Drell-Yan Experiments for determining Nucleon Partonic Structures

Wen-Chen Chang Institute of Physics, Academia Sinica, Taiwan

The International Symposium on Physics of Unstable Nuclei 2014

ISPUN14Ho Chi Minh City, Vietnam, November 3-8, 2014

How to Probe the Structure of Nucleus / Nucleon?

2

probeddp

Shoot high-energy beam

Elastic Electron Scattering of Nuclei and Nucleons

3

Nuclear Form Factor Nucleon Form Factor

2 2max 0.16 GeVQ

Charge distributions of nuclei and protons.

2 2max 1.0 GeVQ

From Elastic Scattering to Deeply Inelastic Scattering (DIS)

4

Elastic scatteringInelastic scattering

resonance

• Very weak Q2-dependence, form factor1!

• Scattering off point-like objects?

2 2max 10.0 GeVQ

Quark-Parton Model (Feynman)

5

pquark = xPproton

0')( 222 quarkquark mpqxP

M

Q

Pq

QxqqxP

22 02

222

0 < x < 1Limiting case: x = 1,

elastic scattering

Bjorken-x: momentum fraction of struck parton

12 2 2 22 xp p pW M M Q M

6

“Elastic” Way

“Inelastic” Way

7

“Deeply Inelastic” Way

8

Structure Known

9

The Drell-Yan Process: Massive Di-lepton pairs from Hadron-Hadron Collisions

10

2

1 2

Qx x

s

p+U +X

PRL 25 (1970) 1523S.D. Drell and T.M. Yan, PRL 25 (1970) 316

Dimuon Invariant Mass Spectrum

11

Indium-Indium collisions at 158 GeV/nucleonNA60, PRL 99 (2007) 132302

Drell-Yan

p+U +X

PRL 25 (1970) 1523

J/

J/

Drell-Yan

Complementarity between DIS and Drell-Yan

12

Parton Distribution Functions (PDF) of Protons

13

Valance quarksSea quarks

x: momentum fraction of partons

14

Is in the Proton?

Gottfried Sum Rule

1

0

1 1

0 0

22[( ( ) ( )) / ]

1 2( ( ) ( )) ( ( )

( f ( )

( ))3 31

(3

))

G

v

n

v

pS x x x dx

u x d x dx u x d x dx

FF

i u x d x

=

22 , : Structure functions of proton and neutron from DISnp FF

15

Experimental Measurement of Gottfried Sum

New Muon Collaboration (NMC), Phys. Rev. D50 (1994) R1

SG = 0.235 ± 0.026

( Significantly lower than 1/3 ! )

S. Kumano, Physics Reports, 303 (1998) 183

1

3

16

Naïve Assumption:NMC (Gottfried Sum

Rule):

NA51 (Drell-Yan, 1994):

Light Antiquark Flavor Asymmetry: Drell-Yan Experiments

NA 51 Drell-Yan confirms

17

Naïve Assumption:NMC (Gottfried Sum

Rule):

NA51 (Drell-Yan, 1994):

E866/NuSea (Drell-Yan, 1998):

Light Antiquark Flavor Asymmetry: Drell-Yan Experiments

Origin of ?Pauli blocking of

valance quarks (Field and Feynman 1977)

Meson cloud in the nucleons (Thomas 1983, Kumano 1991): Sullivan process in DIS.

Chiral quark model (Eichten et al. 1992; Wakamatsu 1992): Goldstone bosons couple to valence quarks.

18

“Flavor Structure of the Nucleon Sea”W.-C. Chang and J.-C. Peng, arXiv:1406.1260Prog. in Part. and Nucl. Phys. 79 (2014) 95.

by FNAL E906/SeaQuest

19

Fixed Target

Beam lines

Tevatron 800 GeVMain

Injector 120 GeV

( ( ) / ( )) up to 0.45d x u x x

Fermilab E906 Physics data taking:

Feb, 2014 – Dec, 2015. 1H, 2H, and nuclear targets Unpolarized Drell-Yan using

120 GeV proton beam

KEK, RIKEN, Tokyo Tech, Yamagata, AS and U.S. institutes

x+x x-x

t

GPDs

P P’

Generalized Parton Distribution (GPD)

20

( ,0,0) ( ) ( )

( ,0,0) ( ) ( )

f f f

f f f

H x q x q x

H x q x q x

1

1

1

1

2

1

1

1

1

1

( , , ) ( )

( , , ) ( )

( , , ) ( )

