Recent PHENIX Spin Recent PHENIX Spin ResultsResults

Astrid MorrealeAstrid Morreale

University of California at RiversideUniversity of California at Riverside

On behalf of the collaborationOn behalf of the collaboration

WWND, April 12, 2008

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OutlineOutline

About About polarized polarized RHIC, PHENIXRHIC, PHENIX The Proton Spin Structure via The Proton Spin Structure via

AsymmetriesAsymmetriesRecent PHENIX results from polarized Recent PHENIX results from polarized

proton running proton running (longitudinal, transverse if time (longitudinal, transverse if time permits)permits)

Summary Summary

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RHICRHIC

Acceleration of polarized protons between 25 and 250 GeVAcceleration of polarized protons between 25 and 250 GeV Up to 120 Bunches with 2*10Up to 120 Bunches with 2*101111 protons (100ns apart) protons (100ns apart) Polarization up to 70%Polarization up to 70% http://www-nh.scphys.kyoto-u.ac.jp/SPIN2006/SciPro/pres/plenary/MeiBai.ppthttp://www-nh.scphys.kyoto-u.ac.jp/SPIN2006/SciPro/pres/plenary/MeiBai.ppt

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scatteredproton

recoilCarbon

polarizedbeam

Carbontarget

PolarimetryPolarimetry ““CNI”-Polarimeter measures left-right asymmetries in CNI”-Polarimeter measures left-right asymmetries in

elastic pC collisionselastic pC collisionso Provides fast relative polarization measurementProvides fast relative polarization measuremento Scan polarization over x and y range of the beamScan polarization over x and y range of the beam

270.352002003 *

400.122002004 *

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55

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Polarization [%]

0.0862.42006 *

7.52002006 *

3.42002005 *

Luminosity [pb-1] (recorded)[GeV]Year

Forward scattered proton

proton target

proton beam

““Jet” Polarimeter measures left-right asymmetries in elastic pp Jet” Polarimeter measures left-right asymmetries in elastic pp collisions collisions

oUses the known polarization of H atoms from Atomic Beam SourceUses the known polarization of H atoms from Atomic Beam Source

oAbsolute measurementAbsolute measurement

oIntegrating over beam profileIntegrating over beam profile

oRun 6: total syst. polarization uncertainty Run 6: total syst. polarization uncertainty PPBBPPYY/(P/(PBBPPYY)=8.4%)=8.4%

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The PHENIX Detector for Spin PhysicsThe PHENIX Detector for Spin PhysicsCentral Detector Central Detector Acceptance: (|Acceptance: (|||x x ::• High efficiency High efficiency trigger trigger • detectiondetection

– Electromagnetic Calorimeter:Electromagnetic Calorimeter: PbSc + PbGl, PbSc + PbGl, < |0.35|, < |0.35|, = 2 x 90 = 2 x 90

• ee++/e/e--

– Drift ChamberDrift Chamber– Ring Imaging Ring Imaging ČČerenkov erenkov

Detector(RICH) Detector(RICH)

Muon Arms Muon Arms (forward kinematics (~1.1<| (forward kinematics (~1.1<| |<2.4) |<2.4)::

•JJ–Muon ID/Muon Tracker (Muon ID/Muon Tracker ())

•

–Electromagnetic Calorimeter (MPC)Electromagnetic Calorimeter (MPC)

Global Detectors:Global Detectors:

•Relative LuminosityRelative Luminosity

–Beam-Beam Counter (BBC) Beam-Beam Counter (BBC)

Zero-Degree Calorimeter (ZDC)Zero-Degree Calorimeter (ZDC)

•Local Polarimetry - ZDCLocal Polarimetry - ZDC

Intrinsic Spin Violates our intuition:

How can an elementary particle such as the e¯ be point like and have perpetual angular momentum.?

The Proton also violates our intuition.The Proton is composed of quarks, gluons and anti quarks.

We should expect the proton's spin to be predominatelycarried by its 3 valence quarks

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That nucleon has a large anomalous magnetic moment proves that this is not a fundamental spin1/2 Dirac particle.

