nucleon spin structure...rhic polarimetry (i) measurement of degree of polarization • elastic p-p...
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Nucleon Spin StructureLongitudinal Spin of the Proton
HUGS Summer SchoolJefferson National Laboratory
June 1-3, 2011 Lecture 4 of 6
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Introduction & Overview (II)
• Lecture 4 & Lecture 5– Relativistic Heavy Ion Collider as a Polarized Collider– Comments experimental techniques– Review of results– Principle limitations
• Lecture 6: Future studies in nucleon spin– Review of all experimental limitations– Non-Longitudinal spin structure of the proton– Status and possibilities at an Electron Ion Collider (EIC)
2Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Complementary techniques
Photons colorless: forced to interact at NLO with gluons
Can’t distinguish between quarks and anti-quarks either
Why not use polarized quarks and gluons abundantly available in protons as probes ?
3Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
The RHIC Spin Program
4Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
The RHIC Spin Program• Direct determination of polarized gluon distribution via
multiple probes ( π0/+/-, γ, c-cbar,… production) – Double longitudinal helicity asymmetry: ALL
4Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
The RHIC Spin Program• Direct determination of polarized gluon distribution via
multiple probes ( π0/+/-, γ, c-cbar,… production) – Double longitudinal helicity asymmetry: ALL
4Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
The RHIC Spin Program• Direct determination of polarized gluon distribution via
multiple probes ( π0/+/-, γ, c-cbar,… production) – Double longitudinal helicity asymmetry: ALL
• Direct determination of anti-quark polarization using production and parity violating decay of W+/- – Single longitudinal spin asymmetry: AL
4Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
The RHIC Spin Program• Direct determination of polarized gluon distribution via
multiple probes ( π0/+/-, γ, c-cbar,… production) – Double longitudinal helicity asymmetry: ALL
• Direct determination of anti-quark polarization using production and parity violating decay of W+/- – Single longitudinal spin asymmetry: AL
4Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
The RHIC Spin Program• Direct determination of polarized gluon distribution via
multiple probes ( π0/+/-, γ, c-cbar,… production) – Double longitudinal helicity asymmetry: ALL
• Direct determination of anti-quark polarization using production and parity violating decay of W+/- – Single longitudinal spin asymmetry: AL
• Systematic study of transverse spin phenomena– Single transverse spin collisions – Possible connections: Orbital Angular Momentum (OAM)?
4Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
The probes and techniques at RHIC
5Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
RHIC as a Polarized Proton Collider
6
BRAHMS
STAR
PHENIX
AGS
LINACBOOSTER
Pol. H-‐ Source
Spin Rotators(longitudinal polarizaBon)
Siberian Snakes
200 MeV Polarimeter
Internal Polarimeter
pC PolarimetersAbsolute Polarimeter (H↑ jet)
pC Polarimeter10-‐25% Helical ParBal Siberian Snake
5.9% Helical ParBal Siberian Snake
PHOBOS
Spin Rotators(longitudinal polarizaBon)
Spin flipper
Siberian Snakes
Without Siberian snakes: νsp = Gγ = 1.79 E/m → ~1000 depolarizing resonancesWith Siberian snakes (local 180¡ spin rotators): νsp = ½ → no first order resonancesTwo parBal Siberian snakes (11¡ and 27¡ spin rotators) in AGS
