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Shunzo Kumano High Energy Accelerator Research Organization (KEK)

Determination of nuclear PDFs in the EIC era (Status of NPDFs and our requests to EIC experimentalists). Shunzo Kumano High Energy Accelerator Research Organization (KEK) Graduate University for Advanced Studies (GUAS). Our nuclear PDF page http://research.kek.jp/people/kumanos/nuclp.html.

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Shunzo Kumano High Energy Accelerator Research Organization (KEK)

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  1. Determination of nuclear PDFs in the EIC era(Status of NPDFs and our requests to EIC experimentalists) Shunzo Kumano High Energy Accelerator Research Organization (KEK) Graduate University for Advanced Studies (GUAS) Our nuclear PDF page http://research.kek.jp/people/kumanos/nuclp.html Workshop on Physics at a High Energy Electron Ion Collider October 19 - 23, 2009, INT, Seattle, USA http://www.int.washington.edu/PROGRAMS/09-43w.html October 20, 2009

  2. Requested tasks (try to reply in the end of my talk) Physics case for a "stage-I" electron-ion collider (EIC): polarized 2-5 GeV electrons250 GeV polarized protons or 100 GeV/nucleon light and heavy ions. • What are the "headline" physics issues that could be addressed by a stage-I machine? • In which ways can it add to studies performed at Jlab 12 GeV and at RHIC? • What are the key processes, cross sections, kinematical regions, event rates? • What is the status of the required theoretical tools? • What are the machine and detector parameters required to meet these physics goals and to maximize the benefit for the high energy EIC?

  3. 500 A D NMC (F /F ) 2 2 F2 & Drell-Yan data for nuclei SLAC 100 EMC (GeV2) E665 BCDMS 2 HERMES Q 10 2 ) A A' NMC (F /F ) 2 2 E772/E886 DY 1 0.001 0.01 0.1 1 x Kinematics "stage-I" EIC: 2-5 GeV electron  100 (250) GeV nucleon Stage-I EIC coverage • Our requests: • • Accurate measurements of • Q2 dependence of F2A/ F2D. • • FLA measurements. • Accurate gluon distributions in nuclei!

  4. Contents Introduction • Motivations • Typical data for modifications in F2 and Drell-Yan 2. PDFs in the nucleon • A recent global analysis (just a brief explanation) 3. Determination of PDFs in nuclei • Recent global analyses Comparisons of various analysis results • Difficulty in determining gluon modifications 4. Summary

  5. Introduction

  6. Motivations for studying parton distribution functions To establish QCD Perturbative QCD • In principle, theoretically established in many processes. (There are still issues on small-x physics.) • Experimentally confirmed (unpolarized, polarised ?) Non-perturbative QCD (PDFs) • Theoretical models: Bag, Soliton, … (It is important that we have intuitive pictures of the nucleon.) • Lattice QCD Theoretical non-pQCD calculations are not accurate enough.  Determination of the PDFs from experimental data.

  7. (2) For discussing any high-energy reactions, accurate PDFs • are needed. •  origin of nucleon spin:quark- and gluon-spin contributions •  exotic events at large Q2:physics of beyond current framework •  heavy-ion reactions:quark-hadron matter •  neutrino oscillations: nuclear effects in n + 16O •  cosmology: ultra-high-energy cosmic rays

  8. Nuclear modifications of structure function F2 Anti-shadowing Fermi motion of the nucleon Nuclear binding (+ Nucleon modification) Shadowing

  9. Drell-Yan cross-section ratio is roughly equal to antiquark ratio. Drell-Yan and Antiquark Distributions The Fermilab E772 Drell-Yan data suggested that nuclear modification of antiquark distributions should be small in the region, x≈0.1.

  10. Recent Global Analysis for Parton Distribution Functions in the Nucleon J. Blümlein’s talk at this workshop

  11. Recent activities  uncertainties  NNLO  QED  s – s  charm for LHC Recent papers on unpolarized PDFs It is likely that I miss some papers! CTEQ(uncertainties) D. Stump (J. Pumplin) et al., Phys. Rev. D65 (2001) 14012 & 14013. (CTEQ6) D. Pumplin et al., JHEP, 0207 (2002) 012; 0506 (2005) 080; 0602 (2006) 032; 0702 (2007) 053; PRD78 (2008) 013004. (charm) PR D75 (2007) 054029; (strange)PRL 93 (2004) 041802; Eur. Phys. J. C40 (2005) 145; JHEP 0704 (2007) 089. GRV(GRV98) M. Glück, E. Reya, and A. Vogt, Eur. Phys. J. C5 (1998) 461. (GJR08) M. Glück, P. Jimenez-Delgado, and E. Reya, Eur. Phys. J. C53 (2008) 355. MRST A. D. Martin, R. G. Roberts, W. J. Stirling, and R. S. Thorne, (MRST2001, 2002, 20033) Eur. Phys. J. C23 (2002) 73; Eur. Phys. J. C28 (2003) 455; (theoretical errors) Eur. Phys. J. C35 (2004) 325; (2004) PL B604 (2004) 61; (QED) Eur. Phys. J. C39 (2005) 155; PL B636 (2006) 259; (2006) PRD73 (2006) 054019; PL B652 (2007) 292. (2009)Eur. Phys. J. C63 (2009) 189. Alekhin S. I. Alekhin, PRD68 (2003) 014002; D74 (2006) 054033. BB J. Blümlein and H. Böttcher, Nucl. Phys. B774 (2007) 182-207. S. Alekhin, J. Blumlein, S. Klein, S. Moch, arXiv:0908.2766 [hep-ph]. NNPDF S. Forte et al., JHEP 0205 (2002) 062; 0503 (2005) 080; 0703 (2007) 039. H1 C. Adloff et al., Eur. Phys. J. C 21 (2001) 33; C30 (2003) 1. ZEUS S. Chekanov et al., PRD67 (2003) 012007; Eur. Phys. J. C42 (2005) 1. Recent upgrades.

