Polarized Drell-Yan Experimentat J-PARC

J-PARC Meeting for Spin and Hadron Physics

Nishina Hall at RIKEN

April 7th, 2008

Yuji Goto (RIKEN/RBRC)

April 7, 2008 2

J-PARC proposals• P04: measurement of high-mass dimuon production at the 50

-GeV proton synchrotron– spokespersons: Jen-Chieh Peng (UIUC) and Shinya Sawadas (KEK)– collaboration: Abilene Christian Univ., ANL, Duke Univ., KEK, UIUC, L

ANL, Pusan National Univ., RIKEN, Seoul National Univ., TokyoTech, Tokyo Univ. of Science, Yamagata Univ.

– including polarized physics program, but not discussed– “deferred”

• P24: polarized proton acceleration at J-PARC– contact persons: Yuji Goto (RIKEN) and Hikaru Sato (KEK)– collaboration: ANL, BNL, UIUC, KEK, Kyoto Univ., LANL, RCNP, RIK

EN, RBRC, Rikkyo Univ., TokyoTech, Tokyo Univ. of Science, Yamagata Univ.

– polarized Drell-Yan included as a physics case– “no decision”

• Next proposal for the polarized physics program– to be submitted

April 7, 2008 3

Origin of the nucleon spin 1/2 ?

• EMC experiment at CERN– total quark spin constitutes a small fraction of the nucleon

spin• integration in x = 0 ~ 1 makes uncertainty• more data to cover wider x region with more precise data necessa

ry

– SLAC/CERN/DESY/JLAB experiments

• Gluon spin contribution ?– scaling violation in polarized DIS

• success of the evolution equation of the perturbative QCD • limited sensitivity due to a limited range of Q2

– semi-inclusive polarized DIS– polarized hadron collision

• Orbital angular momentum ?

Lg 2

1

2

1

)%syst(14)stat(912

J. Ashman et al., NPB 328, 1 (1989).

“proton spin crisis”

%20~

longitudinally polarized measurements

transversely polarized measurements

dd

ddALL

April 7, 2008 4

Gluon spin contribution• ALL in neutral pion production

– mid-rapidity at RHIC, s = 200 GeV][][][ qqgqggA qqgqggLL

gg + qg dominantsensitive to the gluon reaction

G = 0.4at Q2=1(GeV/c)2

G = 0.1at Q2=1(GeV/c)2

GRSV-std scenario, G = 0.4 at Q2 = 1(GeV/c)2,excluded by data on more than 3-sigma level

April 7, 2008 5

Flavor-sorted quark polarization

• Weak boson production– RHIC spin

s = 500 GeV• 2009 –

– parity-violating asymmetry AL

– reduction of uncertainties to determine the quak spin contribution and gluon spin contribution G to the proton spin

)()()()(

)()()()(

baba

babaWL xuxdxdxu

xuxdxdxuA

April 7, 2008 6

Transverse single-spin asymmetry (SSA)

+

K

p

p

• Link to orbital angular momentum in the nucleon– forward rapidity

• Fermilab E704, s = 20 GeV• RHIC, s = 200 GeV

explained by many undetermineddistribution and fragmentationfunctions: transversity, Sivers function,Collins function

April 7, 2008 7

Drell-Yan experiment• The simplest process in hadron-hadron reactions

– no QCD final-state effect– no polarized Drell-Yan experiment done yet– flavor asymmetry of the sea-quark distributions

• unpolarized and longitudinally-polarized measurements

– orbital angular momentum in the nucleon• Sivers effect (no Collins effect)

– transversity distribution function, etc.

• Why at J-PARC ?– polarized beam feasible in discussions with J-PARC and B

NL accelerator physicists– high intensity/luminosity for small Drell-Yan cross section

DIS Drell-Yan

April 7, 2008 8

Flavor asymmetry of sea-quark distribution

• Fermilab E866

• Possible origins– meson-cloud model

• virtual meson-baryon state

– chiral quark model

– instanton model– chiral quark soliton model

)(

)(1

2

1~

2 2

2

xu

xdpp

pd

012.0118.0)]()([

011.00803.0)]()([

CTEQ5Mwith

1

0

35.0

015.0

xuxddx

xuxddx

, , npp

April 7, 2008 9

Flavor asymmetry of sea-quark distribution + is the origin of -quark

excess in the proton?d

April 7, 2008 10

Dimuon experiment at J-PARC (P04)– based on the Fermilab spectrometer for 800 GeV– length to be reduced but the aperture to be increased– two vertically bending magnets with pT kick of 2.5 GeV/c a

nd 0.5 GeV/c– tracking by three stations of MWPC and drift chambers– muon id and tracking

tapered copper beam dump and Cu/C absorbers placed within the first magnet

April 7, 2008 11

Polarized Drell-Yan experiment at J-PARC

• Longitudinally-polarized measurement– ALL measurement

– flavor asymmetry of sea-quark polarization

chiral quark solitonmodel prediction

120-day run75% polarization for a 51011 protons/spillpolarized solid NH3 target, 75% hydrogen polarization and 0.15 dilution factor

GS-CGS-AGRSV

April 7, 2008 12

Flavor asymmetry of sea-quark polarization• Polarized Drell-Yan experiment at J-PARC

– x = 0.25 – 0.5

• W production at RHIC– x = 0.05 – 0.1

GS-CGS-AGRSV

reduction of uncertainties to determine the quak spin contribution and gluon spin contribution G to the proton spin