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Siberian Snakes
7
Ø AGS Siberian Snakes: variable twist helical dipoles, 1.5 T (RT) and 3 T (SC), 2.6 m long
Ø RHIC Siberian Snakes: 4 SC helical dipoles, 4 T, each 2.4 m long and full 360° twist
2.6 m 2.6 m
RIKEN
RIKEN
RIKEN RIKEN
DOE
Courtesy of A. LuccioThursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Polarized Collider Development
8
Parameter Unit 2002 2003 2004 2005 2006 Design
No. of bunches -- 55 55 56 106 111 111
bunch intensity 1011 0.7 0.7 0.7 0.9 1.4 2.0
store energy GeV 100 100 100 100 100 100250
β* m 3 1 1 1 1 1
peak luminosity 1030cm-2s-1 2 6 6 10 35 80
average luminosity 1030cm-2s-1 1 4 4 6 20 60
Collision points -- 4 4 4 3 2 2
average polarization, store % 15 35 46 47 60 70
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Since 2006: more data, 200 and 500 GeV
9
Run (End Year) √s (GEV) L recorded(pb-‐1)
PolarizaBon FOM (P4*L)
Run 06 200 7.5 57% 0.79Run 06 62.4 0.08 48% 0.0042Run 09 200 16 57% 1.5Run 09 500 14 39% 0.21Run 11 500 25 45 1.03
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Polarization at 100 GeV
10Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
A typical store at 100 GeV
11
19:00 21:00 23:00 01:00 03:00
20
40
60
0
50
0
0
10
20
PolarizaB
on [%
]Luminosity
[103
0 cm
-‐2 s-‐
1 ]Proton
s [10
11]
Start of collisionsStart of acceleraBon ramp
60 % polarizaBon
100
150
30
CollimaBon complete
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
RHIC beam polarimetry
How do we know the proton beams are polarized?Polarimetry had to be developed
How do we know that they are longitudinally polarized?Stable direction of spins in the storage ring is vertical, spin rotator magnets rotate them. How do we know they are doing their job?
12Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
RHIC polarimetry (I)Measurement of degree of polarization
• Elastic p-p Coulomb Nuclear Interference (CNI) measures absolute polarization employing a polarized Hydrogen-Jet (as target)
• Elastic p-Carbon CNI polarimeter monitors the degree of polarization with multiple measurements during fills
• Both together succeeded in getting an uncertainty in the polarization measurement of +/- 4.7%
13Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 14
Beam polarization measurement (1)
• Use single spin asymmetry in elastic scattering of p-p and p-Carbon – Coulomb Nuclear
Interference (CNI) kinematics
Top viewLeft
Right
For a known/understood scakering process, measure the single spin asymmetry and calculate the beam polarizaBon.
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 15
RHIC Absolute Polarization
• Calculation by Shwinger 1946
• Unknown spin-flip amplitude
• Now found to be zero
Very forward scattering
ElasBc p-‐p scakering single spin asymmetry as a funcBon of momentum transfer t
PLB 638 (2006) 450GeV
QED Spin Flip
RHIC-‐AGS Best Thesis Award 2006, Hiromi Okada
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
RHIC polarimetry (I)
Determination and monitoring of spin vector direction in the interaction region
• Employs (accidentally discovered in 2002) single transverse spin asymmetry in “forward” neutron production
• “Local Polarimeters”: at PHENIX, now at STAR as well
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 17
PHENIX* Local Polarimeter
(±2mrad)
~1800cm
10cm
PHENIX Collision Point
Blue beam Yellow beam
*Now also STAR
