Spin Physics Results from RH Spin Physics Results from RH IC IC International conference on QCD and Hadr International conference on QCD and Hadr on Physics on Physics June 16-20, 2005, Beijing June 16-20, 2005, Beijing Naohito SAITO Naohito SAITO (Kyoto University) (Kyoto University)
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Spin Physics Results from RHIC International conference on QCD and Hadron Physics June 16-20, 2005, Beijing Naohito SAITO (Kyoto University)
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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
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
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.
– 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
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
• 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!
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
• 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
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
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
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
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)