  12. Parton distribution functions are determined by fitting various experimental data.

  13. NuTeV CHORAS HERA Tevatron Recent improvements on data set NuTeV, CHORAS HERA Tevatron A. D. Martin, W. J. Stirling, R. S. Thorne, and G. Watt, Eur. Phys. J. C63 (2009) 189.

  14. MSTW-2008 A. D. Martin, W. J. Stirling, R. S. Thorne, and G. Watt, Eur. Phys. J. C63 (2009) 189. uv dv g

  15. Gluon distributions (MSTW) Large x Gluon distributions still have large uncertainties at small- and large-x regions. Small x Longitudinal structure function FL

  16. Determination of Nuclear Parton Distribution Functions

  17. Recent global analyses on nuclear PDFs It is likely that I miss some papers! • EPS09 • K. J. Eskola, H. Paukkunen, and C. A. Salgado, JHEP 04 (2009) 065. • Charged-lepton DIS, DY, p0 production in dAu. • SYKMOO08 • I. Schienbein, J. Y. Yu, C. Keppel, J. G. Morfin, F. I. Olness, • and J. F. Owens, Phys. Rev. D 77 (2008) 044013. • Neutrino DIS (only NuTeV data). • HKN07 • M. Hirai, S. Kumano, and T. -H. Nagai, Phys. Rev. C 76 (2007) 065207. • Charged-lepton DIS, DY. • DS04 • D. de Florian and R. Sassot, Phys. Rev. D 69 (2004) 074028. • Charged-lepton DIS, DY. See also L. Frankfurt, V. Guzey, and M. Strikman, Phys. Rev. D 71 (2005) 054001; S. A. Kulagin and R. Petti, Phys. Rev. D 76 (2007) 094023.

  18. Global nuclear PDF analysis

  19. Data set for nuclear PDF analyses HKN07, PRC 76 (2007) 065207. • Charged-lepton DIS, DY 0.005 < x < 0.8, 1 < Q2 < 113 GeV2 • p0 production from d-Au collision • Neutrino DIS (NuTeV/CCFR): 0.015 < x < 0.75 Analysis results: total c2 / d.o.f. (# of parameter) • EPS09: 0.80 (17) • HKN07: 1.21 (12) • DS06: 0.80 (18) • SYKMOO08-A: 1.37 [n data]

  20. Functional form of initial distributions at Q02

  21. Comparison with F2Ca/F2D & DYpCa/ DYpD data LO analysis NLO analysis (Rexp-Rtheo)/Rtheo at the same Q2 points R= F2Ca/F2D, DYpCa/ DYpD

  22. Q2 dependence The differences between LO and NLO become obvious only at small x. • Experimental data are not accurate enough to find the differences.  Determination of gluon distributions (NLO terms) is not possible. • The uncertainties become smaller in NLO at small x. Only NLO uncertainty bands are shown.

  23. Nuclear PDFs

  24. JLab • Factory MINARA HKN07 results and future experiments Fermilab J-PARC RHIC LHC EIC HKN07, PRC 76 (2007) 065207. Fermilab J-PARC GSI RHIC LHC EIC

  25. EPS09 HKN07 Valence Sea Gluon DS04 Comparison of nuclear PDFs Different analysis results are consistent with each other because they are roughly within uncertainty bands. Valence quark: Well determined except at small x. Antiquark: Determined at small x, Large uncertainties at medium and large x. Gluon: Large uncertainties in the whole-x region. EPS09 (K. J. Eskola et al.), JHEP 04 (2009) 065

  26. Why is it so difficultto determine nuclear gluon distributions?

  27. (from H1 and ZEUS, hep-ex/0502008) F2 data for the proton 500 A D NMC (F /F ) 2 2 F2 & Drell-Yan data for nuclei SLAC 100 EMC (GeV2) E665 BCDMS 2 HERMES Q 10 2 ) A A' NMC (F /F ) 2 2 E772/E886 DY 1 0.001 0.01 0.1 1 x Current nuclear data are kinematically limited. region of nuclear data

  28. Scaling violation and Gluon distributions dominant term at small x K. Prytz, PLB 311 (1993) 286. Q2 dependence of F2 is proportional to the gluon distribution. No experimental consensus of Q2 dependence!  gA(x) determination is difficult.

  29. Summary I Nuclear PDFs Valence quark: Well determined except at small x. Antiquark: Determined at small x, Large uncertainties at medium and large x. Gluon: Large uncertainties in the whole-x region The antiquark modifications at medium x should be clarified by Fermilab-P906 and other hadron-beam projects (J-PARC?).  EIC can contribute to determination of gluon shadowing at x~10–3.

  30. Summary II: Short reply to the requests "stage-I" EIC: 2-5 GeV electrons  250 GeV protons or 100 GeV/nucleon ions • What are the "headline" physics issues that could be addressed by a stage-I machine? Determination of gluon shadowing. • In which ways can it add to studies performed at Jlab 12 GeV and at RHIC? gA(x~10–3) cannot be determined at both facilities. (RHIC forward?) • What are the key processes, cross sections, kinematical regions, event rates? Accurate Q2 dependence measurements of F2A / F2D. FLA measurements, … • What is the status of the required theoretical tools? Theoretical tools (pQCD) are well established at NLO (even NNLO). There may be an issue of standard DGLAP evolution at small x. • What are the machine and detector parameters required to meet these physics goals and to maximize the benefit for the high energy EIC? ?

  31. The End The End

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