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 17
PHENIX* Local Polarimeter
(±2mrad)
~1800cm
10cm
PHENIX Collision Point
Blue beam Yellow beam
Blue Yellow
Blue Yellow
*Now also STAR
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 17
PHENIX* Local Polarimeter
(±2mrad)
~1800cm
10cm
PHENIX Collision Point
Blue beam Yellow beam
Blue Yellow
Blue Yellow
PL/P > 0.99 blue & yellow
*Now also STAR
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 18
Measured Asymmetry During Longitudinal Running
<PT/P>=10±2(%)<PL/P> =99.48±0.12±0.02(%)
LR χ2/NDF = 88.1/97p0 = -0.00323±0.00059
LR
UD χ2/NDF = 82.5/97p0 = 0.00423±0.00057
XF>0 XF>0
XF<0 XF<0
χ2/NDF = 119.3/97p0 = 0.00056±0.00063
UD χ2/NDF = 81.7/97p0 = -0.00026±0.00056
Fill NumberFill Number
<PT/P>=14±2(%)<PL/P>=98.94±0.21±0.04(%)
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 18
Measured Asymmetry During Longitudinal Running
<PT/P>=10±2(%)<PL/P> =99.48±0.12±0.02(%)
LR χ2/NDF = 88.1/97p0 = -0.00323±0.00059
LR
UD χ2/NDF = 82.5/97p0 = 0.00423±0.00057
XF>0 XF>0
XF<0 XF<0
χ2/NDF = 119.3/97p0 = 0.00056±0.00063
UD χ2/NDF = 81.7/97p0 = -0.00026±0.00056
Fill NumberFill Number
<PT/P>=14±2(%)<PL/P>=98.94±0.21±0.04(%)
• Measurement of remaining transverse component à spin pakern is correct
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 18
Measured Asymmetry During Longitudinal Running
<PT/P>=10±2(%)<PL/P> =99.48±0.12±0.02(%)
LR χ2/NDF = 88.1/97p0 = -0.00323±0.00059
LR
UD χ2/NDF = 82.5/97p0 = 0.00423±0.00057
XF>0 XF>0
XF<0 XF<0
χ2/NDF = 119.3/97p0 = 0.00056±0.00063
UD χ2/NDF = 81.7/97p0 = -0.00026±0.00056
Fill NumberFill Number
<PT/P>=14±2(%)<PL/P>=98.94±0.21±0.04(%)
Developed in Run-5, now routine operation
• Measurement of remaining transverse component à spin pakern is correct
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
ΔG MEASUREMENTS
19Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 20
PHENIX Detector at RHIC• Design philosophy:
– High resolution limited acceptance– High rate capability DAQ– Excellent triggers for rare events
• Central arm– Tracking: Drift chambers, pad
chambers, time expansion chamber– Superb EM Calorimetry PbGl, PbSc ΔφxΔη~0.01 x 0.01 π0 to 2γ resolved up to 25 GeV pT– Particle Identification: RICH, TOF
• Forward Muon Arms:– Muon tracker, muon identifiers
• Global detectors:– Beam beam collision (BBC) counter,
Zero Degree Calorimeters (ZDCs)• Online monitoring, calibration and
production
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 21
STAR Detector at RHIC
• Design Philosophy:•Maximize acceptance• lower resolution
•Subsystems:• φ = 2π acceptance in EM calorimetry
Barrel and EndCapTotal: -1 < η < 2
• Time Projection Chamber• Separate Forward pion detector • Silicon vertex tracker• Beam-Beam Counters• Zero Degree Calorimeter
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 22
Measuring ALL
(N) Yield (R) Relative Luminosity(P) Polarization
ü Bunch spin configuration alternates every 106 ns ü Data for all bunch spin configurations are collected at the same time⇒ Possibility for false asymmetries are greatly reduced
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 22
Measuring ALL
(N) Yield (R) Relative Luminosity(P) Polarization
ü Bunch spin configuration alternates every 106 ns ü Data for all bunch spin configurations are collected at the same time⇒ Possibility for false asymmetries are greatly reduced
Exquisite control over false asymmetries due to ultra fast rotaBons of the target and probe spin.
