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Transcript of Nucleon Spin Structure 30 Years of Experiment: What have we learned? M. Grosse Perdekamp, University...
Nucleon Spin Structure
30 Years of Experiment: What have we learned?
M. Grosse Perdekamp, University of Illinois and RBRC
Nucleon Spin Structure 2 June 6 th
Overviewo Scientific Motivation and Early Beginnings
The Rabi School of Physics The SLAC – Bielefeld -- Tsukuba – Yale Collaboration Modern Experiments
o Nucleon Helicity Structure Quark spin ΔΣ Gluon spin ΔG Orbital angular momentum Lz GPDs !
o Transverse Spin
Transverse spin in hard scattering QCD Transversity and Collins Quark Fragmentation The Sivers Effect
Nucleon Spin Structure 3 June 6 th
ondistributiquark dependent spin
(x)q - (x) qq(x)
ondistributi momentumquark )( xq
ondistributi gluondependent spin
(x)G - (x) GG(x)
proton
quark
p
px
Scientific Motivation: Proton Structure Including Spin Degrees of Freedom
Constituents: quarks = u, d, s and gluons
(x)
:SpinQuark Total
,
1
0
x
x
q
(x)
:SpinGluon Total 1
0
x
x
GG
Nucleon Spin Structure 4 June 6 th
Proton Spin Structure from Inclusive Deep Inelastic Lepton-Nucleon
Scattering
electron or
muon probe
spin
proton target
spin
Qdxxq
xqxqxqQxg
,
21
0
21
0at )(
)()()(),(Extract spin dependent quarkdistribution functions from thespin structure function g1(x,Q2)
Large Q2: measure photon-quark absorption cross section doublespin asymmetry
),( 211 QxgAA
qqqLL
Nucleon Spin Structure 5 June 6 th
The Rabi School of Physics N. F. Ramsey, Eur. J. Phys. 11 (1990) 137J. Rigden, Physics World, Nov. 1999
(I) Molecular beam laboratory at Columbia University with strong emphasize on the development of new experimental technology.
(II) Field new, precise instrumentation to study fundamental questions of physics.
Example: Precision Measurements of “Hydrogen Spin Structure”
g-2 of the electron, P. Kusch Lamb shift, W. E. Lamb
Dirac Theory QED Tomonaga, Schwinger, Feynman
Nobel Prize 1955
Rabi, Nobel Prize 1944
Nobel Prize 1965
Nucleon Spin Structure 6 June 6 th
SLAC: Quark Structure of the Proton
Nucleon Quantum Chromo
Dynamics
Experiment: Deep inelastic electron nucleon scattering
Theory: quark structure of hadrons, QCD
Friedman,Kendall, TaylorNobel Prize 1990
Gell MannNobel Prize 1969
also Nakano, Nishijima
New instrumental method & fundamental physics !
Nucleon Spin Structure 7 June 6 th
Polarized Deep Inelastic Scattering
(I) Molecular beam technology as starting point for the development of polarized electron beams at Yale starting 1959.
(II)Physics:
(a) Proton spin structure (b) Test the Bjorken sum rule as fundamental QCD prediction
Experiments E80+E130 at SLAC
Bielefeld – CUNY – SLAC – Nagoya – Tsukuba – Yale (Coward, Kondo, Hughes)
EMC experiment at CERN (Gabathuler, Sloan, Hughes)
Vernon W. Hughes
a contribution from the Rabi School of Physics !
Nucleon Spin Structure 8 June 6 th
The Quark Spin Contribution ΔΣ
Quark Spin Contribution to the Proton Spin.
