1

Large-X PDFs in the Drell-Yan Process

Jen-Chieh Peng

“3rd International Workshop on Nucleon Structure at Large Bjorken X”

Jefferson Lab, Newport News, Oct. 13-15, 2010

University of Illinois at Urbana-Champaign

2

• 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

Outline

33

Complimentality between DIS and Drell-Yan

Both DIS and Drell-Yan process are tools to probe the quark and antiquark structure in hadrons (factorization, universality)

DIS Drell-Yan

McGaughey, Moss, JCP,

Ann.Rev.Nucl. Part. Sci. 49 (1999) 217

4

Lepton-pair production provides unique information on parton distributions

194 GeV/c

W X

800 GeV/c

p W X

1.8 TeV

p p l l X

Probe antiquark distribution in nucleon Probe antiquark

distribution in pion Probe antiquark

distributions in antiproton

Unique features of D-Y: antiquarks, unstable hadrons…

55

Fermilab Dimuon Spectrometer(E605 / 772 / 789 / 866 / 906)

"Nuclear Dependence of Drell-Yan and Quark

1) Fermilab E772

2) Fermilab E789

(proposed in 1986 and completed in 1988)

(proposed in 1989 and completed in 199

onium Production"

"Search for Two-Bo

1)

dy Decays of Heavy Quark Mesons"

"Determination of / Ratio of the Proton via Drell-Ya

(proposed in 1993 and completed in 13) Fermilab E866

4) Fermilab E906

996)

(proposed in 1999, will run in 2010-20

n

)

"

13

d u

"Drell-Yan with the FNAL Main Inje ctor"

6

/ flavor asymmetry from Drell-Yand u

2 2

1/ 2 (1 ( ) / ( )Dr )

2ell-Yan: pd pp d x u x

2 2

21 2 1 2

1 2 1 2. .

4( ) ( ) ( ) ( )

9 a a a a aaD Y

de q x q x q x q x

dx dx sx x

1 2 :at x x

800 GeV proton beam

on hydrogen and deuterium

mass spectrum

77

What's next for / ?d u2

21 2 1 2

1 2 1 2

4[ ( ) ( ) ( ) ( )

1]

3DY

i ii

de q x q

sx q x q x

dx dx x x

J-PARC 50 GeV

Intriguing / behavior at large

can be studied at lower beam energies

d u x DY cross section is 6 times larger

at 120 GeV than at 800 GeV

120 GeV proton bea

Fermilab E-906

(P. Reimer, D. Geesaman et al.)

J-PARC P-04

(J. Peng, S. Sawada et

m

50 GeV proton

al

be

.)

am

8

/ from W production d u production in collisionW p p

p p W x p p W x

( )u d W ( )d u W

No nuclear effects !

No assumption of charge-symmetry !

Large Q2 scale !

21

21

( )( )

(

( )(

( ) ))

( )

FF

F

dpp W X

dx u xR x

d d xpp

d x

uW xXdx

9

u d

u d

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

/ from W production at RHICd u/ ( )

( ) at 500 GeV/ ( )

FF

F

d dx pp W xR x s

d dx pp W x

u d

u d

10

/ from W production at PHENIXd u/ ( )

( ) at 500 GeV/ ( )

d dy pp W x l xR y s

d dy pp W x l x

detection

u d

300 pb-1 integrated luminosity

detectione

u d

u d detection

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

11

Gluon distributions in proton versus neutron?

New data on ( / ) / 2 ( / ) expected for E906p d J p p J

/ 2 [1 ( ) / ( )] / 2:

/ , : / 2 [1 ( ) / ( )] / 2

pd pp

pd ppn p

d x uDrell Y x

g

an

J x g x

Lingyan Zhu et al., PRL, 100 (2008) 062301 (arXiv: 0710.2344)

Gluon distributions in proton and neutron are very similar

E866data: ( ) / 2 ( )p d X p p X

12

Charge Symmetry Violation in PDF?

2 2

Charge symmetry : rotation around isospin axis by 180

Charge symmetry in PDF is generally assumed, bu

( ; .)