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Hadron-Hadron Collisions: Observables• Do not know the initial energy,
orientation about the incoming partons
• A hadron created in the collision:– Measure its Transverse
momentum with a solenoid-al magnetic field: pT (GeV/c)
– Angle with respect to the beam direction θ leads to psudorapidity:
23
θ
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 24
Calibration of our probes…
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 24
Calibration of our probes…• Measurement of a cross section involves:
– Detailed understanding of the luminosity– Detailed understanding of the detector
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 24
Calibration of our probes…• Measurement of a cross section involves:
– Detailed understanding of the luminosity– Detailed understanding of the detector
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 24
Calibration of our probes…• Measurement of a cross section involves:
– Detailed understanding of the luminosity– Detailed understanding of the detector
• Comparison of the data with theory: if they agree:– Theoretical framework applicable in this kinematic
regime– Double spin asymmetries can be interpreted in terms of
polarized gluon distributions
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 24
Calibration of our probes…• Measurement of a cross section involves:
– Detailed understanding of the luminosity– Detailed understanding of the detector
• Comparison of the data with theory: if they agree:– Theoretical framework applicable in this kinematic
regime– Double spin asymmetries can be interpreted in terms of
polarized gluon distributions
• An extremely important check: Imperative for all measurements we publish
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 25
Un-polarized π0 Cross Section: 200 GeV CM
|η|<0.35
STAR: π0 high rapidity (forward)PRL 97, 152302
PHENIX: π0 mid-‐rapidity (central)hep-‐ex-‐0704.3599
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 25
Un-polarized π0 Cross Section: 200 GeV CM
Good agreement between NLO pQCD calculaXons and dataComparison fails at lower energies
|η|<0.35
STAR: π0 high rapidity (forward)PRL 97, 152302
PHENIX: π0 mid-‐rapidity (central)hep-‐ex-‐0704.3599
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 26
Unpol. Cross Section in ppPHENIX: pp→γ X
PRL 98, 012002STAR: pp→jet XPRL 97, 252001
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 26
Unpol. Cross Section in ppPHENIX: pp→γ X
PRL 98, 012002STAR: pp→jet XPRL 97, 252001
Excellent agreement between NLO pQCD calculaXons and data
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Accessing ΔG in p+p Collisions at RHIC
• If Δf = Δq, then we have this from pDIS• So roughly, we have
where the coefficients a, b and c depend on final state observable and event kinematics (η,pT).
+-‐ = ++
++=
From ep (&pp)(HERA mostly)
NLO pQCDFrom e+e-(& SIDIS,pp)
27Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Accessing ΔG in p+p Collisions at RHIC
• If Δf = Δq, then we have this from pDIS• So roughly, we have
where the coefficients a, b and c depend on final state observable and event kinematics (η,pT).
+-‐ = ++
++=
From ep (&pp)(HERA mostly)
NLO pQCDFrom e+e-(& SIDIS,pp)
27Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Accessing ΔG in p+p Collisions at RHIC
• If Δf = Δq, then we have this from pDIS
+-‐ = ++
++=
From ep (&pp)(HERA mostly)
NLO pQCDFrom e+e-(& SIDIS,pp)
27Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Accessing ΔG in p+p Collisions at RHIC
• If Δf = Δq, then we have this from pDIS• So roughly, we have
+-‐ = ++
++=
From ep (&pp)(HERA mostly)
NLO pQCDFrom e+e-(& SIDIS,pp)
27Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Accessing ΔG in p+p Collisions at RHIC
• If Δf = Δq, then we have this from pDIS• So roughly, we have
+-‐ = ++
++=
From ep (&pp)(HERA mostly)
NLO pQCDFrom e+e-(& SIDIS,pp)
27Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Accessing ΔG in p+p Collisions at RHIC
• If Δf = Δq, then we have this from pDIS• So roughly, we have
+-‐ = ++
++=
From ep (&pp)(HERA mostly)
NLO pQCDFrom e+e-(& SIDIS,pp)
27Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Accessing ΔG in p+p Collisions at RHIC
• If Δf = Δq, then we have this from pDIS• So roughly, we have
where the coefficients a, b and c depend on final state observable and event kinematics (η,pT).
+-‐ = ++
++=
From ep (&pp)(HERA mostly)
NLO pQCDFrom e+e-(& SIDIS,pp)
27Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
2005, 2006 Run Data Sets Analyzed
• 2005 • 2006 Preliminary
• 2005: PRD76, 05116• 2006: arXiv:0810.0694 (PRL)
28
GRSV: NLO Fit to the polarized DIS data to extract polarized gluon distribuBonPRD63, 094005 (2001)
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
1st step: truly global NLO QCD fit• D. deFlorian et al, PRL 101, 072001 (2008)• Includes PHENIX Inclusive π0 at 200 and 62 GeV and
STAR inclusive Jets at 200 GeV along with world’s polarized DIS data sets à Resulting ΔG is small, with large uncertainties
29Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011 30
ΔG(x) @ Q2=10 GeV2
• Global analysis: DIS, SIDIS, RHIC-Spin
• Uncertainly on ΔG large: Need more low-x measurements!
de Florian, Sassot, Stratmann & Vogelsang
Present
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
What about the anti-quark polarization?
