Spin Physics Results from RHICSpin Physics Results from RHICInternational conference on QCD and Hadron PhysicsInternational conference on QCD and Hadron Physics

June 16-20, 2005, BeijingJune 16-20, 2005, Beijing

Naohito SAITONaohito SAITO(Kyoto University)(Kyoto University)

OutlineOutline

• Spin Structure of the NucleonSpin Structure of the Nucleon

• Status of RHIC Spin ProjectStatus of RHIC Spin Project

• Results and Future ProspectsResults and Future Prospects– Gluon PolarizationGluon Polarization– Single Transverse-Spin AsymmetriesSingle Transverse-Spin Asymmetries– Sea-quark Polarization Sea-quark Polarization

• SummarySummary

Proton Spin Crisis?Proton Spin Crisis?• Proton has gone through many crisisProton has gone through many crisis

– Mass : Mass : mmuu~5 ~5 MeV/MeV/cc22, , mmdd~10 ~10 MeV/MeV/cc22

• Saved by constituent quark modelSaved by constituent quark model– Momentum : Momentum :

• Saved by gluon momentumSaved by gluon momentum

• Spin Spin – Helicity SR: Helicity SR:

– Theory guideline for separation (nf=3)Theory guideline for separation (nf=3) (Ji, Tang, and Hoodboy)

gq

proton

LLg 2

1

2

1

5.0)( q

dxxxq

3.01.0 3.01.0)( q

dxxq

18.0163

3

2

1

2

1

f

fq n

nL 32.0

163

16

2

1

fg n

Lg

Spin Physics ExperimentsSpin Physics Experiments• COMPASSCOMPASS

– Pol.Pol.• HERMESHERMES

– Pol.ePol.e±±

• JLab Exp’sJLab Exp’s– Pol.e-Pol.e-

• RHIC SpinRHIC Spin– Pol. ppPol. pp

• BELLEBELLE– ee++ee--

Pol. Beam:

RICH-1

Pol.Target

SM1

SM2

2-stage spectrometer• LAS (Large angle) K• SAS(Small angle)

SAS

LAS

Ecal1 & Hcal1

filter 1

filter 2Ecal2 & Hcal2

RICH-2

Probing the Proton StructureProbing the Proton Structure• EM interactionEM interaction

– PhotonPhoton•Sensitive to electric chargeSensitive to electric charge22

• Insensitive to color chargeInsensitive to color charge

• Strong interactionStrong interaction– GluonGluon

•Sensitive to color chargeSensitive to color charge• Insensitive to flavorInsensitive to flavor

• Weak interactionWeak interaction– Weak BosonWeak Boson

•Sensitive to weak charge ~ flavorSensitive to weak charge ~ flavor• Insensitive to colorInsensitive to color

Parton Distribution FunctionsParton Distribution Functions• Quark DistributionsQuark Distributions

q(x,Q2)=

q(x,Q2)=

q(x,Q2)=

=

unpolarized distributionunpolarized distribution

helicity distributionhelicity distribution

transversity distributiontransversity distribution

g(x,Q2)=

g(x,Q2)=

No Transverse Gluon Distribution in 1/2

• Gluon DistributionsGluon Distributions

DIS of Lepton from NucleonDIS of Lepton from Nucleon• Structure Probed by PhotonStructure Probed by Photon

– Function of Function of xx and and QQ22=-=-qq22

– ∝∝Charge SquaredCharge Squared• Not distinguish Down and Not distinguish Down and

StrangeStrange• Insensitive to Gluon at LOInsensitive to Gluon at LO

• Objective isObjective is

• Observables areObservables are

kk’

q

p

p’

PxP=

Elastic

),(9

1),(

9

4),(

9

1

2

1),(

),(9

1),(

9

1),(

9

4

2

1),(

22221

22221

QxSQxDQxUQxg

QxSQxDQxUQxg

n

p

SDU

Proton

Neutron

Precision Data from DISPrecision Data from DIS• Precision Data in WPrecision Data in W

ide Kinematical Raide Kinematical Rangenge– QQ22 evolution agrees evolution agrees

with pQCDwith pQCD

• NotesNotes ：：– Only Fixed Target SOnly Fixed Target S

pin Experiments in pin Experiments in DIS so far…DIS so far…

– Need a Collider to Need a Collider to extend kinematical extend kinematical coveragecoverage

Q2 (GeV2)

g1

From From gg11((xx,,QQ22)) to to

Proton

Deuteron = Proton + Neutron

3He=Neutron

Proton

Deuteron = Proton + Neutron

3He=Neutron

053.09

1

9

4

9

1

2

1 0.119

9

1

9

1

9

4

2

111

SDUSDU np

p1

n1

p1

n1

053.09

1

9

4

9

1

2

1

0.119 9

1

9

1

9

4

2

1

1

1

SDU

SDU

n

p

|017.0340.0|)/(

05.025.03/3/)2()/(

015.0718.03/3/)2()/(

0029.02695.1)/(

DFSDgg

DFSDUgg

DFSDUgg

DFDUgg

nVA

VA

pVA

npVA

0083.01952.02 0112.02692.1 SDUDU

• Integrate over x (0,1)Integrate over x (0,1) ！！

• Utilize Octet Baryon Utilize Octet Baryon -Decay Constants-Decay Constants ！！

– SU(2) OKSU(2) OK ！！　　（　　（ Bjorken SRBjorken SR ））

138.0213.0

)124.0,465.0,802.0(

),,(

SDU

Constant in front of D/3

ene

ee

epe

epen

Polarised Parton DistributionsPolarised Parton Distributions• Global QCD Analysis to Extract Polarized QuaGlobal QCD Analysis to Extract Polarized Qua

rk and Gluon Distributions rk and Gluon Distributions – ((a laa la MRST, CTEQ) MRST, CTEQ)