A compari

t not tested

son of with shows upper limit o f

n

y

p n pp n u d u d u d u d etc

F F

I

The NuTeV anomaly in the Weinberg angle could be partly

explained b

(Lon

y ch

CS breaking

of 5 1

arge symmetry vio

dergan and

latio

Thomas, hep-ph/0407247)

(Londergan and Thomas,

n

0%

P

L B558

(2003) 132)

See recent review of Londergan, JCP, and Thomas (arXiv:0907.2352)

13

Charge Symmetry violation from MRST Global fits

(Eur. Phys. J. C35, 325 (2004))

4 0.5(

(

) (1 ) ( 0.0

) ( ) ( )

Best fit: 0.2

0.8 0.65 (90%

( ) ( ) ( )

( )

C.L.)

90

(

9

)

)

( )

V V

p nV V V

p nV V V

u x d x f x

d x d x u x

u x u

f x x x

x

x

x d

Best fit: 0.08

(8% of C

0.08 0.18 (90

( ) ( )[

SV

1 ]

( ) ( )[

fo

% C

1 ]

r

.L

.

!

)

sea )

n p

n p

u x d x

d x u x

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

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

15

CSV from W production2 / ( )

( ) at 500 GeV/ ( )

FF

F

d dx pp W xR x s

d dx pd W x

2 2

2 2

/ ( )( )

2 / ( )

( ) ( )11

2 (

for 0, ( ) is sensitive to

valence-quar

) ( )

k CSV

FF

F F

F

d dx pd W xR x

d dx pp W x

d x d x

u x u x

x R x

R. Yang and JCP, preprint

Charge symmetry violating

Charge-symmetric

16

CSV from W production2 / ( )

( ) at 500 GeV/ ( )

FF

F

d dx pp W xR x s

d dx pd W x

2 2

2 2

/ ( )( )

2 / ( )

( ) ( )11

2 ( ) ( )

for 0, ( ) is sensitive to

sea-quark CSVF F

FF

F

d dx pd W xR x

d dx pp W x

d x d x

u x

x

u x

R x

R. Yang and JCP, preprint

Charge-symmetric

Charge symmetry violating

17

Modification of Parton Distributions in NucleiEMC effect observed in DIS

How are the antiquark distributions modified in nuclei?F2 contains contributions from quarks and antiquarks

(Ann. Rev. Nucl. Part. Phys., Geesaman, Sato and Thomas)

Extensive studies by Kumano et al. and Strikman et al.

18

Drell-Yan on nuclear targets

The x-dependence of can be directly measured( ) / ( )A Nu x u x

( )

( )

pAA

pdN

u x

u x

PRL 64 (1990) 2479 PRL 83 (1999) 2304

No evidence for enhancement of antiquark in niclei !?E906 will extend the measurement to larger x

1919

Cloet, Bentz, and Thomas, arXiv:0901.3559

Isovector mean-field generated in Z≠N nuclei can modify nucleon’s u and d PDFs in nuclei

How can one check this prediction?

Flavor dependence of the EMC effects ?

• SIDIS (JLab proposal) and PVDIS (P.Souder)

• Pion-induced Drell-Yan ?

Q2= 10 GeV2

Gold nucleus

20

(Dutta, JCP, Cloet, Gaskell, arXiv:1007.3916)

W+, W- production in P+A collision is also sensitive to flavor-dependent EMC

2121

Related to quark’s transverse momentum and/or transverse spin

1) Transversity

2) Sivers function

3) Boer-Mulders function

Correlation between and q Ns S

Correlation between and q qs k

Correlation between and N qS k

Three transverse quantities:

1) Nucleon transverse spin

2) Quark transverse spin

3) Quark transverse

mo

Three diff

me

er

ntum

ent correlations

N

q

q

S

s

k

Probing novel PDFs with the Drell-Yan

2222

4

26 4

Q

sxd

),()(])1(1{[ 211

,

22 h

qq

qqq PzDxfey

22 (1) 2

1 12,

22 (1) 2

1 12,

2 21 1

,

cos(2 )

sin(2 )

(1 ) ( ) ( , )4

| |

s

(1 ) ( ) ( , )4

| | (1 ) ( ) (in( )) ,

q qhq h

q qN h

q qhL q L h

q qN h

q

lh

lh

l lh

qhST q h

q qh

Py e h x H z P

z M M

PS y e h x H z P

z M M

PS y e h x H z P

zM

2 2 (1) 21 1

,

32 (2) 2

1 13 2,

2 21 1

,

1| | (1 ) ( ) ( , )

2

| | (1 ) ( ) ( , )6

1| | (1 ) ( ) ( , )

