1 Probing Spin and Flavor Structures of the Nucleon with Hadron Beams Flavor and spin structures of the nucleons –Overview and recent results Future prospects –Fermilab, RHIC, J-PARC Jen-Chieh Peng Workshop on Hadron Physics in China and Opportunities with 12 GeV JLab Lanzhou University, July 31-August 1, 2009 University of Illinois Outline

2 Flavor and spin structures of the nucleons 99.97% of the visible mass of the Universe is composed of protons and neutrons Quantum Chromodynamics (QCD) at the confinement scale remains to be understood The progress of lattice QCD calculations allow direct comparison between the experiments and theory They provide crucial inputs for describing hard processes in high energy collisions such as at LHC (p+p collider) Why is it interesting?

3 Electron beam as a powerful tool for probing partonic structure in nucleon SLAC e p  e’ X (DIS) DIS data vs. QCD calculation

4 Some open questions on nucleon partonic structures What are the flavor structures of valence and sea quarks? What are the origins of sea quarks in nucleons and nuclei? Where does the proton’s spin come from? How are the quark’s transverse spin distributions different from the helicity distributions? What are the characteristics of various transverse- momentum-dependent (TMD) quark distribution functions?

5 Flavor structure of the parton distributions in the proton

6 Complimentality between DIS and Drell-Yan Both DIS and Drell-Yan process are tools to probe the quark and antiquark structure in hadrons DIS Drell-Yan

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9 Meson cloud model Thomas / Brodsky and Ma Analysis of neutrino DIS data NuTeV, PRL 99 (2007)

10 Predictions for sea-quark polarizations Meson Cloud Model Chiral-Quark Soliton Model Remain to be tested …..

11 J-PARC 50 GeV

12 Fermilab E906 dimuon experiment (expected to run ~ )

13 No nuclear effects No assumption of charge-symmetry Large Q 2 scale

14 Using recent PDFs R. Z. Yang and JCP arXiv

15 Charge Symmetry Violation in PDF? See recent review of Londergan, Peng, and Thomas (arXiv: )

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 MRSTQuark-model (Rodionov, Thomas, Londergan)Eur. Phys. J. C35, 325 (2004)

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

19 Gluon distributions in proton versus neutron? Lingyan Zhu et al., PRL, 100 (2008) (arXiv: ) Gluon distributions in proton and neutron are very similar

20 Three parton distributions describing quark’s transverse momentum and/or transverse spin 1) Transversity 2) Sivers function 3) Boer-Mulders function

21 Unpolarized Polarized target Polarzied beam and target S L and S T : Target Polarizations; λe: Beam Polarization Sivers Transversity Boer-Mulders Transversity and TMD PDFs are probed in Semi-Inclusive DIS

22 Transversity and TMD PDFs are also probed in Drell-Yan

23 Boer-Mulders function h 1 ┴ Boer, PRD 60 (1999) ● Observation of large cos(2Φ) dependence in Drell-Yan with pion beam ● How about Drell-Yan with proton beam? 252 GeV/c π + W

24 cos2Φ Distribution in p+p and p+d Drell-Yan E866 Collab., Lingyan Zhu et al., PRL 99 (2007) ; PRL 102 (2009) Sea-quark BM functions are much smaller than valence BM

25 Polarized Drell-Yan with polarized proton beam? Polarized Drell-Yan experiments have never been done before Provide unique information on the quark (antiquark) spin Quark helicity distribution Quark transversity distribution Can be measured at RHIC, J-PARC, FAIR etc.

26 Does Sivers function change sign between DIS and Drell-Yan? Does Boer-Mulders function change sign between DIS and Drell-Yan? Are all Boer-Mulders functions alike (proton versus pion Boer-Mulders functions) Flavor dependence of TMD functions Independent measurement of transversity with Drell-Yan Outstanding questions in TMD to be addressed by future Drell-Yan experiments

27 Future prospect for Drell-Yan experiments Fermilab p+p, p+d, p+A –Unpolarized beam and target RHIC –Polarized p+p collision COMPASS –π-p and π-d with polarized targets FAIR –Polarized antiproton-proton collision J-PARC –Possibly polarizied proton beam and target

28 Summary The Deep-Inelastic Scattering, together with Drell-Yan process in hadron collisions, have provide much information (and surprises) on the partonic structures of the hadrons New Drell-Yan (and W-production) experiments using pion, proton, and antiproton beams will further elucidate the flavor and spin structures of the nucleons.

29 Double-spin asymmetry in polarized p-p at J-PARC 1) Double-spin asymmetry (A LL ) with longitudinally polarized beam/target in Drell-Yan probe Quark helicity distributions 2) Double-spin asymmetry (A TT ) with transversely polarized beam/target in Drell-Yan probe quark transversity distribution P24 proposal, Goto et al.

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

31 Leading-Twist Quark Distributions No K ┴ dependence K ┴ - dependent, T-odd K ┴ - dependent, T-even ( A total of eight distributions)

32 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

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