• Four Independent Distributions are often extrFour Independent Distributions are often extracted – e.g. acted – e.g. UU((xx,,QQ22)),,DD( ),( ),S S ( ),( ), g g ( )( )– In unpolarised case, even more In unpolarised case, even more

• We have ONLY TWO independent measuremWe have ONLY TWO independent measurements ents gg11

pp((xx, , QQ22) and ) and gg11nn((xx,,QQ22))

– QQ22 evolution helps? evolution helps?

gtbcssdduu ,,,,,,,,,

Separation of Pol’ Quark Dist’sSeparation of Pol’ Quark Dist’s• Only two independent measurements Only two independent measurements gg11

pp

((xx, , QQ22) and ) and gg11nn((xx,,QQ22))

• Separation into 3 quark dist’s relies on Separation into 3 quark dist’s relies on – 11stst moments (employ moments (employ -decay const’s), -decay const’s), unless diunless di

rect measurement of sea-quarkrect measurement of sea-quark– Different coupling with Different coupling with gg((xx)) thru thru QQ22 evolution evolution

SDU

DU

SDU

a

a

28

3),()(

2

)(

)(ln

),( 2,

2

2

2

QxqxPQ

Q

QxqNSNSq

SNS

),(

),()()(

)()(

2

)(

),(

),(

)(ln 2

22

2

2

2 Qxg

QxxPxP

xPxPQ

Qxg

Qx

Q gggq

qgqqS

Non-Singlet Quark Distribution

Singlet Quark Distribution

How much do we know about g(x)?

Polarised PDFPolarised PDFAAsymmetrysymmetry A Analysis nalysis CCollaboration ollaboration

M. Hirai, S. Kumano and N. Saito, PRD (2004)M. Hirai, S. Kumano and N. Saito, PRD (2004)

• Valence Dist’s Valence Dist’s are determined are determined wellwell

• Sea Dist’ is poSea Dist’ is poorly constraineorly constrainedd

• Gluon can be eGluon can be either >0, =0, <ither >0, =0, <00

Assumptions in “ Assumptions in “ gg11 to to ””• Extrapolation to Small-Extrapolation to Small-

xx– No (solid) guideline froNo (solid) guideline fro

m Therym Thery– Regge? BFKL? Regge? BFKL? -fn at x-fn at x

=0?=0?• Flavor SU(3) assumptiFlavor SU(3) assumpti

onon– What precision?What precision?– Require independent deRequire independent de

termination of…termination of…

SAAC Collaboration in PRD (2000)

1

min)(

xdxx

RHIC Spin Physics ProgramRHIC Spin Physics Program• Accelerate and Collide Polarized Proton BeaAccelerate and Collide Polarized Proton Bea

ms with Hi-Polarization and Luminosityms with Hi-Polarization and Luminosity

• Brief HistoryBrief History– 1990: Polarized Collider WS in Penn-State U1990: Polarized Collider WS in Penn-State U– 1991: RHIC Spin Collaboration Formed1991: RHIC Spin Collaboration Formed– 1993: PHENIX and STAR integrated Spin Progra1993: PHENIX and STAR integrated Spin Progra

mm– 1995: RIKEN-BNL Collaboration (~$20M) 1995: RIKEN-BNL Collaboration (~$20M) – 2002: First Polarized Proton Collision!2002: First Polarized Proton Collision!– Long collaboration with Peking U and CIAE Long collaboration with Peking U and CIAE

1232max scm102,GeV500,200%,70 LsPB

What Do We Measure at What Do We Measure at RHIC?RHIC?• We measure spin asymmetries for cross sectionsWe measure spin asymmetries for cross sections• AALLLL: double helicity asymmetry: double helicity asymmetry

– Useful in extracting Useful in extracting gg((xx)), , qq((xx)) etc. etc.

)()(

)()(

LLA

ATT: Transversity AN:Twist-3 etc AL:Parity Violation

And various Spin Transfer Asymmetries: DNN, DLL, etc

RHIC:The First Polarised pp ColliderRHIC:The First Polarised pp Collider

STARSTAR

jetp

RHIC Spin EvolutionRHIC Spin Evolution

BRAHMS & PP2PP

STAR

AGS

LINACBOOSTER

Pol. Proton Source500 A, 300 s

Partial Siberian Snake

Siberian SnakesSpin Rotators

200 MeV PolarimeterAGS Internal Polarimeter

Rf Dipoles

0.5 1011 Pol. Protons / Bunch

PHOBOS

RHICPHENIX

RHIC pC CNI PolarimeterLocal Polarimeter

Local Polarimeter

1.0 x1011

AGS pC CNI Polarimeter

Absolute Polarimeter (Pol-Jet Tgt)