SLAC: 0.10 < xSLAC <0.7 CERN: 0.01 < xCERN <0.5
0.1 < xSLAC < 0.7A1(x)
x-Bjorken
EMC, Phys.Lett.B206:364,19881338 citations in SPIRES
1.005.007.0 CERNSLAC
0.01 < xCERN < 0.5“Proton Spin Crisis”
First Thesis on Nucleon SpinStructure E80/Yale, 1977:Noboru Sasao
Nucleon Spin Structure 9 June 6 th
DIS
Nucleon Spin Structure: 30 Years of Experiment
2000
ongoing
1995
2007
ongoing
ongoing
polarized pp
semi inclusive + exclusive processes, luminosity
Quark Spin – Gluon Spin – Transverse Spin – GPDs – Lz
SLAC E80-E155
CERN EMC,SMC COMPASS
FNAL E704
DESY HERMES
JLAB Halls A, B, C
RHIC BRAHMS, PHENIX, STAR
polarized proton beams, polarized proton collider
major experimental innovations
Nucleon Spin Structure June 6 th
AGSLINACBOOSTER
Polarized Source
Spin RotatorsPartial Snake
Siberian Snakes
200 MeV Polarimeter
Rf Dipole
RHIC pC Polarimeters Absolute Polarimeter (H jet)
PHENIX
PHOBOS BRAHMS & PP2PP
STAR
Siberian Snakes
AGS pC Polarimeter
Helical Partial Snake
Strong Snake
Spin Flipper
RHIC Spin InstrumentationRHIC Spin InstrumentationDevelopment 1995-2005Development 1995-2005
A novel experimental method: Probing Proton Spin Structure in High Energy Polarized Proton Collisions
Instrumentation
High current polarized proton source High energy proton polarimetry Control of spin coherence during acceleration + storage Spin sorted luminosity measurements
Physics
Probes directly sensitive to color charge Utilize Parity violation in W-production Large Q2 clean pQCD interpretation US-Japanese
collaboration at Brookhaven National Laboratory
RIKEN Radiation LaboratoryRIKEN BNL Research Center
Nucleon Spin Structure 11
June 6 th
at ultra-relativistic energiesthe proton represents a jetof quark and gluon probes
For example, direct photon production ~ probe gluon content with quark probes
)()(
)()( 21
1
1 xAxG
xGqqga
NN
NNA
LL
LL
The related double spin asymmetry:
RHIC SPIN: Proton Structure with Quark and Gluon Probes
quark
gluonquark
photon
experimental doublespin asymmetry
pQCD DIS?
12Nucleon Spin Structure June 6 th
Nucleon Helicity Structure
Quark spin ΔΣ , Δq(x) Gluon spin ΔG(x), ∫ ΔG(x)dx Orbital angular momentum Lz GPDs ?
Nucleon Spin Structure 13
June 6 th
Inclusive Measurements of g1p, g1
d and g1
n
Proton Neutron
HERMESΔƩ = 0.33 ± 0.011(th) ± 0.025 (exp) ± 0.028 (evo) at 5 GeV2
COMPASSΔƩ = 0.35 ± 0.03 (stat) ± 0.05 (syst) at 3 GeV2
Bjorken sum
S. Paul, X. Lu, H. Gao, INPC 2007
0.1821 ∓ 0.0019 (NNNLO)
Nucleon Spin Structure 14
June 6 th
Semi-Inclusive DIS: e+p e+ h +X Quark & Anti-Quark Helicity Distributions
u quarks large positive polarization
d quark have negative polarization
sea quarks (u, d, s ,s) compatible with 0in the measured x-range 0.02 < x < 0.6.
[HERMES, PRL92(2004), PRD71(2005)]
0.0430.002 u -
0.0350.054 d -
0.0340.028 s
x
Future:Precision DIS at JLAB-12 and at apossible electron – ion collider!
xΔu(x)
xΔd(x)
xΔu(x)
xΔd(x)
xΔs(x)
How well do we know hadron fragmentation functions ? new analysis of e+e- data, Hirai, Kumano, Nagai, Sudo hep-ph/0612009, INPC 2007
Possible Improvements
include e-p, p-p and e+e- in fragmentation function analysis done! De Florian, Sassot, Stratmann hep-ph/0703242
“add data” from b-factories e+e- hadrons
Nucleon Spin Structure 15
June 6 th
Belle MC
<1% of data sample work in progress
Possible Impact on the Knowledge of Hadron FFs from Analysis of b-Factory Data
z 2/
s
Ez
h
FF
FF
Compilation of dataavailable for the char-ged hadron FF
Belle MC: Charged h+/-, pions, kaons, protons
precision at high z!
h+,- pions kaons protons
Input for precision measurements of quark helicity distributions in SIDIS, with JLab-12 and a possible future electron- polarized proton collider.