2

1| | (1 )

sin( )

sin(3 )

co ( )2

s

q qhT q T h

q qN

q qhT q T h

q qN h

q qe L q h

q q

he T

N

l lh S

l lh S

l lh S

PS y y e f x D z P

zM

PS y e h x H z P

z M M

S y y e g x D z P

PS y y e

zM

2 (1) 2

1 1,

( ) ( , )}q qq T h

q q

g x D z P

Unpolarized

Polarized target

Polarzied beam and

target

SL and ST: Target Polarizations; λe: Beam Polarization

Sivers

Transversity

Boer-Mulders

Transversity and Transverse Momentum Dependent PDFs are probed in Semi-Inclusive DIS

2323

Transversity and Transverse Momentum Dependent PDFs are also probed in Drell-Yan

1 1

1

a) Boer-Mulders functions:

b) Sivers functions

- Unpolarized Drell-Yan:

- Single transverse spin asymmetry in polarized Drell-Yan:

:

c) Transv

( ) ( ) cos(2 )

( ) ( )

e

DY q q

DYN T q q q

d h x h x

A f x f x

1 1

rsity distributions:

Drell-Yan does not require knowledge of the fragmentation functions

T-odd TMDs are pre

- Double transverse spin asymmetry in polarized Drell-Yan:

(

d

) ( )DYTT q qA h x h x

icted to change sign from DIS to DY

(Boer-Mulders and S

Remains to be te

ivers functions)

sted experimenta lly!

2424

Transverse Momentum Dependent PDFs with polarized Drell-Yan

Ralston and Soper

Pire and Ralston

Tangerman and Mulders

Boe

(NP B152 (1979) 109)

(PR D28 (1983) 260)

(PR D51 (1995) 3357)

(r

Arnold, Metz, and

PR D60 (1999) 0

Schlegel

14012)

(PR D79 ( 2009)

034005)

2525

Boer-Mulders function h1┴ from Drell-Yan

1

1

is a time-reversal odd, chiral-odd TMD parton distribution

can lead to an azimuthal cos(2 ) dependence in Drell-Yan

h

h

Boer, PRD 60 (1999) 014012

● Observation of large cos(2Φ) dependence in Drell-Yan with pion beam

●

● How about Drell-Yan with proton beam?

194 GeV/c π + W

2 21 31 cos sin 2 cos sin cos 2

4 2

d

d

1 1 ( ) ( )q qh x h x

2626

Boer-Mulders function h1┴:

ν(π-Wµ+µ-X)~ [valence h1┴(π)] * [valence

h1┴(p)]

ν(pdµ+µ-X)~ [valence h1┴(p)] * [sea h1

┴(p)]

Azimuthal cos2Φ Distribution in p+p and p+d Drell-Yan

E866 Collab., Lingyan Zhu et al., PRL 99 (2007) 082301; PRL 102 (2009)

182001

Sea-quark BM functions are much smaller than valence quarks

Smallνis observed for p+d D-Y

27

Results on cos2Φ Distribution in p+p Drell-Yan

QCD (Boer, Vogelsang; Berger, Qiu, Rodriguez-Pedraza)

p+p

p+d

L. Zhu, J.C. Peng, et al., PRL 102 (2009) 182001

More data are anticipated from Fermilab E906

Combined analysis of SIDIS and D-Y by Melis et al.

2828

Transversity and Transverse Momentum Dependent PDFs are also probed in Drell-Yan

1 1

1

a) Boer-Mulders functions:

b) Sivers functions

- Unpolarized Drell-Yan:

- Single transverse spin asymmetry in polarized Drell-Yan:

:

c) Transv

( ) ( ) cos(2 )

( ) ( )

e

DY q q

DYN T q q q

d h x h x

A f x f x

1 1

rsity distributions:

Drell-Yan does not require knowledge of the fragmentation functions

T-odd TMDs are pre

- Double transverse spin asymmetry in polarized Drell-Yan:

(

d

) ( )DYTT q qA h x h x

1 1

icted to change sign from DIS to DY

(Boer-Mulders and Sivers functi

Remain

( )ons)

s to be tested experimentally!

( )T q DY T q DISf x f x

29

30

31

32PAC recommends preparation of full proposal

From Y. Goto

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

• 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 to be addressed by future Drell-Yan experiments

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.