AGS Warm Snake

AGS Cold Snake

2.5 weeks

RHIC Spin: RHIC Spin: LL and and PP Progress Progress• Run 2: Run 2: AANN

– ~7nb~7nb-1-1/day/day– PPBB~20% ~20%

• Run-3:Run-3:AALLLL– 10nb10nb-1-1/day/day– PPBB~26%~26%– (AGS) 40%(AGS) 40%

• Run-4:Run-4:AALLLL– Only Machine Only Machine

StudiesStudies– 30nb30nb-1-1/day/day– PPBB~40%~40%– (AGS) 50%(AGS) 50%

• Run-5 :Run-5 :AALLLL– 55 nb55 nb-1-1/day/day– PPBB~50%~50%

>4 weeks

>4 weeks

4 days

4 days

2.93 pb-1 as of June 14, 2005

3.97 pb-1 expectedJune 25, 2005

10 weeks

10 weeks

164 nb-1 as of June 14, 2005

225 nb-1 expected June 25, 2005

温故知新温故知新• 温故知新 温故知新

– 温：　温：　 (v) heat up, re-visit (v) heat up, re-visit – 故： 故： (n) past (n) past – 知：　知：　 (v) learn, know (v) learn, know – 新：　新：　 (n) new (n) new

revisit the past to learn something newrevisit the past to learn something new

• RHIC is RHIC is 温膠知新温膠知新– 膠：　膠：　 (n) glue (n) glue gluon gluon 　（膠子） 　（膠子） – Revisit/Heat-up Gluon to Learn Something Revisit/Heat-up Gluon to Learn Something

New!New!

Gluon PolarizationGluon Polarization

Gluon Polarization in the Gluon Polarization in the ProtonProton• Hunting for Hunting for gg

– Direct ProbeDirect Probe• FNAL E704 FNAL E704

– High-pT High-pT 00

– High-mass Multi-High-mass Multi-pairpair• DESY HERMESDESY HERMES

– High-pT hadron pairHigh-pT hadron pair– Indirect ProbeIndirect Probe

• NLO Analysis by SMCNLO Analysis by SMC

PLB261(1991)197

PLB336(1994)269

PRD58(1998)112002

PRL 84(00)2584GeV4.19s

GeV4.19s

Status ofStatus ofg/gg/g((xx) ) from Lepton Scat.from Lepton Scat.• Gluon Gluon

polarization polarization can be +, 0, -can be +, 0, -

• New New COMPASS COMPASS results!results!

Courtesy Vogelsang and Stratmann

gqgq G

G

q

q

qqqqq

q

q

q

gggg G

G

G

G

ALL

Constraints on Constraints on gg((xx)) w/ w/ 00 Production Production

• pppp 00 XX is sensitive to is sensitive to gggggggg and and gqgqgqgq

PHENIX Results from Run-3Appeared in PRL

GeV 200at on tocontributi fractional 0 sXpp GeV 200at for :PHENIX 0 sXppALL

Trial Fit!Trial Fit!• Utilized NLO Utilized NLO 00 cal cal

culation (thanks to culation (thanks to Vogelsang and StrVogelsang and Stratmann) atmann) – to find “relevant-x” to find “relevant-x”

for each for each ppTT bin bin

• Only 4 data points:Only 4 data points:– gg//gg((xx)=)=ax+bax+b – 22/ndf~2.6/ndf~2.6– Sign undeterminedSign undetermined

• More precisision!More precisision!

0LLA

)GeV/( cpT

g

g

g

gALL

2

Near Future ofNear Future ofg/gg/g((xx))• PHENIX PHENIX 00

– Need global Need global QCD analysisQCD analysis

• Also coming Also coming soon from RHIC soon from RHIC are…are…– STAR jet & STAR jet & 00

– Prompt Prompt – Charm/BottomCharm/Bottom

• AndAnd– COMPASS charmCOMPASS charm– HERMES HERMES

deuterondeuteronCourtesy Vogelsang and Stratmann

Extend Extend xx RangeRange• AALLLL((00) from Run 6/) from Run 6/

7 (65 pb7 (65 pb-1-1) will exte) will extend nd xx range to larger range to larger xx

• STAR jet measuremSTAR jet measurement also provides prent also provides precision dataecision data

• 500 GeV run will co500 GeV run will cover smaller ver smaller xx-range-range

Prompt Photon Prompt Photon ProductionProduction• Gluon Compton DominatesGluon Compton Dominates

– 10% Contamination from Annihilation 10% Contamination from Annihilation – No fragmentation contribution in LONo fragmentation contribution in LO

i

)()(

)(

)(

)(

22

22

1

1 qgqaxqe

xqe

xg

xgA LL

ii

ii

i

LL

10.001

P1

P2

k2

k1

Direct photon in Run-2006/7Direct photon in Run-2006/7

P1

P2

k2

k1

Single Transverse-Single Transverse-SpinSpin AsymmetryAsymmetry

Single Transverse Spin Single Transverse Spin AsymmetriesAsymmetries• Fermilab E-704 reported LargFermilab E-704 reported Larg

e Asymmetriese Asymmetries AANN • Could be explained asCould be explained as

– Transversity x Spin-dep fragmentTransversity x Spin-dep fragmentation (Collins effect), ation (Collins effect),

– Intrinsic-Intrinsic-kkTT imbalance (Sivers eff imbalance (Sivers effect) , orect) , or

– Twist-3 (Qiu-Sterman, Koike)Twist-3 (Qiu-Sterman, Koike)– Or combination of aboveOr combination of above

GeV 4.19at sXpp Left Right

PHENIX Results: Central PHENIX Results: Central RapidityRapidity• ZERO asymmetry:ZERO asymmetry:

Charged hadrons

Neutral pions

h- h+

Polarization scaling error ~30% not included

0

PHENIX Preliminary

PHENIX Preliminary

AN for both charged hadrons and neutral pions consistent with zero.

