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RHIC Spin Physics. M. Grosse Perdekamp University of Illinois and RBRC. STAR. Physics goals Experimental tools Polarized proton-proton collisions at high energies Results and outlook Gluon Spin Transverse spin physics W-physics and upgrades.

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RHIC Spin Physics

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rhic spin physics

RHIC Spin Physics

M. Grosse Perdekamp

University of Illinois and RBRC


  • Physics goals
  • Experimental tools
  • Polarized proton-proton collisions at high energies
  • Results and outlook
  • Gluon Spin
  • Transverse spin physics
  • W-physics and upgrades

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

rhic five complementary experiments
RHIC  five complementary experiments

RHIC: ion-ion and polarized p-p Collider


RHIC Spin Overview

physics at the r elativistic h eavy i on c ollider
Physics at the Relativistic Heavy Ion Collider
  • Quark Matter at high Temperatures and Densities
  • ion-ion collisions (Cu-Cu, Au-Au: √sNN=22.5, 62, 130, 200 GeV)
  • Proton Spin Structure
  • polarized proton-proton collisions (p-p: √s=200 to 500 GeV)
  • Low-x and high parton densities
  • ion-deuteron collisions (d-Au: √sNN=200 GeV)

C. Cagliardi

low-x: Sat.11.10

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

RHIC Spin Overview


Proton Spin Structure in Polarized

p-p Collisions at RHIC


determine first moment of

the spin dependent gluon


flavor separation of quark

and anti-quark spin


measurement of trans-

versity and Sivers


available channels

jets, hadrons, photons,

photon-jet, heavy flavor

Single spin lepton asym-

metries in W-production

(1) AN

(2) ATT in Collins- and


(3) ATT and AT In Drell Yan

RHIC Spin Overview


Access to Parton Distributions at RHIC

Measure: (spin dependent) cross sections

QCD analysis: (spin dependent) distribution functions

RHIC Spin Overview

example d g x from a global nlo pqcd analysis with projected future direct photon data from phenix
Example: DG(x) from a global NLO pQCD analysis with projected future direct photon data from PHENIX

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

QCD analysis

of inclusive

DIS data

QCD analysis

DIS data + future

direct photons

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

RHIC Spin Overview

inclusive hadron cross sections vs nlo qcd
Inclusive Hadron Cross Sections vs NLO QCD

PHENIX π0 cross section a |η|<0.35


STAR π0 cross section a 3.4<η<4.0


RHIC Spin Overview


Direct Photons and Inclusive Jets vs NLO pQCD

Direct Photon Cross section

Inclusive Jet Cross section

M.Miller, hadronic final states: Sat.14.20

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!

Theory calculation show good

agreement with the experimental

cross section.

STAR Preliminary

M. Stratmann,

spin: Fr 16:30

Theory perspective:

RHIC Spin Overview


Last Week at RHIC

peak average  design

L 2.5 1.2 6.0

P 67% 61% 70%

Luminosity in 1031cm-2s-1

A novel experimental method: Probing Proton Spin Structure

Through High Energy Polarized p-p Collisions

RHIC pC Polarimeters

Absolute Polarimeter (H jet)

Siberian Snakes

A. Bravar,

spin: Fr 16:10



2005 Complete!

high current polarized source

high energy proton polarimetry

helical dipoles magnets

Siberian Snakes

Spin Flipper



Spin Rotators

Partial Snake

Strong Snake

Helical Partial Snake

Polarized Source




200 MeV Polarimeter

Generous support from

RIKEN, Japan and DOE

Rf Dipole

AGS Polarimeter

RHIC Spin Overview


Polarized p-p at RHIC: Detector Instrumentation

  • Upgrades to adapt “heavy ion detectors” for high rate p-p
  • environment (eg. PHENIX trigger, STAR EMC,
  • STAR tracking at high momentum)
  • Local polarimeters to verify polarization direction at the
  • interaction point (important for longitudinal spin!)
  • Relative luminosity: arises in calculating asymmetries
  • between yields from different bunch crossings, say i and j eg.

