RHIC Spin Physics M. Grosse Perdekamp University of Illinois and RBRC

International Workshop on Deep Inelastic Scattering, April 20-24, 2006 ,Tsukuba, Japan

o Physics goals

o Experimental tools

Polarized proton-proton collisions at high energies

o Results and outlook

Gluon Spin Transverse spin physics W-physics and upgrades

STARSTAR

RHIC Spin Overview 2 April 20th

RHIC five complementary experiments

RHIC: ion-ion and polarized p-p Collider

pp2pppp2pp

RHIC Spin Overview 3 April 20th

Physics at the Relativistic Heavy Ion Collider

o Quark Matter at high Temperatures and Densities

ion-ion collisions (Cu-Cu, Au-Au: √sNN=22.5, 62, 130, 200 GeV)

o Proton Spin Structure

polarized proton-proton collisions (p-p: √s=200 to 500 GeV)

o Low-x and high parton densities

ion-deuteron collisions (d-Au: √sNN=200 GeV)

C. Cagliardilow-x: Sat.11.10

very active field: eg. 74 PRL letters in the first 5 years

RHIC Spin Overview 4 April 20th

available channels

jets, hadrons, photons, photon-jet, heavy flavor

Single spin lepton asym-metries in W-production

(1) AN

(2) ATT in Collins- and Interference-Fragmentation(3) ATT and AT In Drell Yan

goals

determine first moment ofthe spin dependent gluondistribution.

flavor separation of quarkand anti-quark spin distributions

measurement of trans-versity and Sivers distributions

Proton Spin Structure in Polarized p-p Collisions at RHIC

qTfq

1,

qq ,

G

RHIC Spin Overview 5 April 20th

Access to Parton Distributions at RHIC

)(),(),(),( xGxqxGxqdp

d

T

Measure: (spin dependent) cross sections

QCD analysis: (spin dependent) distribution functions

RHIC Spin Overview 6 April 20th

Example:G(x) from a global NLO pQCD analysis with projected future direct photon data from

PHENIX

M. Hirai, H.Kobayashi, M. Miyama et al. (Asymmetry Analysis Collaboration)

Does NLO pQCD provide a reliable framework for the interpretation of polarized proton data in terms of

polarized parton distribution functions?

QCD analysisof inclusiveDIS data

QCD analysisDIS data + futuredirect photons

RHIC Spin Overview 7 April 20th

Inclusive Hadron Cross Sections vs NLO QCD

PHENIX π0 cross section a |η|<0.35 Phys.Rev.Lett.91:241803,2003

STAR π0 cross section a 3.4<η<4.0 Phys.Rev.Lett.92:171801,2004

RHIC Spin Overview 8 April 20th

Theory calculation show good agreement with the experimentalcross section.

Direct Photons and Inclusive Jets vs NLO pQCD

M.Miller, hadronic final states: Sat.14.20

Inclusive Jet Cross sectionDirect Photon Cross section

STAR Preliminary

PHENIX Preliminary

Good agreement between NLO pQCD calculations and experiment at RHIC ! Use NLO pQCD analysis to extract (spin dependent) quark and gluon distributions from RHIC data!

M. Stratmann, spin: Fr 16:30

Theory perspective:

RHIC Spin Overview April 20th

AGSLINACBOOSTER

Polarized Source

Spin RotatorsPartial Snake

Siberian Snakes

200 MeV Polarimeter

AGS Polarimeter

Rf Dipole

RHIC pC Polarimeters Absolute Polarimeter (H jet)

PHENIX

PHOBOS BRAHMS & PP2PP

STAR

Siberian Snakes

Helical Partial Snake

Strong Snake

Spin Flipper

2005 Complete!2005 Complete!

A novel experimental methodA novel experimental method: Probing Proton Spin Structure Through High Energy Polarized p-p Collisions

high current polarized sourcehigh energy proton polarimetry helical dipoles magnets

Last Week at RHIC

peak average design

L 2.5 1.2 6.0

P 67% 61% 70%

Luminosity in 1031cm-2s-1

A. Bravar, spin: Fr 16:10

Generous support fromRIKEN, Japan and DOE

RHIC Spin Overview 10

April 20th

Polarized p-p at RHIC: Detector Instrumentation

(I) Upgrades to adapt “heavy ion detectors” for high rate p-p environment (eg. PHENIX trigger, STAR EMC, STAR tracking at high momentum)

(II)Local polarimeters to verify polarization direction at the interaction point (important for longitudinal spin!)