STAR Results: Forward STAR Results: Forward RapidityRapidity• Large Asymmetry MeasuLarge Asymmetry Measuredred

• To distinguish models, jeTo distinguish models, jet axis reconstruction is rt axis reconstruction is requiredequired

• Probably…Probably…AANN requires lar requires large ge xxBJBJ, which is only achi, which is only achievable in hi-evable in hi-ppTT in Central in Central rapidity (small xsection)rapidity (small xsection)

• Global Analysis with HERGlobal Analysis with HERMES results would be beMES results would be beneficialneficial– Factorization has to be prFactorization has to be pr

oven!!!oven!!!

STARSTAR

STAR new Results on STAR new Results on AANN

• Significantly extenSignificantly extended kinematical cded kinematical coverage:overage:– More FWDMore FWD– Negative xFNegative xF

• g-g correlation smg-g correlation small? (Ji)all? (Ji)

ExploreExplore xxFF and p and pTT

h+h+ h-h-

pionpion 219K219K 216K216K

kaonkaon 46K46K 26K26K

protoprotonn

165K165K 17K17KIntegrated yields of , K and proton in xF range 0.15-0.35

xF and pT range of the data• PHENIX and STAR to ExPHENIX and STAR to Explore xplore xFF~0 and hi-p~0 and hi-pTT

• STAR and BRAHMS to STAR and BRAHMS to explore hi-xexplore hi-xFF and lo~mi and lo~mid-pd-pTT

• BRAHMS data being anBRAHMS data being analysed…alysed…

STARSTAR

Sea-Quark Sea-Quark PolarizationPolarization

W Production in pp CollisionsW Production in pp Collisions• WW is produced through pure V-A is produced through pure V-A

– Chirality is fixed Chirality is fixed ideal for spin structure studies ideal for spin structure studies

• WW couples to weak charge ~ flavor couples to weak charge ~ flavor– Flavor is (almost) fixed Flavor is (almost) fixed ideal for flavor structure ideal for flavor structure

studiesstudies

• Parity Violating Asymmetry Parity Violating Asymmetry AAL L ::

)()()()(

)()()()(

baba

babaWL xuxdxdxu

xuxdxdxuA

J. Soffer et al.

Sensitivity GoalSensitivity Goal• Studies with PHENIX MuStudies with PHENIX Mu

on Armson Arms– STAR Endcap Calorimeter STAR Endcap Calorimeter

provides similar sensitivitprovides similar sensitivityy

– AALL~~u/u(x)~u/u(x)~0.7-0.9 (!) at l0.7-0.9 (!) at large-arge-xx

– Central Rapidity covered bCentral Rapidity covered by both PHENIX and STARy both PHENIX and STAR

• What about What about ss????– Charm associated WCharm associated W R R

HIC IIHIC II

Hadron Collider Physics

TEVATRON LHC

Growing Fields…Growing Fields…

RHIC-SpinGluon PolarizationQuark PolarizationTransversityPol. FragmentationRole of Strangeness

Precision Structure Studies

Ongoing Spin Experiments　 COMPASS,HERMES　 JLab

Ongoing Unpolarized Studies　 HERA-II

Future Projects J-Parc,GSI -Factory?

EIC (ep, eA)? JLab-12?

Mechanism of Confinement　 Lattice-QCD 、 Effective Model

N elastic scattering

e+e- Data　… LEP, BELLE

Hi-E Heavy Ion Physics RHIC, LHC

Dark Matter

Neutron EDM

Precision,small-xLarge-x

Large-x

SummarySummary• RHIC Spin started to produce physics resultsRHIC Spin started to produce physics results

– PHENIX PHENIX 00 AALLLL Gluon Polarization Gluon Polarization – Single Transverse-Spin AsymmetrySingle Transverse-Spin Asymmetry

• Central Rapidity ~ 0Central Rapidity ~ 0• Forward: LargeForward: Large• Backward ~ 0Backward ~ 0

• Near future measurements onNear future measurements on– Gluon polarization, sea-quark, transversity and more! Gluon polarization, sea-quark, transversity and more!

• Stay tuned and Stay tuned and 謝謝！再見！謝謝！再見！

“Prospects for Spin Physics at RHIC” G. Bunce, N. Saito, J. Soffer and W. Vogelsang

Ann. Rev. of Nucl. And Part. Science 2000

AAC FrameworkAAC Framework(Asymmetry Analysis Collaboration)(Asymmetry Analysis Collaboration)

• Full respect to “what’s measured”Full respect to “what’s measured”– Use Use AA11((xx,,QQ22)) ～～ AA// // ((xx,,QQ22)) as input as input

• gg11((xx)) is affected by unpolarized is affected by unpolarized FF11((xx)=)=FF22((xx)/2)/2xx{1+{1+RR((xx)})}

– Include Systematic UncertaintiesInclude Systematic Uncertainties•Hard to separate correlated vs uncorrelated onesHard to separate correlated vs uncorrelated ones•Overestimate of uncertainties (Order ~10% on avg)Overestimate of uncertainties (Order ~10% on avg)

• Parametrize “polarization”Parametrize “polarization”– Easy to see the effects of choice of unpolarized Easy to see the effects of choice of unpolarized

