Transverse Spin Physics at RHIC

M. Grosse Perdekamp (University of Illinois and RBRC)

International Workshop on Semi-Inclusive

Reactions and 3D-Parton Distributions

May 18-20, 2005

Jefferson Lab, Newport News, Virginia, USA

Transverse Spin Physics at RHIC 2 May 18

Transverse Spin Physics at RHIC

o Motivation Measurement of the Sivers function Extract transversity distributions from QCD analysis: SIDIS + pp + e+e-

o Polarized p-p at RHIC Polarized collider + experiments Does NLO pQCD provide stable framework for the extraction of polarized PDFs?

o Transverse Spin Physics AN Sivers, transversity/Collins, sub-leading

twist back-to-back correlations in Jets Sivers AT (Collins, IFF) Transversity/Collins AT (Drell Yan) Sivers ATT (Drell Yan) Transversity

o Summary

Transverse Spin Physics at RHIC 3 May 18

Motivation: Global Transversity Analysis

LIC-RHIC/e-e JLAB,

COMPASS, S, HERME

IFF versity trans

Collins versity trans

SIDIS

GSI STAR, PHENIX,S, BRAHM

ity transversersity transv

: Yan DrellA

IFF ersity transv

Collins sity transver:Jets in A

Jets in A hadrons, inclusivefor A

pp

TT

T

TTN

TransversityTensor Charge

)(RBRC/UIUC BELLE

FFceInterferen

FFCollins ee -

BLT sum rule and Lattice QCD

Factorization and Universality?

Does pQCD provide a stable frame work for a global transversity analysis?

RBRC workshop September 2000

Transverse Spin Physics at RHIC 4 May 18

Collins FF (and IFF): e+e- hadrons (see Akio Ogawa’s talk)

1hP

2hP

2cm

21

111

121T

221

21

4

1y1yyB

zHzHyBddzdzd

Xhheedσ

sin

cos q

2-hadron inclusive transverse momentum dependent cross section:

e+e- CMS frame:

e-

e+

Transverse Spin Physics at RHIC May 18

AGSLINACBOOSTER

Polarized Source

Spin RotatorsPartial Snake

Siberian Snakes

200 MeV Polarimeter

AGS Internal Polarimeter

Rf Dipole

RHIC pC Polarimeters Absolute Polarimeter (H jet)

PHENIX

PHOBOS BRAHMS & PP2PP

STAR

Siberian Snakes

Run 041

s2

cm30

106~GeV 200

peakLs ,

Pb~45% , 55 bunches

Run 05

AGS pC Polarimeter

Polarized p-p at RHIC 2005: complete instrumentation!

Helical Partial SnakeStrong Snake

Spin Flipper

1s

2cm

31101~GeV 200

Ls ,

<Pb> = 45%

Commision strong snake

Transverse Spin Physics at RHIC 6 May 18

RHIC 2005: 200 GeV pp, ∫Ldt, May 17th

2.88 pb-1 live ZDCLL1

PHENIX Goal 5.5 pb-1 live BBCLL1

(5/17/05)

27.7 B BBCLL1 events sampled

1.23 pb-1 live BBCLL1

June 25, 2005(3.56 pb-1 projected)

Transverse Spin Physics at RHIC 7 May 18

(5/17/05)

PHENIX Goal 226 nb-1

60.2 nb-1

June 25, 2005(190 nb-1 projected)

RHIC 2005: 200 GeV pp, FoM, May 17th

Transverse Spin Physics at RHIC 8 May 18

GRSV standard ∆G(x)

Gluon distribution from NLO pQCD fit to DIS data on A1, Gluck Reya, Stratmann, Vogelsang Phys. Rev. D63:094005, 2001

ALL in inclusive π0 production (PHENIX)

ALL(π0)

∫Ldt=3pb-1

P=0.4

Vogelsang hep-ph/0405069

Input:∆G(x)=G(x)

GRSV: standard ∆G(x)

∆G(x)=0 ∆G(x)= -G(x)

ALL in inclusive jet production (STAR)Jager, Stratmann, Vogelsang hep-ph/0404057

ALL(Jets)

∫Ldt=3pb-1

P=0.4

Input:∆G(x)=G(x)

GRSV: standard ∆G(x)

∆G(x)= -G(x)

∆G(x)=0

pT [GeV/c] pT [GeV/c]

Expected in run 05: ∫Ldt =5pb-1 P =0.5All required instrumentation in STAR and PHENIX is in place!