(III)Relative luminosity: arises in calculating asymmetries between yields from different bunch crossings, say i and j eg.

F. Simon, spin: Sa10:20

L

LR

jNR iN

jNR iN

PPA

ybLL ,

) crossing( )crossing(

) crossing( )crossing(1

RHIC Spin Overview 11

April 20th

100% transverse spin!Two spectrometer armswith good particle ID athigh momenta

BRAHMS: AN for charged π,K, p

RHIC Spin Overview 12

April 20th

PHENIX spin physics program: ∆G, ∆q/∆q, Sivers, δq

Muon IDPanels

CentralArms

North MuonArm

South MuonArm

Ring ImagingCerenkov

EM Calorimeter

Muon TrackingChambers

Beam-BeamCounter

Multiplicity/VertexDetector

Time ExpansionChamber

Drift Chambers

Pad Chambers

Time of FlightPanels

Four spectrometer arms with excellent trigger and DAQ capabilities.

RHIC Spin Overview 13

April 20th

STAR spin physics program: ∆G, ∆q/∆q, Sivers, δq

Large acceptance TPC and EMC -1<η<2

RHIC Spin Overview 14

April 20th

RHIC Detector Status and Upgrades

o All instrumentation is in place for the planned measurements on spin dependent gluon distributions and transverse spin.

o W-physics (flavor separation of quark and anti-quark polarizations) requires upgrades in PHENIX (muon trigger, funded by NSF and JSPS) and STAR (forward tracking, grant proposal to DOE in preparation).

o In PHENIX a central silicon tracking upgrade and a forward tungsten silicon calorimeter upgrade will significantly enhance capabilities for jet and photon-jet physics.

o A RHIC luminosity upgrade (RHIC II) for heavy ions with electron cooling will gain a factor 3-5 (beyond design) in luminosity from 2012.

Gluon Spin Distribution ALL in inclusive Jets (STAR) ALL for inclusive π0 (PHENIX)

RHIC Spin Overview 16

April 20th

Results limited by statistical precision Total systematic uncertainty ~0.01 (STAR) + beam pol. (RHIC) GRSV-max gluon polarization scenario disfavored

jet cone=0.4

*) Predictions: B.Jager et.al, Phys.Rev.D70(2004) 034010

ALL from Inclusive Jets in p+p Collisions at √s=200GeV

J. Kiryluk, spin: Sa 9:00

STAR Preliminary

4.0

4.0 1

P

pbLdt

STAR Projections for 2006

2006) (run 5.0

10 1

P

pbLdt

RHIC Spin Overview 17

April 20th

Run 5 ALL(): First constraints for ∆G(x)

Comparision with ∆G from QCD analysis ofDIS data: M. Glück, E. Reya, M. Stratmann, and W. Vogelsang, Phys. Rev. D 53 (1996) 4775.

¨

standard ∆G from DIS

∆G =0

max

∆G from

DIS

min ∆G possibleExcludes large gluon spincontributions!

Needs to be quantified with NLO pQCD analysis!

2005) (run 45.0

7.2 1

P

pbLdt

Y. Fukao, spin: Sa 9:40

40% scale error (missing abso-lute polarization measurement).

M. Liu, spin: Sa 9:20

RHIC Spin Overview 18

April 20th

NLO QCD Analysis of DIS A1 + ALL(π0)

M. Hirai, S. Kumano, N. Saito, hep-ph/0603212(Asymmetry Analysis Collaboration)

DIS A1 + ALL(π0)

ACC03

x

0.14 0.21 1.27 0.5 AAC03

10.0 0.25 1.08 0.47 A DIS

0.070.27 0.320.31 )(A DIS

)(

1

01

LLA

dxxG

M. Hirai, spin: Sa 12:10

RHIC Spin Overview 19

April 20th

NLO QCD Analysis vs High pT Hadron Production in DIS

DIS A1 + ALL(π0)

DIS A1

DIS A1 + ALL(π0) + neg ΔGinitial

High pT hadron production provides additionalconstraints to fit for 0.07 < x < 0.3, high pT dataconsistent with the three fit results for ΔG/G

RHIC Spin Overview 20

April 20th

Final results on ∆G will come from combined NLO analysis of all channels at RHIC and in DIS

RHIC measurements will span broad range in x with good precision. multiple channels with independent theo. and exp. uncertainties.

