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Enhanced threshold resummation formalism for lepton pair production and its effects in the determination of parton distribution functions

David Westmark and J. F. Owens
Phys. Rev. D 95, 056024 – Published 31 March 2017
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  • INTRODUCTION
  • THRESHOLD RESUMMATION
  • RESUMMATION IN DIS AND LPP
  • PDF FITS USING RESUMMATION: COSINE AND…
  • ENHANCED RESUMMATION
  • CONCLUSIONS
    • References

    Abstract

    We demonstrate that theoretical predictions using current resummation techniques for the lepton pair production (LPP) rapidity and xF distributions can be inconsistent with data in high rapidity and xF kinematic regions by observing their effect in global fits of parton distribution functions (PDFs). We present an enhanced resummation technique for the LPP rapidity and xF distributions that agrees with LPP data. The enhanced resummation method is used in conjunction with threshold resummation in deep inelastic scattering to perform two global fits of PDFs using the minimal and Borel prescriptions. The results are analyzed to determine the effect of threshold resummation on global fits of PDFs.

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    • Received 21 February 2017

    DOI:https://doi.org/10.1103/PhysRevD.95.056024

    © 2017 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Deep inelastic scatteringHadron-hadron interactionsResummation methods
    1. Physical Systems
    NeutronsProtonsQuark model
    Particles & FieldsNuclear Physics

    Authors & Affiliations

    David Westmark

    • Tallahassee Community College, 444 Appleyard Drive, Tallahassee, Florida 32304, USA

    J. F. Owens

    • Florida State University, Tallahassee, Florida 32306-4350, USA

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    Issue

    Vol. 95, Iss. 5 — 1 March 2017

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    Images

    • Figure 1
      Figure 1

      A plot demonstrating resummation effects for F2 at Q2=24.5  GeV2 in electron-proton DIS. (Upper panel) NLO (solid line), NLO+NLL using MP (dashed line), and NLO+NLL using BP (dotted line) curves in a semilog plot. (Lower panel) The same curves normalized to NLO.

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    • Figure 2
      Figure 2

      A plot demonstrating the resummation effects on the proton-proton LPP xF distribution at Q=7.95  GeV and s=38.75  GeV. The curves depict the calculations at NLO (solid), NLO+NLL using MP (dashed) and NLO+NLL using BP (fine dashed) with the cosine method, and NLO+NLL using MP (dotted) and NLO+NLL using BP (dot-dashed) with the expansion method, all normalized to NLO.

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    • Figure 3
      Figure 3

      A plot of data points from the E866 proton-proton data at s=38.75  GeV and Q>5.7  GeV, with statistical and systematic errors added in quadrature. Note that some data points with exceptionally large uncertainties or that vary greatly from the other data have been excluded from the plot for the sake of aiding in visualization. The data have been normalized to a NLO+NLL calculation using the MP and cosine methods with the PDFs determined in the corresponding fit. Note that the NLO+NLL calculation was shifted by the normalization parameter from the fit, which resulted in an approximately 30% reduction. The high χ2 is demonstrated by the fact that the resummed curve lies well above the data points at highest xF, some of which have relatively small uncertainties.

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    • Figure 4
      Figure 4

      A plot showing the resummation corrections to the LPP xF distribution using the enhanced resummation formalism. The curves for NLO (solid), NLO+NLL using the MP and expansion method (dashed), NLO+NLL using the BP and expansion method (dotted), and NLO+NLL using the enhanced resummation formalism for both MP (fine dashed) and BP (dot-dashed) are all calculated at Q=7.95  GeV using CJ12min PDFs and are normalized to NLO.

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    • Figure 5
      Figure 5

      A comparison of the shapes of the up and down quark distributions from the CJ12min PDFs to the two fitted PDF sets at Q2=100  GeV2. Both distributions are shown normalized to the CJ12min PDFs, which act as the reference set of PDFs.

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