• DIS probe (γ*) doesn’t distinguish q from qbar– Has to take measure semi-inclusive (π, K production)– Uncertainties in fragmentation functions
• High energy p-p collisions enable probing q,qbar through W+/- production –> Plan at RHIC
31Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Many others… luminosity deprived…
32Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Many others… luminosity deprived…
32
STAR neutral pions: central rapidity
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Many others… luminosity deprived…
32
STAR neutral pions: central rapidity
STAR neutral pions: forward rapidity
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Many others… luminosity deprived…
32
STAR neutral pions: central rapidity
STAR neutral pions: forward rapidity
PHENIX charged pions: central rapidity
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Many others… luminosity deprived…
32
STAR neutral pions: central rapidity
STAR neutral pions: forward rapidity
PHENIX charged pions: central rapidity
PHENIX η: central rapidity
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Many others… luminosity deprived…
32
STAR neutral pions: central rapidity
STAR neutral pions: forward rapidity
PHENIX charged pions: central rapidity
PHENIX η: central rapidity
PHENIX Direct Photon: central rapidity
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Many others… luminosity deprived…
32
STAR neutral pions: central rapidity
STAR neutral pions: forward rapidity
PHENIX charged pions: central rapidity
PHENIX η: central rapidity
PHENIX Direct Photon: central rapidity
A large luminosity increaseHave occurred since 2009.Many new probes of ΔG are
expected to be available for futuremeasurements…. Stay tuned.
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Principle Limitations
33Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Principle Limitations
• Overlapping x for pT bins
33Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Principle Limitations
• Overlapping x for pT bins• Need more exclusive
measurements (Luminosity)– γ-Jet (PHENIX VTX upgrade)
33Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Principle Limitations
• Overlapping x for pT bins• Need more exclusive
measurements (Luminosity)– γ-Jet (PHENIX VTX upgrade)
33
present (π0)x-range√s = 200 GeV
Extend to lower x at √s = 500 GeV
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Principle Limitations
• Overlapping x for pT bins• Need more exclusive
measurements (Luminosity)– γ-Jet (PHENIX VTX upgrade)
• Limited x-range
33
present (π0)x-range√s = 200 GeV
Extend to lower x at √s = 500 GeV
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Principle Limitations
• Overlapping x for pT bins• Need more exclusive
measurements (Luminosity)– γ-Jet (PHENIX VTX upgrade)
• Limited x-range• Need to widen it…
Higher and lower Center of Mass OperationPHENIX measured at 62 GeV CM
33
present (π0)x-range√s = 200 GeV
Extend to lower x at √s = 500 GeV
Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Summary & Outlook
34Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Summary & Outlook• RHIC Spin program has come of age; it has provided many
important clues toward solving the nucleon spin puzzle
34Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Summary & Outlook• RHIC Spin program has come of age; it has provided many
important clues toward solving the nucleon spin puzzle
34Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Summary & Outlook• RHIC Spin program has come of age; it has provided many
important clues toward solving the nucleon spin puzzle
• Measurements of ΔG ongoing: Indicate little contribution to nucleon spin from the kinematic region accessed so far– Different center of mass energies & kinematics needs to
be explored.
34Thursday, June 2, 2011
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6/2/2011Abhay Deshpande, Nucleon Spin Lectures 4 of 6 at HUGS 2011
Summary & Outlook• RHIC Spin program has come of age; it has provided many
important clues toward solving the nucleon spin puzzle
• Measurements of ΔG ongoing: Indicate little contribution to nucleon spin from the kinematic region accessed so far– Different center of mass energies & kinematics needs to
be explored.
• Focus of RHIC Spin program moving to W physics and a systematic study of transverse spin phenomena
34Thursday, June 2, 2011