Uncertainty through extrapolation to small x

s=200 GeV incl. 0 prod’n s=500 GeV incl. jet prod’n

∆G Measurements by 2012 see Spin report to DOE http://spin.riken.bnl.gov/rsc/

Transverse Spin AN for inclusive hadrons (BRAHMS, PHENIX, STAR)

C. Cagliardi, spin: Fr14:20

K. Tanida, spin: Fr14:40

J.H. Lee, spin: Fr15:00

RHIC Spin Overview 22

April 20th

QCD Cross Sections for Transverse Spin

QCD: Asymmetries for transverse spin are small at high energies (Kane, Pumplin, Repko, PRL 41, 1689–1692 (1978) )

Xpp π+

π-

π0

LR

N

LR

PA

1 :Observable

GeV 20s

Suggestions: Sivers-, Collins-, Qui-Sterman, Koike mechanisms !?

Experiment (E704, Fermi National Laboratory):

4q 10,20,3m example, N

qN AGeVsMeV

s

mA

QCD Test !

Can QCD be re-conciled withlarge transverse asymmetries?

RHIC Spin Overview 23

April 20th

STAR: AN for backward angles from 2003 data

PHENIX AN(π0) and AN(π0) at |η|<0.35

Phys.Rev.Lett.95:202001,2005

STAR AN(π0) at 3.4<η<4.0Phys.Rev.Lett.92:171801,2004and (hep-ex/0502040)

C. Cagliardi, spin: Fr14:20

K. Tanida, spin: Fr14:40

update!

• Sizable asymmetries for xF > 0.4• Back angle data consistent with AN ~ 0• Updated results in parallel session!

RHIC Spin Overview 24

April 20th

BRAHMS: AN for charged pions

xF x 100

pT vs XF

xF x 100

AN for pions:

NN = -0.08 +- 0.005 +- [0.02] = -0.08 +- 0.005 +- [0.02]

in 0.17 < xin 0.17 < xFF < 0.32 < 0.32

NN = +0.05 +- 0.005 +- [0.015]= +0.05 +- 0.005 +- [0.015]

o Expect new results from run 2005 for pions but also kaons and protons.

What can be learned by analyzing precision RHIC data on AN for different kinematics and different final state hadrons (Collins effect for kaons, protons)?

J.H. Lee, spin: Fr15:00

RHIC Spin Overview 25

April 20th

Large AN: mainly two mechanisms

(II) Transversity quark-distributions and Collins fragmentation

Correlation between proton- und quark-spin and spin dependent fragmentation

),()( 221

kzHxq

(I) Sivers quark and gluon distributions Correlation between proton-spin and transverse quark momentum

),( 21 kxf qT

M. Anselmino, M. Boglione, U. D’Alesio, E. Leader, S. Melis and F. Murgia hep-ph/0601205

quar

k-Si

vers

gluon-Sivers

Transverstiy x Collins

RHIC Spin Overview 26

April 20th

D. Boer and W. Vogelsang,Phys.Rev. D 69 (2004) 094025

Back-to-back di-Jets: Access to Gluon Sivers Function

Current measurements should be sensitive at the level of predictions

Measurements near mid-rapidity with STAR – search for spin-dependent deviation from back-to-back alignment

> 7 GeV trigger jet> 4 GeV away side jet

PHENIX: measurement of back-to-back di-hadrons.

RHIC Spin Overview 27

April 20th

Measurement of Transverse Parton Distributions at RHIC

AN yes, very good

AN(back-to-back) good (Sivers signature!)

AT (Collins FF in jets) fair

AT (Interference FF) fair

ATT (Jets) systematics limited

AT (Drell Yan)

ATT( Drell Yan)

Direct photons (AN,AT(CFF, IFF))

RHIC by 2009 at 200 GeV

∫Ldt ~275pb-1 delivered

∫Ldt ~100pb-1 accepted(eg. PHENIX: vertex cut,trigger efficiencies, dutyfactor)

∫Ldt ~25 pb-1 transverse

RH

IC II

luminosity sufficient?

RHIC Spin Overview 28

April 20th

Collins Function Measurement in e+e- at Belle

1hP

2hP

)(cosq 2

111

11212

21

21 zHzHyBddzdzd

Xhheedσ

T

2-hadron inclusive transverse momentum dependent cross section:

e+e- CMS frame:

e-

e+

R. Seidl, spin: Th 17:30

RHIC Spin Overview 29

April 20th

LO-QCD Analysis of HERMES and Belle Results (Efremov, Goeke, Schweitzer, hep-ph/0603054)

BELLE PRELIMINARY HERMES PRELIMINARY

Combined fit to Hermes asymmetries (Transversity x Collins-

FF) and Belle asymmetries (Collins-FF2) Excellent agreement!

