyses. The nNNPDF1.0 distributions satisfy the boundary condition whereby the NNPDF3.1 proton PDF central values and uncertainties are reproduced at A = 1, which introduces important constraints particularly for low-A nuclei. We also investigate the information that would be provided by an Electron-Ion Collider (EIC), finding that EIC measurements would significantly constrain the nPDFs down to x 5 × 10 −4 . Our results represent the first-ever nPDF determination obtained using a Monte Carlo methodology consistent with that of state-of-the-art proton PDF fits, and provide the foundation for a subsequent global nPDF analyses including also proton-nucleus data.

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Section: Introductionmentioning

confidence: 99%

Nuclear parton distributions from lepton-nucleus scattering and the impact of an electron-ion collider

2019

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“…MHOUs are routinely estimated by varying the arbitrary renormalization μ r and factorization μ f scales of perturbative computations [1], though alternative methods have also been proposed [6][7][8]. Our inclusion of the MHOU in a PDF fit involves two steps: first we establish how theoretical uncertainties can be included in such a fit through a covariance matrix [9,10], and then we find a way of computing and validating the covariance matrix associated with the MHOU using scale variations [11]. By producing variants of NNPDF3.1 which include the MHOU, we are then able to finally address the long-standing question of their impact on state-of-the-art PDF sets.…”

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confidence: 99%

“…More details of the implementation of the theory covariance matrix in PDF fits may be found in Refs. [9,10]. The choice of nuisance parameters Δ (k) i used in Eq.…”

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A first determination of parton distributions with theoretical uncertainties

et al. 2019

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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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“…In these proceedings, we show how to use existing nuclear PDFs (nPDFs) to provide an estimate of nuclear uncertainties, and include them in future proton PDF fits within the Neural Network PDF (NNPDF) framework [4]. For a more detailed analysis, see [5].…”

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Uncertainties due to Nuclear Data in Proton PDF Fits

Pearson¹,

Ball²,

Nocera³

2019

Proceedings of XXVII International Workshop on Deep-Inelastic Scattering and Related Subjects — PoS(DIS2019)

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We investigate the role of uncertainties due to the use of nuclear data when determining proton parton distribution functions (PDFs), and show how these uncertainties can be included in fits. In particular, we assess data with nuclear targets included in NNPDF3.1, namely from CHORUS, NuTeV and E605 with Pb, Fe and Cu targets respectively. We then analyse the resulting form of the PDFs, noting that the increase in uncertainty is small. Finally, we consider the impact on thē d/ū ratio, total strangeness s +s and strange valence distribution s −s. We find the effects to be negligible in all cases.

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Nuclear uncertainties in the determination of proton PDFs

Cited by 34 publications

References 142 publications

Nuclear parton distributions from lepton-nucleus scattering and the impact of an electron-ion collider

Nuclear parton distributions from lepton-nucleus scattering and the impact of an electron-ion collider

A first determination of parton distributions with theoretical uncertainties

Uncertainties due to Nuclear Data in Proton PDF Fits

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