1. Large-X PDFs in the Drell-Yan Process
Jen-Chieh Peng
University of Illinois at Urbana-Champaign
“3rd International Workshop on Nucleon Structure at Large Bjorken X” Jefferson Lab, Newport News, Oct , 2010

2. Outline
• Complementarity between the DIS and the Drell-Yan process for probing parton distributions in nucleon and nuclei
Sea-quark distributions in the medium-X region with Drell-Yan and W-boson production
Parton distributions in nuclei with proton and pion induced Drell-Yan process
Charge-symmetry breaking of parton distributions with the W-boson production
Transverse-momentum-dependent parton distributions with the Drell-Yan process

3. Complimentality between DIS and Drell-Yan
McGaughey, Moss, JCP,
Ann.Rev.Nucl. Part. Sci. 49 (1999) 217
Both DIS and Drell-Yan process are tools to probe the quark and antiquark structure in hadrons (factorization, universality) 3

4. Lepton-pair production provides unique information on parton distributions
Probe antiquark distribution in nucleon
Probe antiquark distribution in pion
Probe antiquark distributions in antiproton
Unique features of D-Y: antiquarks, unstable hadrons…

5. Fermilab Dimuon Spectrometer5

7. J-PARC 50 GeV 7

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

9. R. Z. Yang, JCP, Perdekamp, PL B680 (2009) 231

10. 300 pb-1 integrated luminosity
R. Z. Yang, JCP, Perdekamp, PL B680 (2009) 231

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

12. Charge Symmetry Violation in PDF?
See recent review of Londergan, JCP, and Thomas (arXiv: )

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

14. 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)

15. Charge symmetry violating
Charge-symmetric
R. Yang and JCP, preprint

16. Charge symmetry violating
Charge-symmetric
R. Yang and JCP, preprint

17. Modification of Parton Distributions in Nuclei
EMC effect observed in DIS
(Ann. Rev. Nucl. Part. Phys., Geesaman, Sato and Thomas)
Extensive studies by Kumano et al. and Strikman et al.
F2 contains contributions from quarks and antiquarks
How are the antiquark distributions modified in nuclei?

18. Drell-Yan on nuclear targets
The x-dependence of can be directly measured
PRL 83 (1999) 2304
PRL 64 (1990) 2479

19. Flavor dependence of the EMC effects ?
Gold nucleus
Q2= 10 GeV2
Isovector mean-field generated in Z≠N nuclei can modify nucleon’s u and d PDFs in nuclei
Cloet, Bentz, and Thomas, arXiv:
SIDIS (JLab proposal) and PVDIS (P.Souder)
Pion-induced Drell-Yan ? 19

20. (Dutta, JCP, Cloet, Gaskell, arXiv:1007.3916)
W+, W- production in P+A collision is also sensitive to flavor-dependent EMC

21. Related to quark’s transverse momentum and/or transverse spin
Probing novel PDFs with the Drell-Yan
Related to quark’s transverse momentum and/or transverse spin
1) Transversity
2) Sivers function
3) Boer-Mulders function 21

22. Transversity and Transverse Momentum Dependent PDFs are probed in Semi-Inclusive DIS
Unpolarized
Boer-Mulders
Transversity
Polarized target
Sivers
Polarzied beam and target
SL and ST: Target Polarizations; λe: Beam Polarization 22

23. Transversity and Transverse Momentum Dependent PDFs are also probed in Drell-Yan23

24. Transverse Momentum Dependent PDFs with polarized Drell-Yan24

25. Boer-Mulders function h1┴ from Drell-Yan
● Observation of large cos(2Φ) dependence in Drell-Yan with pion beam ●
● How about Drell-Yan with proton beam?
194 GeV/c π + W
Boer, PRD 60 (1999) 25

26. Azimuthal cos2Φ Distribution in p+p and p+d Drell-Yan
E866 Collab., Lingyan Zhu et al., PRL 99 (2007) ; PRL 102 (2009)
Smallνis observed for p+d D-Y
Boer-Mulders function h1┴:
ν(π-Wµ+µ-X)~ [valence h1┴(π)] * [valence h1┴(p)]
ν(pdµ+µ-X)~ [valence h1┴(p)] * [sea h1┴(p)]
Sea-quark BM functions are much smaller than valence quarks 26

27. Results on cos2Φ Distribution in p+p Drell-Yan
L. Zhu, J.C. Peng, et al., PRL 102 (2009)
p+p
QCD (Boer, Vogelsang; Berger, Qiu, Rodriguez-Pedraza)
p+d
Combined analysis of SIDIS and D-Y by Melis et al.
More data are anticipated from Fermilab E906

28. Transversity and Transverse Momentum Dependent PDFs are also probed in Drell-Yan28

32. PAC recommends preparation of full proposal
From Y. Goto
PAC recommends preparation of full proposal

33. Future prospect for Drell-Yan experiments
Fermilab p+p, p+d, p+A
Unpolarized beam and target
RHIC
Doubly and singly polarized p+p collision
COMPASS
π-p and π-d with polarized targets
FAIR
Polarized antiproton-proton collision
J-PARC
Possibly polarized proton beam and target
JINR
NICA with polarized target
IHEP
SPASCHARM with polarized target p-p and π-p

34. Outstanding questions to be addressed by future Drell-Yan experiments
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

35. Summary
The Drell-Yan process is a powerful experimental tool complementary to the DIS for exploring quark structures in nucleons and nuclei.
Unique information on flavor structures of sea-quark has been obtained with Drell-Yan experiments. First results on TMD have also been extracted.
On-going and future Drell-Yan experiments at various hadron facilities can address many important unresolved issues in the spin and flavor structures of nucleons and nuclei.