Within the nucleon:Quarks, gluons and their angular momentum caused by their high speed motion within the nucleon are contributors to the Nucleon's spin.

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Contributions to the Proton's Contributions to the Proton's Spin Spin

Quarks and Gluons carry about 50%(each) of the Quarks and Gluons carry about 50%(each) of the longitudinal momentumlongitudinal momentum

What about Spin?What about Spin?

Valence Quarks (QPM) Valence Quarks (QPM) ~30%~30%

((QQCCDD) Gluons, Sea Quarks: ) Gluons, Sea Quarks: ~>, =, ~>, =, <0?<0?

Orbital Angular Momentum Orbital Angular Momentum ~?~?

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The Spin Structure of the ProtonThe Spin Structure of the ProtonLongitudinal Spin Sum Rule:

Transverse Spin Sum Rule?

12=S z=

12

ΔΣ+ΔG+L z

12=S x=

12δΣ+L x

Double Spin Asymmetries (pp,SIDIS)

W-production (pp)

Exclusive processes (DVCS,etc)

Chiral-odd Fragmentation functions (Collins,IFF,L)

Sivers effect??

ΔG, Δq=are the probabilities of finding a parton with spin parallel or anti parallel to the spin of the nucleon.

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Accessing Accessing g with Asymmetriesg with Asymmetries

I Hard subprocess asymmetries (LO)

Increasing x, pT

1 2LL LL

1 2

g(x ) q(x )ˆA a (qg q )

g(x ) q(x )

ˆ ˆ

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AsymmetriesAsymmetries For our For our g program the tools are measurements of g program the tools are measurements of

helicity cross section asymmetries Ahelicity cross section asymmetries ALLLL

Bunch spin configuration alternates every 106 ns

Data for all bunch spin configurations are collected at the same time

Possibility for false asymmetries are greatly reduced

(N) Yield (R) Relative Luminosity

BBC vs ZDC(P) Polarization

RHIC Polarimeter (at 12 o’clock)Local Polarimeters (SMD&ZDC)

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AsymmetriesAsymmetriesAccessing Accessing g: g: Inclusive channels AInclusive channels ALLLL(pp(ppAX) AX)

measurable at Phenixmeasurable at Phenix 00: wide p: wide pTT range, mixture with gg range, mixture with ggX dominant at low X dominant at low

ppTT , similar to , similar to 0 , 0 , different FF’s. different FF’s. , mixture sensitive to qg, mixture sensitive to qgqX at high pqX at high pTT

o Multiparticle clusters (parts of jets), correlated with Multiparticle clusters (parts of jets), correlated with 0,0,

o Direct photons: pDirect photons: pTT range 6-20+ GeV/c, dominated by range 6-20+ GeV/c, dominated by qgqgqq

o J/J/, , , e, e (gg (ggcc)cc)

LLzz : Current k : Current kT,T, , D , DLL, A, AN,UT, TN,UT, T

measurements at Phenixmeasurements at Phenixo AANN π π00/π/π//hh, J/, J/forward neutrons forward neutrons o DLL Anti-Λ Spin Transfero kkTT azimuthal di-h azimuthal di-h correlations correlations

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00 cross section cross section measurementmeasurement

Agreement between Agreement between data and pQCD data and pQCD theorytheory

Shows that pQCD Shows that pQCD and and unpolarizedunpolarized PDFs determined in PDFs determined in DIS can describe pp DIS can describe pp datadata

Choice of Choice of fragmentation fragmentation function crucial function crucial (dominated by gluon (dominated by gluon fragmentation)fragmentation)

Scale uncertainty Scale uncertainty still large at lower still large at lower ppTT<5 GeV<5 GeV

PHENIX: 0 mid-rapidity, 200GeVhep-ex-0704.3599

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Measured asymmetries for pp0X from Run 5 ,Run 6