Nucleon Spin Structure 16
June 6 th
Another Alternative:
W-production at RHIC
SIDIS: large x-coverage uncertainties from knowing fragmentation functions
Ws in polarized p-p: limited x-coverage high Q2 theoretically clean no FF-info needed
Hermes – 243 pb-1
PHENIX – 800 pb-1
Nucleon Spin Structure 17
June 6 th
Gluon Spin Contribution ΔG(x)
from scaling violation of world g1(x,Q2):Hirai, Kumano, SaitoPhys.Rev.D74:014015,2006
gP1(x,Q2)
ΔG=∫ΔG(x) dx = 0.47 ∓ 1.08 , Q2=1GeV2
Nucleon Spin Structure 18
June 6 th
Gluon Polarization from Photon Gluon Fusion in DIS
“direct” measurements
Photon-Gluon Fusion (PGF)
• golden channel: charm productiongolden channel: charm production
• hadron production at high Phadron production at high PTT
S. Paul, X. Lu INPC 2007
Favors small ΔG(x≈0.1)
Nucleon Spin Structure 19
June 6 th
2005 data
ALL also for , , J/
K.Aoki, R. Fatemi, B. SurrowINPC 2007
Gluon Polarization from Inclusive Hadrons and Jets in Polarized pp
Nucleon Spin Structure 20
June 6 th
2006: 7.5 pb-1 @ 60% polarisation
projections
Gluon Polarization from Inclusive Hadrons and Jets in Polarized pp
Nucleon Spin Structure 21
June 6 th
NLO QCD Analysis of DIS A1 + ALL(π0)
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
Only DIS ∫ΔG(x) dx = 0.47 ∓ 1.08 , Q2=1GeV2
Hirai, Kumano, SaitoPhys.Rev.D74:014015,2006
DIS + pp ∫ΔG(x) dx = 0.31 ∓ 0.32 , Q2=1GeV2
Nucleon Spin Structure 22
June 6 th
PHENIX π0 ALL vs GSA-LO and GSC-NLO
ALL
pT[GeV]
GSA-LO
GSC-NLO
PHENIX-2005
GSA-LO: ΔG = ∫ΔG(x)dx = 1.7
GSC-NLO: ΔG = ∫ΔG(x)dx = 1.0
Large uncertainties resultingfrom the functional form usedfor ΔG(x) in the QCD analysis!
GSA-LO and GSC-NLOcourtesy Marco Stratmannand Werner Vogelsang
Nucleon Spin Structure 23
June 6 th
ΔG(x) A, B and C from Gehrmann Stirling
present x-range
Much of the first momentΔG = ∫ΔG(x)dx might emerge from low x!
Some theoretical guidance:
ΔG(x) ≤ x G(x)
but G(X) diverges fasterthan x-1 !
NEED TO EXTENDMEASUREMENTS TOLOW x !!
Nucleon Spin Structure 24
June 6 th
Increase integrated luminosity by factor 10 (2008)
Extend measurements to low x Di-hadron Production extends (2008) measurements to x 0.01
NLO treatment available: Marco Stratmann -- INPC 2007
(EMC forward calorimeters available in STAR and PHENIX!)
Forward detector upgrades for direct (2011)photons and heavy flavor + electron cooling reach x 0.001
Polarized Electron Ion Collider measure ΔG(x) through scaling violations
Next Steps for ΔG(x) at RHIC
Nucleon Spin Structure 25
June 6 th
1
1
)0,,q()0,,q(2
1 xE xHxdxJ q
X. Ji, Phy.Rev.Lett.78,610(1997)
Generalized Parton Distributionsvs Orbital Angular Momentum ?
GPDs Hu, Hd, Eu, Ed provide access to total quark contribution to proton angular momentum in exclusiveprocesses l + N l’ + N + γ
½ = ½ (u+d+s) + Lq + Jg
J q
Proton spin sum
Nucleon Spin Structure 26
June 6 th
First Model Dependent Constraint of Ju vs JdE. Burtin, P. Bertin, X. Lu, INPC 2007
27Nucleon Spin Structure June 6 th
Transverse Spin
Transverse spin in hard scattering QCD Transversity and Collins Quark Fragmentation The Sivers Effect
Nucleon Spin Structure 28
June 6 th
Transverse Spin Phenomena in Hard Scattering QCD
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
Is QCD the correct theory of the strong interaction?
Experiment (E704, Fermi National Laboratory):
4q 10,20,3m example, N
qN AGeVsMeV
s
mA
QCD Test !