PDFPDF)()1()( xfxNxxf

Polarised Parton DistributionsPolarised Parton Distributions• Global QCD Analysis to Extract Polarized QuaGlobal QCD Analysis to Extract Polarized Qua

rk and Gluon Distributions rk and Gluon Distributions – ((a laa la MRST, CTEQ) MRST, CTEQ)

• Four Independent Distributions are often extrFour Independent Distributions are often extracted – e.g. acted – e.g. UU((xx,,QQ22)),,DD( ),( ),S S ( ),( ), g g ( )( )– In unpolarised case, even more In unpolarised case, even more

• We have ONLY TWO independent measuremWe have ONLY TWO independent measurements ents gg11

pp((xx, , QQ22) and ) and gg11nn((xx,,QQ22))

– QQ22 evolution helps? evolution helps?

gtbcssdduu ,,,,,,,,,

Precision QCD test for Hadron PrdctnPrecision QCD test for Hadron Prdctn• pppp 00 X @ 200 X @ 200

GeV (PHENIX)GeV (PHENIX)• Cross Section is Cross Section is

well described bwell described by the pQCD over y the pQCD over 8 order of magni8 order of magnitude!tude!

• STAR STAR 00 Results Results also agree!also agree!

PHENIX PRL (2004)

Good agreementwith NLO pQCD

J.Sowinski’s talk

STARSTAR

ForwardForward Inclusive Cross SectionInclusive Cross Section

STAR data consistent with Next-to-Leading Order pQCD calculations

in contrast to data at lower s (Bourelly and Soffer, Eur.Phys.J. C36 (2004) 371-374)

• STAR data at

= 3.8 (hep-ex/0310058, Phys. Rev. Lett. 92 (2004) 171801)

• = 3.3 (hep-ex/0403012, Preliminary)

• NLO pQCD calculations at fixed with equal factorization and renormalization scales = pT

• Solid and dashed curves differ primarily in the g fragmentation function

STARSTAR

First Prompt First Prompt Results @ 200 GeV Results @ 200 GeV

• RHIC Spin Gold plRHIC Spin Gold plated mode for ated mode for g g started! started!

• pQCD describes repQCD describes results very well!sults very well!

• Ready for Ready for AALLLL!!

• See talk by K. OkaSee talk by K. Okada in //-session 2da in //-session 2

Xpp

AANN in in pp pp pppp and and ppCCppCC• Hadronic Spin Flip Exist : Hadronic Spin Flip Exist : ppC >> C >> pppp

GeV 200 E704 FNAL

GeV 100Jet -pol RHIC

beam

beam

P

P

preliminarypppp

preliminary

GeV 100

GeV 22

beam

beam

P

P

CC pp

r5=0

H. Okada’s talk in //session-4 O. Jinnouchi’s talk in //session-4

• Hadron Spin Hadron Spin Flip existsFlip exists

• Indicating hiEIndicating hiE>loE???>loE???

• Need to ExplNeed to Explore!!!ore!!!

• See I.AlekseSee I.Alekseev’s talk in /ev’s talk in //session-4!/session-4!

AANN in in pp pp pppp in Hi-Energy in Hi-Energy

Statistical errors only

GeV 200@ spppp

AANN in FWD neutron production in FWD neutron production• Large Asymmetry discovered (~3mrad) : Large Asymmetry discovered (~3mrad) : AANN~ -10%~ -10%• Xsection(ISR) reproduced with OPE=Fully Spin Flip!Xsection(ISR) reproduced with OPE=Fully Spin Flip!

deg0~@nXpp

onpolarizati 70%with

GeV 500at pb800

GeV 200at pb320

assuming

1

1

sLdt

sLdt

W Production in pp CollisionsW Production in pp Collisions• WW is produced through pure V-A is produced through pure V-A

– Chirality is fixed Chirality is fixed ideal for spin structure studies ideal for spin structure studies

• WW couples to weak charge ~ flavor couples to weak charge ~ flavor– Flavor is (almost) fixed Flavor is (almost) fixed ideal for flavor structure ideal for flavor structure

studiesstudies

• Parity Violating Asymmetry Parity Violating Asymmetry AAL L ::

)()()()(

)()()()(

baba

babaWL xuxdxdxu

xuxdxdxuA

J. Soffer et al.

Sensitivity GoalSensitivity Goal• Studies with PHENIX MuStudies with PHENIX Mu

on Armson Arms– STAR Endcap Calorimeter STAR Endcap Calorimeter

provides similar sensitivitprovides similar sensitivityy

– AALL~~u/u(x)~u/u(x)~0.7-0.9 (!) at l0.7-0.9 (!) at large-arge-xx

– Central Rapidity covered bCentral Rapidity covered by both PHENIX and STARy both PHENIX and STAR

RHIC Spin and HERMES SIDISRHIC Spin and HERMES SIDIS• Complementary!Complementary!

– RHIC WRHIC W•No fragmentation amNo fragmentation am

biguitybiguity• xx-range limited-range limited•Useless for transversiUseless for transversi

ty studiesty studies•Otherwise Otherwise WWRR!!