F. Simon,

spin: Sa10:20

RHIC Spin Overview

brahms a n for charged k p
BRAHMS: AN for charged π,K, p

100% transverse spin!

Two spectrometer arms

with good particle ID at

high momenta

RHIC Spin Overview

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

EM Calorimeter



Time Expansion


Muon Tracking




Muon ID


Pad Chambers



North Muon


Drift Chambers

South Muon


Time of Flight


Four spectrometer arms

with excellent trigger and

DAQ capabilities.

Ring Imaging


RHIC Spin Overview

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

Large acceptance TPC

and EMC -1<η<2

RHIC Spin Overview

rhic detector status and upgrades
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.

RHIC Spin Overview


Gluon Spin Distribution

ALL in inclusive Jets (STAR)

ALL for inclusive π0 (PHENIX)


ALL from Inclusive Jets in p+p

Collisions at √s=200GeV

jet cone=0.4

STAR Preliminary

STAR Projections for 2006

*) Predictions:

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

J. Kiryluk,

spin: Sa 9:00

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

RHIC Spin Overview

run 5 a ll p 0 first constraints for g x
Run 5 ALL(p0): First constraints for ∆G(x)

Comparision with ∆G from QCD analysis of

DIS data: M. Glück, E. Reya, M. Stratmann, and

W. Vogelsang, Phys. Rev. D 53 (1996) 4775.

M. Liu,

spin: Sa 9:20

Y. Fukao,

spin: Sa 9:40

max ∆G from DIS

Excludes large gluon spin


Needs to be quantified

with NLO pQCD analysis!

standard ∆G from DIS

min ∆G possible

∆G =0

40% scale error (missing abso-

lute polarization measurement).


RHIC Spin Overview

nlo qcd analysis of dis a 1 a ll 0
NLO QCD Analysis of DIS A1 + ALL(π0)

M. Hirai, S. Kumano, N. Saito, hep-ph/0603212

(Asymmetry Analysis Collaboration)

M. Hirai,

spin: Sa 12:10

DIS A1 + ALL(π0)



RHIC Spin Overview


NLO QCD Analysis vs

High pT Hadron Production in DIS

High pT hadron production provides additional

constraints to fit for 0.07 < x < 0.3, high pT data

consistent with the three fit results for ΔG/G

DIS A1 + ALL(π0)


DIS A1 + ALL(π0) + neg ΔGinitial

RHIC Spin Overview


∆G Measurements by 2012

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

s=200 GeV incl. 0 prod’n

s=500 GeV incl. jet prod’n

  • 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

RHIC Spin Overview


Transverse Spin

AN for inclusive hadrons


C. Cagliardi,

spin: Fr14:20

K. Tanida,

spin: Fr14:40

J.H. Lee,

spin: Fr15:00


QCD Cross Sections for Transverse Spin

QCD: Asymmetries for transverse spin are small at

high energies (Kane, Pumplin, Repko, PRL 41, 1689–1692 (1978) )


(E704, Fermi National Laboratory):


QCD Test !



Suggestions: Sivers-, Collins-,

Qui-Sterman, Koike mechanisms !?

Can QCD be re-conciled with

large transverse asymmetries?

RHIC Spin Overview


STAR: AN for backward angles from 2003 data

PHENIX AN(π0) and AN(π0)at |η|<0.35


STAR AN(π0) at 3.4<η<4.0


and (hep-ex/0502040)

K. Tanida,

spin: Fr14:40

C. Cagliardi,

spin: Fr14:20


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

RHIC Spin Overview

brahms a n for charged pions
BRAHMS: AN for charged pions

J.H. Lee,

spin: Fr15:00

AN for pions:

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

pT vs XF

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

in 0.17 < xF < 0.32

xF x 100

  • 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)?