( , , ) ( )

ff

ff

f Af

f pf

dx H x t F t

dx E x t F t

dx H x t g t

dx E x t g t

)]0,,()0,,([2

1

2

1 1

1

xExHxdxLJ ffff

f

),,( txGPD

2)'( PPt

0t

5

( , , ) ( , , )

( , , ) ( , , )

f f

f f

no spin flip H x t H x t

spin flip E x t E x t

0t

Accessing GPD using Lepton Beam

21

Deeply Virtual Compton Scattering

2 0q 2 0q

Deeply Virtual Meson Production

JLAB, HERMES@DESY, COMPASS@CERN

Explored Regions of Generalized Parton Distribution (GPD)

22

Spacelike vs. Timelike ProcessesMuller et al., PRD 86 (2012) 031502

23

Deeply Virtual Meson Production Exclusive Meson-induced Drell-Yan

2 0q 2 0q

channel crossings u

• Cross sections of exclusive DY process drop with an increase of beam energy. No sensitivity to parton d.o.f. if beam energy is small.

• The beam energy of pions at J-PARC at 10-20 GeV might be most ideal for studying this hard exclusive process.

24

High-res., High-momentum Beam Line at J-PARC• High-intensity secondary Pion beam

• High-resolution beam: Dp/p~0.1%

Dispersive Focal Point (DFP)Dp/p~0.1%

Collimator

15kW Loss Target(SM)

Exp. Target (FF)

Pion BeamUp to 20 GeV/c

H. Noumi

See K. Tanaka’s talk

25

High-res., High-momentum Beam Line• High-intensity secondary Pion beam

– >1.0 x 107 pions/sec @ 20GeV/c• High-resolution beam: Dp/p~0.1%

* Sanford-Wang:15 kW Loss on Pt, Acceptance :1.5 msr%, 133.2 m

Open a new platform for hadron physics

0 5 10 15 201.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

[GeV/c]

Co

un

ts/s

ec

0 5 10 15 201.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

[GeV/c]

Co

un

ts/s

ec

Prod. Angle = 0 deg. (Neg.)

p-

K-

pbar

p+

K+

Prod. Angle = 3.1 deg (Pos.)

H. Noumi

26

J-PARC E50 Spectrometer + MuID

p-

LH2-target

Ring ImageCherenkovCounter

Internal DC

FM magnet

ps-

K+

Fiber tracker

Beam GC

Internal TOF

Internal TOFDC

TOF wall

2m

Decay p(p+)

20 GeV/cBeam p-

Acceptance: ~ 60% for D*, ~80% for decay p+ Resolution: Dp/p~0.2% at ~5 GeV/c　（ Rigidity ： ~2.1 Tm)

||<60

Scintillator Muon trigger device

20-GeV N+-N MX In E-50 Spectrometer + MuID

27

Red: Exclusive DY ( 5 pb )Blue: Inclusive DY ( 500 pb )Green: random BG from meson decay

After 200-day data-taking

Assumption: Δp/p = 0.2 %

Missing Mass MX (GeV2)

Nev

ent The signal of exclusive

Drell-Yan processes can be clearly identified in the missing mass spectrum of dimuon pairs.

S. Sawada (KEK)S. Kumano (KEK)J.C. Peng (UIUC)T. Sawada (AS)W.C. Chang (AS)

Explored Regions of Generalized Parton Distribution (GPD)

28

J-PARC (exclusive DY)

SummaryDrell-Yan process, based on the EM

annihilation of quarks and antiquarks from two hadrons, is a powerful experimental tool for exploring nucleon quark structures.

Unique information of the x-dependence of sea quark flavor asymmetry has been obtained with Drell-Yan experiments.

SeaQuest/E906 experiment at Fermilab will obtain at large-x regions.

The study of exclusive meson-induced Drell-Yan process at J-PARC will provide a valuable and complementary way of measuring the GPD structures of nucleons. 29

Backup

30

Momentum Dependence of the Flavor Structure of the Nucleon Sea: NMC vs E866J.C. Peng et al., PLB 736 (2014) 411

31

JR14 NMC

32

Nucleon Partonic StructureWigner Distribution

Transverse Momentum Dependent PDF

Generalized Parton Distr.

d 2kt dzF.T.

d2k t

PDF

dx

Form Factors

GPD

Ji, PRL91,062001(2003)

( , , )TW r x k

f( , )Tx k

f( )x

H( , , t)x

1 2( ), ( )F t F t

d3 r