Goals for 2005: (a) 1st look at the Gluon Polarization

(b) precision measurment of AN

Transverse Spin Physics at RHIC 9 May 18

Experiments with polarized protons at RHIC

polarization measurements

STARSTAR 75% longitudinal, 25% transverse

ALL (hadrons, jets, direct photons) AL (W-bosons) AN (hadrons, jets), AT (Drell Yan, Collins, IFF) ATT (Jets, Drell Yan)

PHENIXPHENIX 75% longitudinal, 25% transverse

BRAHMSBRAHMS 100% transverse AN (identified charged hadrons)

PHOBOS, pp2pp no “active” spin program

Transverse Spin Physics at RHIC 10

May 18

Does pQCD provide a stable for the extraction of PDFs at NLO from RHIC data?

o Good agreement between NLO pQCD calculations and experiment can use a NLO pQCD analysis to extract spin dependent quark and gluon distributions from RHIC data!

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

gluon fragmentation !?

Transverse Spin Physics at RHIC 11

May 18

• NLO-pQCD calculation– Private communication with

W.Vogelsang– CTEQ6M PDF.– direct photon + fragmentation photon– Set Renormalization scale and factorization scale pT/2,pT,2pT

Direct Photons: NLO pQCD vs RHIC data

Scale dependence ofCross sections in NLOpQCD calculations

Transverse Spin Physics at RHIC 12

May 18

E704: AN

The observed asymmetries could result from

Transversity x Spin-dep.fragmentation (Collins-Heppelmann effect),

or Sivers effect or Higher-twist effects

Sterman and Qiu Initial State Twist 3 Koike Final State Twist

or a combination of the above

leftright

•Fermilab E-704 reported large

asymmetries AN in pion productions

GeV 4.19at sXpp

E704

PT=0.5~2 GeV/c

�0 – E704, PLB261 (1991) 201.�π+/- - E704, PLB264 (1991) 462.

Transverse Spin Physics at RHIC 13

May 18

Transverse Spin Physics at RHIC, first Results: AN

o Experiments are ready for spin measurements at low luminosity relative luminosity ~ 5x10-4 trigger polarization analysis data analysis

PHENIX AN(π0) and AN(π0) at |η|<0.35

C. Aidala, DIS 2004, to be published

STAR AN(π0) at 3.4<η<4.0 Phys.Rev.Lett.92:171801,2004

Run 02, ∫Ldt ~ 0.2pb-1, P~0.15

o First spin results from RHIC AN sizeable in forward XF

AN compatible with 0 at η~0

Transverse Spin Physics at RHIC 14

May 18

Run 3 preliminary backward angle data no significant asymmetry (hep-ex/0502040)

STAR: AN for backward angles from 2003 data

Transverse Spin Physics at RHIC 15

May 18

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 From the ongoing 2005 run the statistical errors will be reduced by a factor 6-7

o New absolute RHIC polarimeter will reduce the systematic error by a factor 4

What can be learned from confronting model calculations with precision data on AN?

Transverse Spin Physics at RHIC 16

May 18

AN for Protons from BRAHMS

BRAHMS preliminary

Proton AN is compatible with 0AN will be available for pions, kaons and protons from run 2005

What do we learn from comparing AN for different fragmentation functions?