Run3,4,5: PRL 93, 202002; PRD 73, 091102; hep-ex-0704.3599

00 Asymmetries Asymmetries

Asymmetry of combinatorial Asymmetry of combinatorial background estimated from background estimated from sidebands and subtractedsidebands and subtracted

Initial state parton configurations contributing to unpolarized cross

section (Fractions)

W. Vogelsang et al. Dominated by gg for pT<3, qg

for 3<pT<10 GeV/c

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Information from Information from 00 AsymmetriesAsymmetries

vs. xT=2pT/S

Maximum scenarios ruled out -> Constrain of Maximum scenarios ruled out -> Constrain of g(x) g(x) Inclusive Inclusive 00 A ALLLL cannot access cannot access g(x) directlyg(x) directly

o Only sensitive to an average over a wide x range Only sensitive to an average over a wide x range o No conclusions about moment of No conclusions about moment of g(x) possible without a g(x) possible without a

model for its shapemodel for its shape

More (indirect) information from varying cms energiesMore (indirect) information from varying cms energiesoHigher (500 GeV) Higher (500 GeV) lower x lower x

oSmaller (62 GeV) Smaller (62 GeV) higher x (and larger scale higher x (and larger scale uncertainty)uncertainty)

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+,-+,- Asymmetries Asymmetries

New set from M. Stratmann et al. is the first to use charged separated data from SIDIS for fragmentation functions

Charged pions above 5 GeV/c Charged pions above 5 GeV/c identified with RICH. identified with RICH.

At higher pAt higher pTT, qg interactions , qg interactions become dominant: become dominant: qqg term.g term.

AALLLL becomes significant allowing becomes significant allowing access to the sign of access to the sign of GG

Tp ~ 5GeV

+ 0 -

+ 0 -u u u

LL LL LL

qg starts to dominate for and D D >DExpect sensitivity to sign of G, e.g., positive A A A

Fraction of pion production

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Information from Information from +,-+,- AsymmetriesAsymmetries

Inclusive Inclusive +,-,0+,-,0 A ALLLL has access to sign has access to sign g(x) directlyg(x) directly “Model independent” conclusion possible once enough

data is available.

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Recent preliminary extraction of fragmentation functions, Eta has (slightly) enhanced sensitivity to gg (when compared to the 0 ) Observation of difference in asymmetries could help disentangle the contributions from the different quarks and the gluons.

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AsymmetriesAsymmetries

Dominated by qg Compton:- Small uncertainty from FFs- Better access to sign of G (qG)-Clean “Golden Channel” :-)-Luminosity Hungry :-(

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Information from Information from ee+,-+,- Asymmetries Asymmetries

Provide access different x Provide access different x rangerange

o Thresholds Thresholds o J/J/range (forward arms)range (forward arms)o PromptPrompt: no fragmentation z=1: no fragmentation z=1o Rare channels with large backgroundRare channels with large backgroundo Need more luminosityNeed more luminosity

prompt photon

cceX

bbeXJ/

xG

(x)

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G(x) Global Analysis

Results from various channels combined into single results for G(x) Correlations with other PDFs for each channel properly accounted Every single channel result is usually smeared over x global

analysis can do deconvolution (map of G vs x) based on various channel results

NLO pQCD framework can be used Global analysis framework already exist for pol. DIS data and being

developed to include RHIC pp data, by different groups

Now Run5-Final and Run6-Preliminary 0 data are available and has joined this effort

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G(x) Global AnalysisLatest Results

Global Analysis of Helicity Parton Densities and Their Uncertainties

(de Florian, Sassot, Stratmann and Wogelsang) ArXiv:0804.0422 (April 2008)

-Flavor dependence of the sea -SU3 symmetry breaking?.

“We also find that the SIDIS data give rise to a Robust pattern for the sea polarizations, clearly deviating from SU(3) symmetry, which awaits further clarification from the upcoming W boson Program at RHIC”

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G(x) Global AnalysisLatest Results

ArXiv:0804.0422 (April 2008)

-A first demonstration that p-p data can be included in a consistent way in a NLO pQCD calculation.