– HERMES Semi-InclusHERMES Semi-Inclusive DISive DIS•Wide Wide xx-range-range•Could be used for traCould be used for tra

nsversity studiesnsversity studies

Transversity MeasurementsTransversity Measurements• Drell-Yan Production of Lepton PairsDrell-Yan Production of Lepton Pairs

– Clean, but low statistics (Clean, but low statistics (QEDQED process) process) – Precision will be improved by Precision will be improved by LL upgrade upgrade

ii

ii

TTTT xqxqe

xqxqeaA

)21()()(

)21()()(

212

212

PHENIX Muon200 GeV

O. Martin, A. Schaefer, M. Stratmann, W. Vogelsang PRD60 (99) 117502

Transverse Jet Transverse Jet ProductionProduction

• Advantages:Advantages:– Enormous yield could ovEnormous yield could ov

ercome the smallness of ercome the smallness of asymmetriesasymmetries

– No mixture with Gluonic No mixture with Gluonic contributioncontribution

• Caveats:Caveats:– Control of systematics wiControl of systematics wi

ll be the key for the succll be the key for the successess• AATTTT~0.2% = 0.1% (if P~0.2% = 0.1% (if PBB=7=7

0%)0%)

– AATTTT is cos2 is cos2 moment: sta moment: statistics will be divided into tistics will be divided into several several -bins-bins

Single Transverse Spin Single Transverse Spin AsymmetriesAsymmetries• If we have analyzer of final state quark polarizationIf we have analyzer of final state quark polarization

……– We can use Spin We can use Spin Transfer Double Transfer Double Spin Asymmetry Spin Asymmetry to probe Transversity!to probe Transversity!

• Spin Dep. Frag. Fn.Spin Dep. Frag. Fn. Can be studied in Can be studied in e+e- collisionse+e- collisions BELLEBELLE HERMES IFFHERMES IFF

Spin Transfer Double Spin Asymmetry

- 1

- 0.8

- 0.6

- 0.4

- 0.2

0

0.2

0.4

0.6

0.8

1

- 1 - 0.5 0 0.5 1

cos q

aTT(if)

qgqqqq'qqbarFn.) Frag. Dep.Spin (

)(1

if

TTT axhA

Searches for New PhysicsSearches for New Physics• Anomalous Parity Violation iAnomalous Parity Violation i

n Jet Production n Jet Production – Contact Interaction (Scale Contact Interaction (Scale ))

• CDFCDF>1.8 TeV (obsolete)>1.8 TeV (obsolete)• D0 D0 >2.4 TeV (obsolete)>2.4 TeV (obsolete)• RHIC Spin Reach RHIC Spin Reach ~3.3 TeV~3.3 TeV

– New Gauge Boson Z’New Gauge Boson Z’• Need higher energy to proviNeed higher energy to provi

de useful informationde useful information• But see T.Gehrmann’s new But see T.Gehrmann’s new

workwork

RHIC Spin RoadmapRHIC Spin RoadmapYearYear P(%)P(%) WeeksWeeks

(Com/Ph)(Com/Ph)LumiLumi CM CM

EnergyEnergyGoals Goals

20022002 2020 8 (5/3)8 (5/3) 0.15 pb0.15 pb-1-1 200 GeV200 GeV Transverse Spin Transverse Spin

Systematic StudiesSystematic Studies

20032003 3030 8 (5/3)8 (5/3) 0.35 pb0.35 pb-1-1 200 GeV200 GeV Longitudinal SpinLongitudinal Spin

Gluon Polarization?Gluon Polarization?

20042004 5050 5(5/0) 5(5/0)

0.15 pb0.15 pb-1-1 200 GeV200 GeV RHIC Commissioning RHIC Commissioning

Polarized Gas Jet Polarized Gas Jet TargetTarget

20052005 6060

10 pb10 pb-1-1 200 GeV200 GeV

500 GeV500 GeVGluon Polarization/Transv.Gluon Polarization/Transv.Commissioning-1?Commissioning-1?

2006/2006/77

7070

~100 pb~100 pb--

11

pbpb-1-1

200 GeV200 GeV500 GeV500 GeV

Gluon Polarization/Transv.Gluon Polarization/Transv.Commissioning-2?Commissioning-2?

2008/2008/99

7070 ~350 pb~350 pb--

11

500 GeV500 GeV W-Physics/Transv.W-Physics/Transv.

PHENIXPHENIX STARSTAR

Fwd Cal, MRPC-TOFFwd Cal, MRPC-TOF

VTX, Muon Trigger, FwVTX, Muon Trigger, Fwd Cald Cal

DAQ/FEE-1KHz, HFT, DAQ/FEE-1KHz, HFT, Fwd TrkerFwd Trker

M.Togawa, E. Kinney and J.Sowinski’s talk in //session-2

FAQs on Gluon SpinFAQs on Gluon Spin• Gauge Invariant?Gauge Invariant?

– Yes; Gauge Invariant but Non-Local OperatorYes; Gauge Invariant but Non-Local Operator• At At AA+=0+=0 Gauge, it collapses to a Local Operator Gauge, it collapses to a Local Operator

• Any estimate from Lattice?Any estimate from Lattice?– There are some difficulties: Non-Local; There are some difficulties: Non-Local; AA+=0+=0 Gauge Gauge

• What Effective Model says?What Effective Model says?– Bag & NR-Quark Model : Bag & NR-Quark Model : gg < 0 Jaffe < 0 Jaffe– Chiral Quark Model : Chiral Quark Model : gg ~ ~ q q > 0 > 0 Lee, Min, Park, Rho Lee, Min, Park, Rho

• What Global QCD Analyses say?What Global QCD Analyses say?– AAC03 AAC03 : : gg = 0.50±1.27 = 0.50±1.27– BBA BBA : : gg = 1.026 ± 0.549 = 1.026 ± 0.549 – BBBBBB : : gg = 0.031 ± 0.669 = 0.031 ± 0.669

PSAFPSM

GA

k

kk 0

2,1

)0()0(~

2

1

Jaffe

FAQs on Gluon Spin cont’FAQs on Gluon Spin cont’• How we can obtain How we can obtain gg//gg((xx) from ) from AALLLL((00)?)?

