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PHENIX G: Results and Prospect

A.BazilevskyBNL

For the PHENIX Collaboration

RHIC Spin: Next DecadeBerkley, Nov 20-22, 2009

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G: Global Fit• Phys. Rev. Lett. 101, 072001(2008)• First truly global analysis of all available polarized data including RHIC

results

Uncertainty estimation:2=1 (optimistic)

2/2=2% (conservative)2/2=2%

Daniel de FlorianRodolfo SassotMarco StratmannWerner Vogelsang

Improved a lot after RHIC data have been included

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G: PHENIX Contribution 0 at s=62 GeV , ||<0.35

PRD 79, 012003 (2009)0 at s=200 GeV, ||<0.35

PRL 103, 012003 (2009)

Run 6Run 5+6

Twice larger data sample collected in Run-2009Data analysis ongoing

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G: PHENIX Contribution (not yet included in global fit)

• Analysis similar to 0

• Different flavor structure• Independent probe of G

±

• Preferred fragmentation u+ and d- ;

u>0 and d<0 different qg contributions for +, 0, -

access sign of G

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G: PHENIX Contribution (not yet included in global fit)

Heavy Flavor• Production dominated by gluon

gluon fusion• Measured via e+e-, -, e, eX,

X• Need more P2L

Direct Photon• Quark gluon scattering dominates• Direct sensitivity to size and sign

of G• Need more P2L

~80%

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G: PHENIX Contribution 0 at s=200 GeV

Need to Extend x-rangeConstrain x

pT=2-12 GeV/c xg=0.02-0.3

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G: Path Forward

Improve precision of current measurements

Extend x-rangeChange s

Move to forward rapidities

Constrain kinematics (xg)More exclusive channels

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Incl. 0 s=200 GeV ~0Based on real efficiencies and yields from PHENIX data (Run6)

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Incl. 0 s=500 GeV ~0

Adds the lowest xT (xg) point – no competition for other points

Based on real efficiencies and yields from PHENIX data (Run9)

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Incl. 0 s=62 GeV ~0

Considerably better sensitivity at higher xT (xg) compared to s=200 GeV

Based on real efficiencies and yields from PHENIX data (Run6)

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s=62 – 500 GeV

s: 200 GeV 62 GeV: xg (peak): 0.15 0.25

s=62 GeV also provides essentially better sensitivity for xg>0.08

s: 200 GeV 500 GeV: xg (peak): 0.03 0.01

pT=2-2.5 GeV/c

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Forward Calorimetry

FOCAL: Tungsten absorber with silicon pad readout

1< <32 azimuth24 X0 deep

Available by 2013 (?)

Muon Piston Calorimeter (MPC): PbWO4

3.1 < || < 3.72 azimuthFully available from 2008

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MPC: 0 at s=500 GeV3.1 < || < 3.7

GS-C

PhythiaPYTHIALower-x parton

Log10(x)

GS-C

DSSV

Very good sensitivity to G at lower x (<0.01) even in limited data sampleAsymmetries are low need of spin flipper to reduce syst. uncertainties

25/pb, P=0.5

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FOCAL: direct at s=500 GeV

GS-CGS-BGS-A

ALL

pT (GeV)

300 pb-1 @ 500 GeV70% PolPythia 6.1

PISA• Isolation Cut, Photon ID Cuts• No Background

Reconstructed ALL, PISA

Even direct photons may give reasonable sensitivity at lower x … but only with full luminosity and high beam polarization

q

g

q jet

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Silicon Vertex tracker (VTX & FVTX)

FVTX endcaps1.2<||<2.7 mini strips

VTX barrel ||<1.2Available in 2011/12

432

eespx T

431

eespx T

FOCAL: pT and photon VTX: jet

May be luminosity (and polarization) hungry

Rejects hadronic backgroundc/b separated measurements

g

g Q

QQ = c or b

q

g

q jet

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Summary

PHENIX 0 (along with STAR incl. jet) ALL data from Run-2005/6 at s=200 GeV have made major contribution to G constraint in the xg range 0.02-0.3

Collected Run-2009 data sample at s=200 GeV is about twice larger than Run-2006; analysis is ongoing

Lower s (e.g. 62 GeV) will considerably improve G constraint for xg>0.1

Higher s (e.g. 500 GeV) + forward rapidity measurements give good sensitivity for xg<0.01

low asymmetries need of spin flipper

Many other channels (, ,,,e), each of them having smaller sensitivities to G than 0, altogether will give constraint similar to 0 should be included in global fit

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Backup

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Lower x parton

Higher x parton

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ALL with VTXHeavy flavor measurement Gamma - jet correlation

GeVs 5001300 pbLIntegrated Luminosity

Center of mass energy

charmbottom

L = 300 pb -1

P = 0.7

ALL distribution as function of pT

Simulation

200m < DCA

include backgrounds pT (GeV/c)

g = g

g = -g

GRSV_std

PYTHIA Simulation

ALL distribution as function of xg

GeVs 5001300 pbLIntegrated Luminosity

Center of mass energy

no backgroundsxg

L = 300 pb -1

P = 0.7

Simulation

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Heavy Flavor

1.12ˆ

Ms

1.5

2

5

g

g Q

QQ = c or b

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From soft to hard

exponential fit

Exponent (e-pT) describes our pion cross section data perfectly well at pT<1 GeV/c (dominated by soft physics):

=5.560.02 (GeV/c)-1

2/NDF=6.2/3

Assume that exponent describes soft physics contribution also at higher pTs soft physics contribution at pT>2 GeV/c is <10%

PRD76, 051106 (2007)

pT>2 GeV/c – hard scale?

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From soft to hard

xT scaling:

)(13

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Tn xGsdp

dE

Running (Q2)Evolution of PDF and FFHigher order effectsEtc.

n=n(xT,s)

Soft region: n(xT) increase with xT If ~exp(-pT)

Hard region: n(xT) decrease with xT

Stronger scale breaking at lower pT

2 GeV/c at s=62 GeV pT~2 GeV/c – transition from soft to hard scale?

2004.62log

log 4.62200 n

PRD76, 051106 (2007)

xT10-2 10-1