-RHIC data set significantly constraints on the gluon helicity distribution

-”Inclusion of theoretical uncertainties and the treatment of experimental ones should and will be improved”

hep-ex/0507073(hep-ex/0507073)

Transverse SpinTransverse Spin

(Collins effect)spin-dependentfragmentation

functions

(Sivers effect)transversely asymmetric

kt quark distributions

(Twist-3)quark gluon field

Interference

^ q1Tq,f ,L

• Mid-rapidity data at small pT sensitive to gluons, constrains magnitude of gluon Sivers function (Anselmino et al., PRD 74, 2006)•What happens if qq sets in (valence quarks) at high pT?

process contribution to 0, =0, s=200 GeV

PLB 603,173 (2004)p+p0+X at s=200 GeV/c2

PRL 95, 202001 (2005)

Transverse Spin Transverse Spin Mid-rapidity AMid-rapidity ANN of of 00 and h and h for y~0 for y~0 at at s=200GeVs=200GeV

AN is 0 within 1% interesting contrast with forward

AN : h+/h-

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Transverse Spin Transverse Spin 00 A ANN at large x at large xFF

3.0<<4.0

p+p0+X at s=62.4 GeV

p+p0+X at s=62.4 GeV

Asymmetry seen in yellow beam (positive xF), but not in blue (negative xF)Large asymmetries at forward xF Valence quark effect?xF, pT, s, and dependence provide quantitative tests for theories

process contribution to 0, =3.3, s=200 GeV

PLB 603,173 (2004)

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Transverse Spin Transverse Spin AANN of of J/J/ at at s=200GeVs=200GeV

Sensitive to gluon Sivers as Sensitive to gluon Sivers as produced through g-g produced through g-g fusionfusion

Charm theory prediction is Charm theory prediction is availableavailableo How does J/How does J/production production

affect prediction?affect prediction?

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Transverse Spin Transverse Spin Other asymmetries at Other asymmetries at s=200GeVs=200GeV

neutronchargedparticles

Run 5

Strange quark Components via Spin Strange quark Components via Spin TransferTransferIn PHENIX the Self-analyzing decay channel (anti-Λ) has been found to be sensitive to the polarization of the anti-strange sea of the nucleon (See: hep-ph/0511061)

Probing Orbital angular Momentum with kProbing Orbital angular Momentum with kTT Asymmetries Asymmetries (See:(See: Phys. Rev. D 74, 072002 (2006)

Neutron asymmetries. Neutron asymmetries. (See:(See:AIP Conf.Proc.915:689-AIP Conf.Proc.915:689-

692,2007692,2007 ))

Results for <jT2> Results for <kT2>

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SummarySummary PHENIX is well suited to the study of spin physics with a wide PHENIX is well suited to the study of spin physics with a wide

variety of probes.variety of probes.o Inclusive Inclusive 00 data for A data for ALLLL has reached statistical significance to has reached statistical significance to

constrain ΔG in a limited x-range (~0.02-0.3).constrain ΔG in a limited x-range (~0.02-0.3).

NeedNeed more statistics (RHIC running time) to explore more statistics (RHIC running time) to explore different (rare) channels fordifferent (rare) channels foro Different gluon kinematicsDifferent gluon kinematicso Different mixtures of subprocessesDifferent mixtures of subprocesses

Global Analysis of many channels together with DIS, SIDIS Global Analysis of many channels together with DIS, SIDIS data will give us a more accurate picture of data will give us a more accurate picture of g(x)g(x)

Upcoming Upcoming W programW program will give more information about will give more information about quarksquarks

PHENIX has an upgrade program that will give us the triggers PHENIX has an upgrade program that will give us the triggers and vertex information that we need for precise future and vertex information that we need for precise future measurements measurements

of of G, G, q and new physics at higher luminosity and energyq and new physics at higher luminosity and energy

We Think That We Understand the Concept of “Rotational Motion“

...but how does it workout at scales of about one fermi? (Marco Stratman. Lectures on the Longitudinal Spin Structure of the Nucleon, Wako, Japan)

We Should Measure it and find out!!