– Should be done with “state-of-art” NLO QCD AnalysesShould be done with “state-of-art” NLO QCD Analyses• Any Poorman’s solution for experimentalists?Any Poorman’s solution for experimentalists?

– Probably yes, but should not be stretched too much…Probably yes, but should not be stretched too much…

• Caution:Caution:– Do not ask for first moment of Do not ask for first moment of gg((xx))

– Do not ask for systematic errors in the methodDo not ask for systematic errors in the method

• Why am I going to show?Why am I going to show?– To provide some idea on possible uncertainties To provide some idea on possible uncertainties – To emphasize importance of various spin asymmetry meTo emphasize importance of various spin asymmetry me

asurementsasurements

ApproximationApproximation• Start from Start from

dzDdt

dxqxq

dzDdt

dxqxgdzD

dt

dxgxgpA

d

ddTLL

)()()(

)()()()()()()(

21

2121

• In the central rapidity In the central rapidity xx11~~xx22 dominates dominates

• With “Mean Value Theorem” for multiple With “Mean Value Theorem” for multiple integration, integration,

)()()()()(~)(2

TTTTLL pg

gp

g

gppA

• Find Find and and from from AALLLL with various with various gg//gg((xx) ) (Many thanks to Marc(Many thanks to Marco and Werner!)o and Werner!)

Test of the MethodTest of the Method• Use GRSV-std as an iUse GRSV-std as an i

nput to calculate nput to calculate AALLLL

• Use resulted Use resulted AALLLL to e to extract xtract gg//gg((xx)) to see i to see if it agrees with the orf it agrees with the original GRSV-stdiginal GRSV-std

• Not badNot bad• AALL LL ((00) alone cannot ) alone cannot

determine sign of determine sign of gg//gg((xx))

Prompt Photon Prompt Photon Production Production

• Gold Plated mode for Gold Plated mode for gg((xx))

x-reconstructed using jet

xW. Vogelsang et al.

L. Bland

PHENIX STAR

Impact of Impact of ss Measurement Measurement• Improve Knowledge on Spin Flavor Structure of Improve Knowledge on Spin Flavor Structure of

the Proton the Proton – Beyond Flavor SU(3) assumptionBeyond Flavor SU(3) assumption

• Neutron EDM Neutron EDM – nn-EDM predicted -EDM predicted using q-EDM and using q-EDM and qq

• Dark Matter Dark Matter – Better determination of Dark-Matter reactionBetter determination of Dark-Matter reaction

smdmum

sdddudd

sdu

Es

Ed

Eu

En

)(

J.Ellis and R.A.Flores PLB377(96)83

J.Ellis and M. Karliner Lecture at Erice School 95 hep-ph/9601280

gaugino) (1) (pure )(36

5

36

17

or (photino) )(9

1

9

4)(

Usdu

sdupp

NN Elastic Scattering Elastic Scattering• Cross section for Cross section for NN elastic Scattering elastic Scattering

– Where (Where (QQ22 dropped for brevity) dropped for brevity)

22

22

22

2

4/);/(4

2

pp

F

MQMEW

CWBWAE

QG

dQ

d

212

22

12

1 4)1()1(4

1FFFFGA

2114

1FFGB

22

21

212

2

16

1FFG

Q

MC p

for ;for

2

)(

)/1(

631.0)(

21

2222

1

QG

MQQG

s

A

sG s )0(1

kk’

qP P’

BNL-Experiment 734BNL-Experiment 734

• Measured elastic scatterMeasured elastic scattering cross sectioning cross section

and and – Liquid scintillator + Drift TLiquid scintillator + Drift T

ube 170 tube 170 t– 0.5E19 POT for neutrino 0.5E19 POT for neutrino

and 2.5E19POT for anti-nand 2.5E19POT for anti-neutrinoeutrino

– QQ22>0.40 GeV>0.40 GeV22

(L.A.Ahrens et.al PRD35(87)785; Reanalysis G.T. Garvey et. al PRC48(93)761)(L.A.Ahrens et.al PRD35(87)785; Reanalysis G.T. Garvey et. al PRC48(93)761)

pp pp Too High Q2 Cut-off

79% from Carbon

Go to lower Q2

Extract Pure Proton

NN-Elastic Scattering Exp at J-PARC-Elastic Scattering Exp at J-PARC

• On-axis at near detector hall for T2K ExperimeOn-axis at near detector hall for T2K Experimentnt

• Utilize both two types of LiqScintillator with diffUtilize both two types of LiqScintillator with different erent H/CH/C mixture for pure proton signal mixture for pure proton signal– e.g Bicron BC510A (e.g Bicron BC510A (H/CH/C=1.212) and BC-533 (=1.212) and BC-533 (H/CH/C

=1.96)=1.96)– Pure Carbon can be extracted for Pure Carbon can be extracted for A XsectionA Xsection– e.g. 5x5x5me.g. 5x5x5m33 ~ 125 t ~ 125 t

• 1E21 POT possible in one year (130 days)1E21 POT possible in one year (130 days)– 30 times BNL-E73430 times BNL-E734– Better with polarity change for Better with polarity change for and v

Sensitivity for Sensitivity for ss• AssumptionsAssumptions

– Similar Detection Efficiency Similar Detection Efficiency to E734: to E734: • 7.6% for neutrino-N elastic7.6% for neutrino-N elastic• 5.4% for anti-neutrino-N elastic5.4% for anti-neutrino-N elastic

– However with lower QHowever with lower Q22 cut- cut-off : 0.1 GeVoff : 0.1 GeV22

• Achievable with more uniform Achievable with more uniform detector ?detector ?