Transverse Spin Physics at RHIC 17

May 18

Future: RHIC Spin Longitudinal vs Transverse Running

2004 2005 2006 2007 2008 2009 ….

pp 5+0 5+10 5+11 0 5+9 156pb-1

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

P= 0.45 0.5 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= 6x1030cm-2s-1 8x1031cm-2s-1

Transverse Spin Physics at RHIC 18

May 18

(A) Transverse Spin Physics Channels at RHIC for “Low” Luminosity

GeV 200,pb 101 1 sLdt

)( :A Measure N XhppAN STAR Phys. Rev. Lett. 92:171801, 2004

Boer and Vogelsang (hep-ph/0312320):azimuthal back to back correlation between hadrons in opposite hemisphere jets:

Separation of intrinsic transverse quark spin (transversity) from trans-verse momentum effects (Sivers)?

Clean channel for Sivers effect!

STAR, PHENIX and BRAHMS STAR and PHENIX

(I) (II)

Transverse Spin Physics at RHIC 19

May 18

Sensitivity Check for Back-to-Back Sivers Asymmetry (based on 2003 pp

sample)Full di-jet SiversReduced by lower <P>, di-hadron smearingRun03 p+p gamma-charged, 0.35/pb

•Given 0.35/pb of data, we should be able to get 1% statistical significance in AN using gamma-charged measurements of jet dphi•Expected raw AN could be 3.5%

•Could also be as low as 0.5%, or as large as 10%•x-dependence of Sivers?

•Effects from P=0.5, jet angle not aligned with transverse polarization, and fragmentation reduces raw AN to ~1.0%•Have not evaluated systematic errors yet (underlying event…)

Transverse Spin Physics at RHIC 20

May 18

XppAT

),(

,

:ionFragmentat ceInterferen

)(

: Jets in EffectCollins

XJetppAT J.C. Collins, Nucl. Phys. B396, 161(1993)

R. Jaffe, X.Jin, J. Tang Phys. Rev. D57 (1999)5920

J. Collins, S. Heppelmann, G. Ladinsky, Nucl.Phys. B420 (1994)565

GeV 200,pb 100-03 1 sLdt

Statistical sensitivity for AT with 32pb-1

STAR and PHENIX

(B) Transverse Spin Physics Channels at RHIC for “High” Luminosity

STAR and PHENIX

34 103105 TTA

production jet Inclusive

W. Vogelsang and M. Stratmann, RBRC Wrkshp on Transversity (2000)

Transverse Spin Physics at RHIC 21

May 18

qqllppATT )( : YanDrell

ionFragmentat ceInterferen Jets, in Collins

: Photon Direct

EIC

J.Ralston and D.E. Soper, Nucl. Phys. B152, 109(1979)

RHIC-e ,fb8 1 Ldt

RH

IC I

I

ionFragmentat ceInterferen

Jets in Effect Collins

(C) Transverse Spin Physics Channels at RHIC II and e-RHIC

Drell Yan8fb-1, large acceptance detector for Drell Yan

]GeV[ masspair lepton

Transverse Spin Physics at RHIC 22

May 18

Collins Effect in SIDIS at e-RHIC 2.01.0 z

7.05.0 z5.03.0 z

0.17.0 z

3.02.0 zAProjected errors on A in 5 z- bins

day) 1 (

Luminosity Integrated

AcceptanceDetector

120

6.36.3

pb

1.0

0

1 22

z

Q

x

GeV :Cuts

F

A A

A

A

x x

x

x x

)( XelpAT

Transverse Spin Physics at RHIC 23

May 18

Summaryo All instrumentation for polarized proton collisions has been installed: Unique tool to study proton structure! o First results on AN

2005 precision measurements comparisons between pions, kaons and protons

o Broad program with transverse spin with increasing luminosity:

AN in inclusive hadrons and jet production Sivers type back-to-back correlation between jets AT for Collins and IFF analysis

AT and ATT for Drell Yan

o Supporting effort to measure spin dependent fragmentation functions at Belle (RBRC/UIUC)