Nucleon Spin Structure 29
June 6 th
STARSTAR
Single Transverse Spin Asymmetries AN
at √=62.4 GeV and 200 GeV
Large single spin asymmetries persist at higher √s=62.4 and 200 GeV
√s=62.4 PHENIX and BRAHMS √s=200 GeV STAR
ANAN
xF
xF
M. ChiuINPC 2007
Nucleon Spin Structure 30
June 6 th
Inspect Factorized Expression for Cross Section
2P
)( 1xqi
)( 2xq j
11Px
22PxijLLa
1ps
Jet
Proton Structure
hard scattering reaction
fragmentationprocess
),(
)(ˆ)(),( ,
21
3
2,121
3
. Thqlkji
Tqi pzFFdxdx
qqqqdxqkxq
dzdxdx
Xppdlkj
fragmentationfunction
pQCD Proton Structure
small spindependence
(aLL~10-4)
Can initial and/or final state effects generate large transverse spin asymmetries? (ALL ~10-1)
Nucleon Spin Structure 31
June 6 th
Transverse Spin in QCD: Two Solutions
π+
π-
π0
(I) “Transversity” quark-distributions and Collins fragmentation
Correlation between proton- und quark-spin and spin dependent fragmentation
),()( 221
kzHxq
(II) Sivers quark-distribution
Correlation between proton-spin and transverse quark momentum
)(),( 21 zDkxf h
T
AN
xF
Collins FFQuark transversespin distribution
Sivers distribution
Nucleon Spin Structure 32
June 6 th
Collins Effect in the Quark- fragmentation into the Final State
sq
π
π sqp
p
= 0 AN =
NL - NR
NL + NR
Collins Effect NL : pions to the left
NR : pions to the right
q
qs
k
hph
,
hp
Collins Effect:Fragmentation of a transversely polarizedquark q into spin-less hadron h carries anazimuthal dependence:
sin
qh spk
Nucleon Spin Structure 33
June 6 th
π+ picks up L=-1 tocompensate for thepair S=1 and is emittedup.
u-quark absorbsphoton/gluon and flips it’s Spin.
Proton spin is pointing up!
String breaks anda dd-pair with spin1 is inserted.
A simple model to illustrate that spin-orbital angularmomentum coupling can lead to left right asymmetriesin spin-dependent fragmentation:
Artru Model for Collins Fragmentation
L = -1
Nucleon Spin Structure 34
June 6 th
Measurements of Quark Transversity Distributionsand Collins Fragmentation Functions (I) SIDIS
Collins Asymmetries in semi-inclusive deep inelastic scattering
e+p e + π + X
~ Transversity (x) x Collins(z)
New HERMES results for Collins AsymmetriesDiefenthaler, DIS 2007, Lu INPC 2007
AUT sin(s)
Nucleon Spin Structure 35
June 6 th
Collins Asymmetries in e+e-
annihilation into hadrons
e++e- π+ + π- + X
~ Collins(z1) x Collins (z2)
New Belle Collins AsymmetriesSeidl, DIS 2007
Measurements of Quark Transversity Distributionsand Collins Fragmentation Functions (II) e+e-
1hP
2hP
e-
e+
A12 cos(2)
PRELIMINARY
Nucleon Spin Structure 36
June 6 th
Anselmino, Boglione, D’Alesio,Kotzinian, Murgia, Prokudin, TurkPhys. Rev. D75:05032,2007
HERMES SIDIS
+ COMPASS SIDIS
+ Belle e+e-
transversity dist.
+ Collins FF
Fit includes:
First Extraction of Quark Transversity Distributionsand Collins Fragmentation Functions SIDIS + e+e-
Nucleon Spin Structure 37
June 6 th
The Sivers Effect
proton
Sp
Sp
proton
Sivers function:D. Sivers 1990
Sivers:
Correlation between the transverse spin of theproton and the transverse momentum kT of quarks and gluons in the proton (link to orbitalangular momentum?)
M
SkPkxfxqA PTq
TN
)ˆ(
),()( 2211Observed asymmetry:
Nucleon Spin Structure 38
June 6 th
Sivers Asymmetries at HERMES and COMPASS
implies non-zero Lq
Nucleon Spin Structure 39
June 6 th
Sivers Effect and Orbital Angular Momentum
M. Burkardt
>
Nucleon Spin Structure 40
June 6 th
The Sivers Effect : Needs Final State Soft Gluon Exchange
M. Burkardt
Nucleon Spin Structure 41
June 6 th
What have we learned from this?