THANK YOU For Listening

THANK YOU For Listening

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ExtrasExtras

1p

Phys Rev D41 (1990) 83; Phys Rev D43 (1991) 261

Top view

^ q1q kpxp

1S

Quark transverse momentum in transversely polarized proton.

Front view

zyx

y

xz

Sivers effect: Initial stateInitial state of the polarized nucleon

x is longitudinal momentum fraction.

1p

Collins Heppelmann effect:Collins Heppelmann effect:Final stateFinal state of fragmentation hadrons of fragmentation hadrons

Example:: Xhhpp 21

Polarization of struck quark which fragments to hadrons.

Nucl Phys B396 (1993) 161, Nucl Phys B420 (1994) 565

'qp

1h

2h

21 hh

1S

Sivers effectSivers effect and/or and/or Collins- HeppelmannCollins- Heppelmann effect? effect?

Theoretical approaches to explain huge SSAs:

Sivers effect ( is connected to quark orbital angular momentum).

Collins effect (Analyzer of transversity q).

Twist3 effect which is related to both initial and final states. Relation of Twist3 to Sivers effect is introduced.

Relevance of Twist3Twist3 and Sivers effect Sivers effect is studied. PRL97, 082002 (2006)PRD73, 094017 (2006)

Available Probes at RHIC

1

pp+p+ph+Xh+X Both mix

2

pp+p+pdi-jet+Xdi-jet+X Sivers?Sivers?

3 p+ph+h+X (far side) Separate?

4

p+ph+h+X (near side)

p+pjet+X

Collins

Sivers

5

p+pdirect +X Sivers

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p+pl+l (Drell-Yan) Sivers

Collins function: analyzer of “Transversity”

Transversity: ,xq,xq,xq

: Probability to observe parton whose pol. vector is “with” or “against” the proton pol. vector with the renormalization scale .

,xq

q(x,) has not been measured experimentally.

Lattice QCD calculates the first moments of q(x,) for u,d, s quarks and the sum at 2=2 GeV2.

,xq,xqdxq1

0

sdu

“with”

“against”

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Relative LuminosityRelative Luminosity

Use BBCs at Use BBCs at 1.5 m from the interaction point 1.5 m from the interaction point to measure bunch-by-bunch luminosityto measure bunch-by-bunch luminosityo LLii=N=Nii/(/(Efficiency) , Efficiency) , Eff.=const.=22.9mbEff.=const.=22.9mb9.7%9.7%

Use independent measurement from ZDCs Use independent measurement from ZDCs ((18m) to check for intrinsic luminosity 18m) to check for intrinsic luminosity asymmetryasymmetry

For Run 6 (200 GeV):For Run 6 (200 GeV): AALLLL(BBC-ZDC)=3.8(BBC-ZDC)=3.81.6*101.6*10-4-4 (>2 standard (>2 standard

deviations) deviations) AALLLL=5.4*10=5.4*10-4 -4

o Sizeable asymmetry compared to stat. error of low pSizeable asymmetry compared to stat. error of low pTT datadata

o Can be instrumental or physics effect Can be instrumental or physics effect need to find need to find outout

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PHENIX: 0 mid-rapidity, 200GeVhep-ex-0704.3599PHENIX: hep-ex-0704.3599

00 cross section and soft cross section and soft PhysicsPhysics

Exponent (eExponent (e--pTpT) ) describes pion cross describes pion cross section at psection at pTT<<1 1 GeV/c (dominated by GeV/c (dominated by soft physics): soft physics): =5.56=5.560.02 0.02

(GeV/c)(GeV/c)-1-1

22/NDF=6.2/3/NDF=6.2/3Assume that Assume that

exponent describes exponent describes soft physics soft physics contribution also at contribution also at higher phigher pTT soft soft physics contribution physics contribution at pat pTT>2 GeV/c is >2 GeV/c is <10%<10%