Plans for the measurement of spin dependent quark and anti-quark in W-production at RHIC

RHIC Spin Overview 31

April 20th

Projected Sensitivities in PHENIX

Machine and detector requirements:Machine and detector requirements:

– ∫Ldt=800pb-1, P=0.7 at √s=500 GeV

– required upgrades:

high rate muon trigger (PHENIX)

high momentum tracking (STAR)

2009 to 2012 running at √s=500 GeVis projected to yield ∫Ldt ~950pb-1

RHIC Spin Overview 32

April 20th

Summary

RHIC and it’s experiments are the world’s first facility capable of colliding high energy polarized protons (and heavy ions).

Collider and Experiments are complete and a first highStatistics polarized took place in 2005. Run 2006consists of 16 weeks for proton-running.

Polarized Protons at RHIC provide a powerful experimental tool to study the structure of thenucleon. We are at the beginning of a broad new program on nucleon substructure.

RHIC Spin Overview 33

April 20th

Physics vs Luminosity and Polarization at RHIC

2005 2006 2007 2008 2009 …. 2012 (RHIC II)

10 pb-1 …………………………………… 275pb-1 …….. 950pb-1

√s= ……………………….. 200 GeV …………………......... 500 GeV|

P= 0.5 0.6 0.7 ……………………………………

Inclusive hadrons + Jets ~ 25% Transverse Physics Charm Physics direct photons bottom physics W-physics

ALL(hadrons, Jets) ALL(charm)

ALL(γ) AL(W)

L= 1x1031cm-2s-1 6x1031cm-2s-1 1.6x1032cm-2s-1

see Spin report to DOE http://spin.riken.bnl.gov/rsc/

@ 200GeV @ 500GeV

RHIC Spin Overview 34

April 20th

Carbon CNI Polarimeter in the AGS: Polarization during Acceleration

raw

asy

mm

etry

= A

N

PB

12+ 36- 36+G = 1.91 Ebeamintrinsic: G =

imperfection: G = n

each point = 50 MeV step

48-

red line: simulation of polarization losses assuming constant AN

RHIC Spin Overview 35

April 20th

Run 04+05: The Polarized Jet Target for RHIC

Polarized Hydrogen Gas Jet Target

thickness of > 1012 p/cm2

polarization > 92.4% (+/-2)%!

no depolarization from beam wake fields

Silicon recoil spectrometer to measure

• The left-right asymmetry AN in pp elastic

scattering in the CNI region to AN < 10-3

accuracy.

• Transfer this to the beam polarization

• Calibrate the p-Carbon polarimeters

• 2004 analysis Pb = 0.39+/-0.03

Courtesy Sandro Bravar, and Yousef Makdisi

RHIC Spin Overview 36

April 20th

Jet Profile and TOF vs Energy

Hor. pos. of Jet 10000 cts. = 2.5 mm

Num

ber

of e

last

ic p

p ev

ents

FWHM ~ 6 mmas designed

• recoil protons unambiguously identified !

CNI peak AN

1 < E REC < 2 MeV prompt eventsand beam-gas

sourcecalibration

recoil protons elastic pp ppscattering

background118 cts. subtracted

JET Profile: measured selecting ppelastic events

ToF vs EREC correlation

Tkin= ½ MR(dist/ToF)2

ToF < 8 ns

T Kin [MeV]

RHIC Spin Overview 37

April 20th

Bunch shuffle• Randomly

reassign helicity for each fill and recalculate asymmetry.

• Do 1000 times and look at distribution.

• Agree with expected distribution

• Bunch to bunch systematics smaller than current statistics.

5<pT<6 GeV/c 6<pT<7 GeV/c 7<pT<8 GeV/c 8<pT<9 GeV/c

1<pT<2 GeV/c 2<pT<3 GeV/c 3<pT<4 GeV/c 4<pT<5 GeV/c

RHIC Spin Overview 38

April 20th

Run5 0 Cross Section

• Consistent with previous PHENIX results from runs 3+4

• Extends previous results to pT of 20 GeV/c.

• Theory is consistent with data over nine orders of magnitude.

preliminary0 cross section vs perturbative QCD (W. Vogelsang)

Data – Theory)/Theory