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Parton

About: Parton is a research topic. Over the lifetime, 13484 publications have been published within this topic receiving 368877 citations.


Papers
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Journal ArticleDOI
TL;DR: The MSHT20 set of parton distribution functions (PDFs) of the proton, determined from global analyses of the available hard scattering data, were made available at NNLO, NLO, and LO as mentioned in this paper.
Abstract: We present the new MSHT20 set of parton distribution functions (PDFs) of the proton, determined from global analyses of the available hard scattering data. The PDFs are made available at NNLO, NLO, and LO, and supersede the MMHT14 sets. They are obtained using the same basic framework, but the parameterisation is now adapted and extended, and there are 32 pairs of eigenvector PDFs. We also include a large number of new data sets: from the final HERA combined data on total and heavy flavour structure functions, to final Tevatron data, and in particular a significant number of new LHC 7 and 8 TeV data sets on vector boson production, inclusive jets and top quark distributions. We include up to NNLO QCD corrections for all data sets that play a major role in the fit, and NLO EW corrections where relevant. We find that these updates have an important impact on the PDFs, and for the first time the NNLO fit is strongly favoured over the NLO, reflecting the wider range and in particular increased precision of data included in the fit. There are some changes to central values and a significant reduction in the uncertainties of the PDFs in many, though not all, cases. Nonetheless, the PDFs and the resulting predictions are generally within one standard deviation of the MMHT14 results. The major changes are the $u-d$ valence quark difference at small $x$, due to the improved parameterisation and new precise data, the $\bar d, \bar u$ difference at small $x$, due to a much improved parameterisation, and the strange quark PDF due to the effect of LHC $W,Z$ data and inclusion of new NNLO corrections for dimuon production in neutrino DIS. We discuss the phenomenological impact of our results, and in general find reduced uncertainties in predictions for processes such as Higgs, top quark pair and $W,Z$ production at post LHC Run-II energies.

125 citations

Journal ArticleDOI
TL;DR: In this paper, the HERA measurements of the proton structure function at small x allow the opportunity to improve our knowledge of the gluon and quark distribution functions, and they perform a global analysis which incorporates these new precise data, and which extends down to Q 2 = 1.5 GeV2.

125 citations

Journal ArticleDOI
TL;DR: In this paper, exact expressions for the matrix elements of the parton process relevant for jet production in e+e−, γγ, e−P and P P collisions are derived.

124 citations

Journal ArticleDOI
TL;DR: In this article, the authors provide an overview of the present knowledge of the nucleon spin structure and give an outlook on future experiments, focusing in particular on the spin structure functions g 1 and g 2 of the nucleus and their moments.

124 citations

Journal ArticleDOI
TL;DR: A simple extrapolation formula for the moments of the nonsinglet quark distribution u-d, as a function of quark mass, is proposed, which embodies the general constraints imposed by the chiral symmetry of QCD.
Abstract: We present the resolution of a long-standing discrepancy between the moments of parton distributions calculated from lattice QCD and their experimental values. We propose a simple extrapolation formula for the moments of the nonsinglet quark distribution u-d, as a function of quark mass, which embodies the general constraints imposed by the chiral symmetry of QCD. The inclusion of the leading nonanalytic behavior leads to an excellent description of both the lattice data and the experimental values of the moments.

124 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023384
2022897
2021410
2020423
2019472
2018424