April 7, 2008 13

Polarized Drell-Yan experiment at J-PARC• Orbital angular momentum

– in hadron-hadron reaction, no direct link between measurement and theory (yet)

– but, any partonic transverse motion and correlation should be related

• Sivers effect / higher-twist effect

• SSA (AN) measurement– Sivers effect and higher-twist effe

ct provide the same description of SSA on Drell-Yan and semi-inclusive DIS at moderate qT: QCD << qT

<< Q– Sivers function in Drell-Yan shoul

d have a sign opposite to that in DIS

• sensitive QCD test between e+p data and p+p data

4 < M+- < 5 GeVintegrated over qT

1000 fb-1 (120-day run), 75% polarization, no dilution factorTheory calculation by Ji, Qiu, Vogelsang and Yuan based on Sivers function fit of HERMES data

April 7, 2008 14

Polarized Drell-Yan experiment at J-PARC

• ATT measurement

– h1(x): transversity• remaining leading-order

distribution function of the nucleon

• SSA measurement, sin(+S) term

– h1(x): transversity

– h1(1)(x): Boer-Mulders f

unction (1st moment of)

2

2

21112

21112

cos1

)2cos(sinˆ

))21()()((

))21()()((

ˆ

21

SSTT

qqqq

qqqq

TTTT

a

xfxfe

xhxhe

aA

qqqq

qqqq

xfxfe

xhxhe

A))21()()((

))21()()((

2

1ˆ2111

2

211)1(

12

April 7, 2008 15

Unpolarized Drell-Yan experiment at J-PARC• Boer-Mulders function h1

(x, kT2)

– angular distribution of unpolarized Drell-Yan

– Lam-Tung relation reflect the spin-1/2 nature of quarks– violation of the Lam-Tung relation suggests non-perturbati

ve origin– correlation between transverse quark spin and quark tran

sverse momentum

2 21 31 cos sin 2 cos sin cos 2

4 2

d

d

21 ,

L.Y. Zhu,J.C. Peng, P. Reimer et al.hep-ex/0609005

With 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)

April 7, 2008 16

Experimental condition study• Previous simulation study which made the figure below w

as wrong– target position was fixed at z = 0 (at the edge of the first magnet)– correctly, this should be z = -1800 cm ~ -1300 cm (50 cm target)– yield should be ~5 times smaller

– but, higher beam intensity is possible for unpolarized liq.H2 target– 10 times higher possible? 51012 ppp = 11012 /sec ?

1000 fb-1 (120-day run),75% polarization, no dilution factorTheory calculation by Ji, Qiu, Vogelsang and Yuan based on Sivers function fit of HERMES data

PYTHIA simulation: mass = 4 – 5 GeV/c2

beam intensity: 51011 ppp = 11011 /sec120 day = 107 secbeam on target: 51017 (with 50% duty factor)number density of liq.H2 target: 0.429x1023 /cm3

luminosity = botnumber densitytarget length= 1000 fb-1

April 7, 2008 17

Experimental condition study• J-PARC experiment should be optimized for 4 GeV/c2 virt

ual photon– PYTHIA simulation: mass = 4 – 4.1 GeV/c2, xF = 0.2 – 0.4– each of magnet/detector geometry same as E906, but total appa

ratus length 60% shorter

April 7, 2008 18

Experimental condition study

• E906 optimized for 7 GeV/c2 virtual photon– PYTHIA simulation

mass = 7 – 7.1 GeV/c2, xF = 0.2 – 0.4 mass = 4 – 4.1 GeV/c2, xF = 0.2 – 0.4

April 7, 2008 19

Experimental condition study

• Smaller boost– wider aperture of the first magnet necessary

• Sivers effect measurement– single beam-spin asymmetry– maybe easier to use nuclear targets

• More studies– absorber & beam target thickness, etc.– trigger rate and resolution

April 7, 2008 20

pQCD studies by Yokoya-san, et al.

• NLO/NNLO

April 7, 2008 21

pQCD studies by Yokoya-san, et al.

• Scheme dependence

April 7, 2008 22

pQCD studies by Yokoya-san, et al.

April 7, 2008 23

pQCD studies by Yokoya-san, et al.

April 7, 2008 24

pQCD studies by Yokoya-san, et al.

April 7, 2008 25

pQCD studies by Yokoya-san, et al.

April 7, 2008 26

pQCD studies by Yokoya-san, et al.

April 7, 2008 27

pQCD studies by Yokoya-san, et al.

April 7, 2008 28

pQCD studies by Yokoya-san, et al. s = 62 GeV

April 7, 2008 29

pQCD studies by Yokoya-san, et al. s = 10 GeV

April 7, 2008 30

pQCD studies by Yokoya-san, et al.

April 7, 2008 31

pQCD studies by Kawamura-san, et al.

April 7, 2008 32

pQCD studies by Kawamura-san, et al.

April 7, 2008 33

Summary• Polarized Drell-Yan experiment with dimuon measurment

using polarized proton beam at J-PARC has a rich physics programs– flavor asymmetry of sea-quark polarization higher precision fo

r and G– SSA measurements for Sivers and higher-twist effects and trans

versity link to orbital-angular momentum

• We propose to make the J-PARC facility allow acceleration of polarized proton beams to 30-50 GeV– feasible in discussion with J-PARC and BNL accelerator physicis

ts– technically, there is no showstopper

• Theoretical studies at J-PARC energy has progressed– showing convergence to compare with experimental data

• More studies for experimental condition to be done– for the next proposal