The Sivers effect arises from soft gluon interactions in thefinal state (SIDIS) or initial state (Drell Yan).
Need to modify naïve concepts of factorization whichreduce hard scattering to partonic processes and neglect softgluon interactions in the initial or final state: hard scatteringmatrix elements are modified with gauge link integrals thataccount for initial and final state soft gluon exchange.
A modified concept of universality has been obtained which showshow the presence of initial or final state interactions can impacttransverse momentum dependent distribution; eg. the Siversfunction changes sign between SIDS and Drell Yan!
There may be exciting applications elsewhere, eg. other transversemomentum dependent effects or the understanding nuclear effects in hard scattering.
Nucleon Spin Structure 42
June 6 th
Goals for the Future
Quantitative understanding of transverse spin phenomena in QCD
Do Sivers and Collins mechanisms reconcile QCD with transverse spin phenomena?
Precision measurements of transversity distributions and Collinsfragmentation function measurements.
This will complete the experimental survey of the nucleon at leading twist. Determine sum of first moments (tensor charge) which can be compared to lattice calculations.
Survey Sivers and Boer Mulders effects in SIDIS and pp
Fundamental understanding of factorization and universality in hard scattering.
Relation to orbital angular momentum ?!
Future results expected from COMPASS, RHIC, JLAB, Belle, JLAB-12-GEV, JPARC FAIR and EIC. This includes high precision measurements in e-p, e-e and p-p possibly first systematic study of factorization + universality
Nucleon Spin Structure 43
June 6 th
Transversity : correlation between transverse proton spin and quark spin
Sivers : correlation between transverse proton spin and quark transverse momentum
Boer/Mulders: correlation between transverse quark spin and quark transverse momentum
Transversity, Sivers and Boer Muldersin the Proton Wavefunction
)( 2xq
),( 221
kxf qT
),( 211
kxh q
Sp– Sq – coupling ?
Sp- Lq– coupling ??
Sq- Lq– coupling ??
Nucleon Spin Structure 44
June 6 th
Summary
Bjorken sum rule holds
Integral quark spin contributions are well known
Δq(x), Δq(x) only well known for up-quarks only
Hints that ΔG(x) is small at x~0.1. ∫ΔG(x)dx remains largely unconstraint RHIC luminosity, low-x
Possible route to OAM through
Exp. Observation of Sivers and Collins asymmetriesTheoretical advance in understanding TMD + concepts of factorization and universality
Plenty of work for theory + existing and future experimental tools!
Nucleon Spin Structure 45
June 6 th
Sivers in SIDIS and Drell Yan vsFactorization and Universality
Nucleon Spin Structure 46
June 6 th
Transverse Spin Drell Yan at RHIC vs
π-Sivers Asymmetry in Deep Inelastic Scattering
• Important test at RHIC of the fundamental QCD prediction of the non-universality of the Sivers effect!
• requires very high luminosity (~ 250pb-1)
Nucleon Spin Structure 47
June 6 th
Simple QEDexample:
DIS: attractive Drell-Yan: repulsiveSame in QCD:
As a result:
Non-universality of Sivers Asymmetries:Unique Prediction of Gauge Theory !
Nucleon Spin Structure 48
June 6 th
0.1 0.2 0.3 x
Siv
ers
Am
plitu
de
0
Experiment SIDIS vs Drell Yan: Sivers|DIS= − Sivers|DY
*** Test QCD Prediction of Non-Universality ***
HERMES Sivers Results
Markus DiefenthalerDIS WorkshopMűnchen, April 2007
0
RHIC II Drell Yan Projections
Nucleon Spin Structure 49
June 6 th
I) Can one extract G(x,Q2) from pp?
II) NLO pQCD vs RHIC data
Is pQCD applicable at RHIC?
Nucleon Spin Structure 50
June 6 th
Global QCD Analysis for G(x,Q2) and q(x,Q2):
J. Pumplin et.al JEHP 0207:012 (2002)
3.16GeVQ at u
3.16GeVQ at d
10-410-3 10-2 10-1 0.5 x
gluon
down
up-quarks
anti-down
Quark and Gluon Distributions
error on G(x,Q2)
error for u(x,Q2)
+/- 10%
+/- 5% +/- 5%
error for d(x,Q2)
10-410-3 10-2 10-1 0.5 x
CTEQ6: use DGLAP Q2-evolution of
quark and gluon distributions to extract q(x,Q2)and G(x,Q2) from global fit to data sets at different scales Q2.
