spin structure functions - some topics for a future eic
DESCRIPTION
Spin structure functions - some topics for a future EIC. Sebastian Kuhn ODU. Things to measure:. g 1p,d,n : Evolution, low x extrapolation => Better determination of G, Bjorken and Burkhardt-Cottingham sum rules,… SIDIS: s, u - d, …; k T dependence - PowerPoint PPT PresentationTRANSCRIPT
Spin structure functions - some topics for a future EIC
Sebastian Kuhn
ODU
Things to measure:
• g1p,d,n: Evolution, low x extrapolation
=> Better determination of G, Bjorken and
Burkhardt-Cottingham sum rules,…
• SIDIS: s, u - d, …; kT dependence
• Spin EMC effect with spectator tagging
• Target fragmentation (e.g., self-analyzing
decay)
Existing Data for p and d
xbj
A1d ( D-state corrected ) HF perturbed QM
World Data Parm + d WF Q2 = 4.2 GeV2
World Data parm Q2 = 10 GeV2
Spin 3/2 suppression
Helicity 3/2 suppression
Symmetric Q Wave function suppression
SLAC - E143
SMC
HERMES
SLAC - E155
CLAS-EG1b Q2 = 1.0 - 4.52 GeV2
SU(6)
pQCD
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Isgur, PRD 59, 034013 (2003)
}
Close and Melnitchouk, PRC 68, 035210 (2003)
xbj
A1p
HF perturbed QM
World Data parm Q2 = 10 GeV2
Spin 3/2 suppression Helicity 3/2 suppression
Symmetric Q Wave function
SLAC - E143
SMC
HERMES
SLAC - E155
CLAS-EG1b Q2 = 1.0 - 4.52 GeV2
SU(6)
pQCD
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Proton
Deuteron
W > 2; Q2 > 1
Predicted Data from CLAS12Proton Deutero
nW > 2; Q2 > 1
Existing and proposed data for the neutron
Improvements in u, d, G, s expected before EIC
Note: Decreased uncertainties below x = 0.05 misleading (artifact of over-constrained fit)
Present knowledge ofs and G (ca 2008)
Kinematic Coverage (DIS)
Jlab at 12 GeV
DIS - low x
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1
x
g1d
Q2 1-4
Q2 4-16
Q2 9-36
Q2 25-100
COMPASS '07
SLAC E155
Assume 10 GeV e- on 30 GeV d, Luminosity 1033/s/cm2, 100 days
Status of first moments
€
⇐ g1(x,Q2)dx
0
1
∫
€
g2(x,Q2)dx
0
1
∫ ⇒
Flavor Decomposition from SIDIS
QuickTime™ and a decompressor
are needed to see this picture.
(copied from a talk by Pawel Nadel-Turonski)
Concluding Thoughts
• Even at modest energy and luminosity, it looks like we can make significant progress on spin structure
• Obviously, I need to do some real work before making any firmer conclusions
• Obvious upgrade path towards lower x as cm energy increases
• We should stop thinking about DIS, SIDIS, PVDIS,… as different topics - instead, use unified EW theory as a comprehensive probe of inclusive nucleon structure, getting information from all structure functions F1 - F3, g1 - g5 (, -Z, W)