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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)