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Jen-Chieh Peng

Flavor Structure of the Nucleon and W - Production. Jen-Chieh Peng. University of Illinois. Workshop on “Parity-Violating Spin Asymmetries at RHIC” RIKEN-BNL, April 26-27, 2007. Violation of the Gottfried Sum Rule. New Muon Collaboration (NMC) obtains. S G = 0.235 ± 0.026.

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Jen-Chieh Peng

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  1. Flavor Structure of the Nucleon and W - Production Jen-Chieh Peng University of Illinois Workshop on “Parity-Violating Spin Asymmetries at RHIC” RIKEN-BNL, April 26-27, 2007

  2. Violation of the Gottfried Sum Rule New Muon Collaboration (NMC) obtains SG = 0.235 ± 0.026 ( Significantly lower than 1/3 ! )

  3. Explanations for the violation of Gottfried Sum Rule: • Uncertain extrapolation for 0.0 < x < 0.004 (Can be studied at EIC) • Nuclear effects for deuteron • Charge-symmetry breaking • in the proton Need independent methods to check the asymmetry, and to measure its x-dependence !

  4. The Drell-Yan Process: The x-dependence of can be directly measured

  5. Fermilab E866 Measurements

  6. The valence quarks affect the Dirac vacuum and the quark-antiquark sea

  7. Spin and flavor are closely connected Meson Cloud Model Pauli Blocking Model A spin-up valence quark would inhibit the probability of generating a spin-down antiquark Instanton Model Chiral-Quark Soliton Model Statistical Model

  8. Peng, Eur. Phys. J. A18 (2003) 395

  9. J-PARC 50 GeV

  10. No nuclear effects ! No assumption of charge-symmetry ! Large Q2 scale !

  11. Peng and Jansen, Phys. Lett. B 354 (1995) 460

  12. Peng and Jansen, Phys. Lett. B 354 (1995) 460

  13. Using more recent PDFs R. Z. Yang and Peng (2007)

  14. 950 pb-1 integrated luminosity R. Z. Yang and Peng (2007)

  15. Charge Symmetry Violation in PDF?

  16. Charge Symmetry violation from MRST Global fits (Eur. Phys. J. C35, 325 (2004)) CSV for sea quarks CSV for valence quarks

  17. Comparison between MRST and quark-model calculation Charge symmetry violation for valence quarks MRST Quark-model Eur. Phys. J. C35, 325 (2004) (Rodionov, Thomas, Londergan)

  18. Charge symmetry violating Charge-symmetric (S. Yoon and Peng, 2006)

  19. Charge-symmetric Charge symmetry violating (S. Yoon and Peng, 2006)

  20. 800 pb-1 integrated luminosity Charge symmetry violating (S. Yoon and Peng, 2006) Charge-symmetric

  21. for large x SU(6) symmetry d/u →1/2 SZ = 0 dominance d/u→1/5 S = 0 dominance d/u→0

  22. Melnitchouk and Peng (PL B400 (1997) 220) CDF, hep-ex/0501023

  23. Melnitchouk and Peng (PL B400 (1997) 220)

  24. Summary • W-production at RHIC provides unique information on the flavor asymmetry of unpolarized parton distributions. • The connection between flavor and spin structure remains an interesting area to explore. • W-production can disentangle the charge-symmetry violation effects from the sea-quark flavor asymmetry effect. • More simulation studies are required.

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