H1 + Zeus F2
CDF + D0 Jets
CTEQ5M1
CTEQ6M
Nucleon Spin Structure 51
June 6 th
G(x,Q2) and q(x,Q2) + pQCD beautifully agree Tevatron + HERA!
J. Pumplin et.al JEHP 0207:012 (2002)
D0 Jet Cross Section ZEUS F2
Nucleon Spin Structure 52
June 6 th
and at RHIC ? q(x,Q2), G(x,Q2) and D(z,Q2) + pQCD are nicely consistent with experiment!
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 !?
Nucleon Spin Structure 53
June 6 th
• NLO-pQCD calculation– Private communication with
W.Vogelsang– CTEQ6M PDF.– direct photon + fragmentation photon– Set Renormalization scale and factorization scale pT/2,pT,2pT
Theory calculation show good agreement with the experimentalcross section.
Direct Photons: NLO pQCD vs RHIC data
Nucleon Spin Structure 54
June 6 th
W
Z
W Production in Polarized pp Collisions
Single Spin Asymmetry in the naive Quark Parton Model
GeV 20
for dominates
Tp
W
2121
21 ,
),(
),(xx
Mxu
MxuA
W
WWL
Experimental Requirements: tracking at high pT
event selection for muons difficult due to hadron decays and beam backgrounds
control of all backgrounds
Parity violation of the weakinteraction in combination withcontrol over the proton spin orientation gives access to theflavor spin structure in the proton!
Nucleon Spin Structure 55
June 6 th
Extraction of quark polarizations at LO
Machine and detector requirements:Machine and detector requirements:
– ∫Ldt=800pb-1, P=0.7 at √s=500 GeV
– trigger upgrade
– Control of backgrounds
contributions both from
FVTX and NCC!
2009 to 2012 running at √s=500 GeVis projected to yield ∫Ldt ~950pb-1
Nucleon Spin Structure 56
June 6 th
Run 5 ALL(): First constraints for ∆G(x)
¨
standard ∆G from DIS
∆G =0
PHENIX
max
∆G from
DIS
min ∆G possible curves: comparison with ALL obtained with ∆G from deep Inelastic lepton nucleon scattering
(M. Glück, E. Reya, M. Stratmann, und W. Vogelsang, Phys. Rev. D 53 (1996) 4775).
PANIC, October 2005
Asymmetries are consistentwith gluon spin contributionsfrom ʃ∆G(x)dx ~ 0 to 0.5
Nucleon Spin Structure 57
June 6 th
EMC-RICH Trigger (RBRC/UIUC, UCR, Tokyo)
Information from EMC (172 elements with4 energy thresholds) and RICH (256 ele-ments with one threshold) is used to tag high energy electrons and photons:
Physics (p-p, d-Au) :
/,,for ,, 000
Jdp
dAA
TLL N
EM
C T
rigge
r E
ffici
ency
Nucleon Spin Structure 58
June 6 th
Final results on ∆G will come from combined NLO analysis of RHIC and DIS
RHIC measurements will span broad range in x with good precision. Multiple channels with independent theo. and exp. uncertainties.
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/
Nucleon Spin Structure 59
June 6 th
Sivers Function in PHENIX: The Muon Piston Calorimeter (MPC)
Measure the Sivers function through the asymmetry AN in hadron-hadron correlationen, for neutral pions (Boer and Vogelsang Phys.Rev.D69:094025,2004) 0
0
AN Jets
Hadron Paare
∫Ldt = 0.35pb-1 (Run 3)
Nucleon Spin Structure 60
June 6 th
First attempt at lower x: ALL(2π0)
from Les Bland (for STAR FMS)Measure ALL for neutralpion pairs: one in the centralarm the second in the MPC
0.1 > x 0.001 !
MPC
Nucleon Spin Structure 61
June 6 th
NCC direct photons
ΔG(x) – x-range with Detector Upgrades
Nucleon Spin Structure 62
June 6 th
K.Aoki, R. Fatemi, B. SurrowINPC 2007
Gluon Polarization from Inclusive Hadrons and Jets in Polarized pp