– 25 times more statistics but 25 times more statistics but pure proton only 1/6pure proton only 1/6• Factor 2 reduction in statistical Factor 2 reduction in statistical

error error – Systematic control Systematic control

improvements to ~5% improvements to ~5% • E734 7.6% dominated by Beam E734 7.6% dominated by Beam

Flux and Nuclear Effects Flux and Nuclear Effects • Possible to remove Nuclear Possible to remove Nuclear

Effects which could be larger in Effects which could be larger in lower Qlower Q22 region region

Comparison with E734Comparison with E734• If If ss is the only parameter is the only parameter

to be determinedto be determined– E734: E734: – J-PARC: J-PARC:

• But… But… ss and and MMAA coupled coupled significantly significantly – E734: E734: – J-PARC: J-PARC: – N.B. other analysis of E734 N.B. other analysis of E734

provided better precision: provided better precision: =

-s

/gA(=

1.25

6)08.010.0 s03.010.0 s

27.010.0 s12.010.0 s

Better determination of s with Significantly improved Sytematics

Separation with MA might be Problematic

Other Existing EffortsOther Existing Efforts• Semi-Inclusive DISSemi-Inclusive DIS

– DESY-HERMES and CERN-COMPASSDESY-HERMES and CERN-COMPASS– Subject to FF Uncertainties: BELLE measurement of FFSubject to FF Uncertainties: BELLE measurement of FF– Limited in x-regionLimited in x-region

• RHIC Spin (Polarized pp Collider at BNL)RHIC Spin (Polarized pp Collider at BNL)– Clear determination of u-bar and d-bar with W productioClear determination of u-bar and d-bar with W productio

n, however limited in x-regionn, however limited in x-region– Measurement of Measurement of s requires charm-associated W producs requires charm-associated W produc

tion : small xsectiontion : small xsection• FINeSSE experiment proposed at FNAL; BNLFINeSSE experiment proposed at FNAL; BNL

– Extend to lower Extend to lower QQ22 (as we discussed) (as we discussed) – Seem to propose only neutrino measurementsSeem to propose only neutrino measurements

• Only quadratic combination will be determined Only quadratic combination will be determined subject to two subject to two solution problemsolution problem

– Subject to Nuclear Effects (Liq Scintillator) Subject to Nuclear Effects (Liq Scintillator)

Experimental Issues – (1)Experimental Issues – (1)• Low Low QQ22 measurement measurement

– QQ22=2=2MMppEEpp; ; QQ22=0.1GeV=0.1GeV22 EEpp=50 MeV =50 MeV

– energy resolution will affect xsection esp. in low energy resolution will affect xsection esp. in low QQ22

Ep=100 MeV

Experimental Issues – (2)Experimental Issues – (2)

• Control of BackgroundControl of Background– Coherent Pion productionCoherent Pion production

• Better momentum analysis of Better momentum analysis of from CC from CC– Magnet? Or Range? Magnet? Or Range?

• Work is underway to define Work is underway to define – Scope of the experimentScope of the experiment– The experimental setupThe experimental setup

Other physics topics to be Other physics topics to be investigatedinvestigated• Neutrino-Nuclear cross Neutrino-Nuclear cross

sectionsection– Interesting by its own; imInteresting by its own; im

portant subject of Nucleaportant subject of Nuclear/Hadron Physicsr/Hadron Physics

– Also provide a better conAlso provide a better control in oscillation physicstrol in oscillation physics

• Weak-Mixing Angle meaWeak-Mixing Angle measurementssurements– Low-Q2 determination of Low-Q2 determination of

sinsin22WW

– Interests triggered by NuInterests triggered by NuTeV, Atomic PV, and PV iTeV, Atomic PV, and PV in eN scattering n eN scattering

– Q: Testing EW? Or TestinQ: Testing EW? Or Testing Hadron Physics? g Hadron Physics?

Proton Spin Sum RuleProton Spin Sum Rule• Quark/Gluon Spin and Orbital Angular Mom.Quark/Gluon Spin and Orbital Angular Mom.

)3 if( 18.0163

3

2

1

2

1

f

f

fq n

n

nL

)3 if( 32.0163

16

2

1

f

fg n

nLg

gq

proton

LLg 2

1

2

1

Ji, Tang, and Hoodboy

• Only Only measured; but we have some measured; but we have some constraintsconstraints

Single Transverse Spin Single Transverse Spin AsymmetryAsymmetry• Non-zero Single Transverse Spin Non-zero Single Transverse Spin

Asymmetry (SSA) requiresAsymmetry (SSA) requires– Spin Flip AmplitudeSpin Flip Amplitude– Phase difference Phase difference

2/

2/

i

i

Spin Flip!

Map out the Nucleon Map out the Nucleon StructureStructure• Generalized Generalized

Partonic PictPartonic Picture of the Nure of the Nucleonucleon

• Transverse Transverse