xF x 100

RHIC Spin Overview


Large AN: mainly two mechanisms

M. Anselmino, M. Boglione, U. D’Alesio, E. Leader,

S. Melis and F. Murgia hep-ph/0601205

(I) Sivers quark and gluon distributions

Correlation between proton-spin and

transverse quark momentum


(II) Transversity quark-distributions

and Collins fragmentation

Correlation between proton- und quark-spin

and spin dependent fragmentation


x Collins


RHIC Spin Overview


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

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

Current measurements should be sensitive at the level of predictions

D. Boer and W. Vogelsang,

Phys.Rev. D 69 (2004) 094025

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

RHIC Spin Overview

measurement of transverse parton distributions at rhic
Measurement of Transverse Parton Distributions at RHIC

luminosity sufficient?

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


RHIC by 2009 at 200 GeV

∫Ldt ~275pb-1delivered

∫Ldt ~100pb-1 accepted

(eg. PHENIX: vertex cut,

trigger efficiencies, duty


 ∫Ldt ~25 pb-1 transverse


RHIC Spin Overview

collins function measurement in e e at belle
Collins Function Measurement in e+e- at Belle

e+e- CMS frame:

R. Seidl,

spin: Th 17:30








2-hadron inclusive transverse momentum dependent cross section:

RHIC Spin Overview


LO-QCD Analysis of HERMES and

Belle Results (Efremov, Goeke, Schweitzer, hep-ph/0603054)



Combined fit to Hermes asymmetries (Transversity x Collins-FF) and Belle asymmetries (Collins-FF2)  Excellent agreement!

RHIC Spin Overview


Plans for the measurement

of spin dependent quark and

anti-quark in W-production



Projected Sensitivities in PHENIX

  • 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 GeV

is projected to yield ∫Ldt ~950pb-1

RHIC Spin Overview



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 high

Statistics polarized took place in 2005. Run 2006

consists of 16 weeks for proton-running.

Polarized Protons at RHIC provide a powerful

experimental tool to study the structure of the

nucleon. We are at the beginning of a broad new

program on nucleon substructure.

RHIC Spin Overview

physics vs luminosity and polarization at rhic
Physics vs Luminosity and Polarization at RHIC

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

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

P= 0.5 0.6 0.7 ……………………………………

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

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

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

@ 200GeV

@ 500GeV

Inclusive hadrons + Jets

~ 25% Transverse Physics

Charm Physics

direct photons

bottom physics


ALL(hadrons, Jets)




RHIC Spin Overview

carbon cni polarimeter in the ags polarization during acceleration
Carbon CNI Polarimeter in the AGS: Polarization during Acceleration

each point = 50 MeV step

raw asymmetry = AN· PB

intrinsic: Gg =

imperfection: Gg = n



Gg = 1.91 Ebeam



red line: simulation of polarization

losses assuming constant AN

RHIC Spin Overview


Run 04+05: The Polarized Jet Target for RHIC

Courtesy Sandro Bravar,

and Yousef Makdisi

  • Polarized Hydrogen Gas Jet Target
  • thickness of > 1012p/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

RHIC Spin Overview

jet profile and tof vs energy
Jet Profile and TOF vs Energy

JET Profile: measured selecting pp

elastic events

recoil protons

elastic pp pp


FWHM ~ 6 mm

as designed

D ToF < ± 8 ns


118 cts. subtracted

Number of elastic pp events

T Kin [MeV]

CNI peak AN

1 < EREC < 2 MeV

 source


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

prompt events

and beam-gas

  • recoil protons unambiguously identified !

ToF vs EREC correlation

Tkin= ½ MR(dist/ToF)2

RHIC Spin Overview

bunch shuffle
Bunch shuffle

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

  • Randomly reassign helicity for each fill and recalculate asymmetry.
  • Do 1000 times and look at c2 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

RHIC Spin Overview

run5 p 0 cross section
Run5 p0 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.

2005 preliminary

p0 cross section

vs perturbative QCD

(W. Vogelsang)

(Data – Theory)/Theory

RHIC Spin Overview