1. Spin Duality on the Neutron (3He)
Patricia Solvignon
Temple University
For the JLAB Hall A and E Collaborations
Motivations
Quark-Hadron Duality was first observed in the 70’s by Bloom and Gilman on the spin independent structure function F2. They realized that the nucleon resonances average on the high Q2 scaling curve when an appropriate scaling variable is used.
Recent data on proton spin independent and dependent structure functions measured in the resonance region indicate the onset of Quark-Hadron Duality.
The goal of the experiment E is to provide precision data on the neutron spin structure function in order to:
 understand the transition between partons and hadrons
 study the interactions between quarks and gluons
 investigate the spin and flavor dependence of Quark-Hadron Duality
 access the high xbj region, where theoretical models predictions for A1 are very different, if duality is demonstrated and well understood.
Experimental setup
The experiment ran in Hall A at Jefferson Lab in January-February We used:
Preliminary results
Spin structure function g1(3He)
Polarized electron beam at 3.0, 4.0 and 5.0 GeV with Pavg=77%.
High Resolution Spectrometers in symmetric configuration at 25o and 32o  double the statistics and control of the systematics.
Particle identification with Cerenkov counter combined with EM calorimeter  reduce pion contamination by a factor of 104, while keeping electron efficiency above 99%.
Hall A polarized 3He target:
based on spin exchange between optically pumped Rb and 3He. A little amount of N2 is added as buffering gas.
longitudinal and transverse configurations
high luminosity: 1036 s-1 cm-2
Two independent polarimetries: NMR and EPR
average polarization during the experiment: Pavg=37%
Spin asymmetry A1(3He)
The E experiment
Inclusive experiment : 3He(e,e)X
Measure polarized cross sections and asymmetries in the resonance region for 1.0<Q2<4.0(GeV/c)2
Form g1, g2, A1 and A2 for 3He 
Test Duality on the neutron spin structure functions  
Data analysis
Structure functions
Generate asymmetries and unpolarized cross sections
Extract g1 and g2 directly from our data
(N+/ Q+ LT+)-(N-/ Q- LT-)
A/ / () raw = 
(N+/ Q+ LT+)+(N-/ Q- LT-)
MQ2 E
g1 =   
4e E´ E + E´
Spin asymmetry A2(3He)
(// + tan(/2)  )
Ncut Ntrial
oraw =  
Ninc 3He det LT Nacc Ltarg p 
E + E´ cos

E´sin
MQ2
g2 =  
4e E´(E +E´)
(- // +
 )
Apply correction for nitrogen dilution
A/ / () exp = A/ / () raw /(fN2 Ptarg Pbeam)
oexp = oraw - 2(N2/ 3He)N
Need external input of R to form A1 and A2
A//  A
A1 =  - 
D(1+ ) d(1+ )
Form polarized cross section differences
//() exp = 2 A //()exp o exp
 A// A
A2 =  + 
D(1+ ) d(1+ )
Apply radiative corrections on //() and o
//()= //() exp + R.C.
A//()= //() / 2oborn
Preliminary interpretations
(D and d depend on R)
For Q2<2.0(GeV/c)2, the (1232) is large and negative for both g1 and A1.
For Q2>2.0(GeV/c)2, the (1232) vanishes while the non-resonant background is rising. Thus the g1 resonance data oscillate around the DIS fit (no Q2-evolution) showing a hint of Quark-Hadron Duality for g1(3He). A1(3He) from resonance is now positive at high x following the same trend as the DIS data and seems to show no strong Q2-dependence.
As for A2(3He), all Q2 settings show the same behavior of going negative at large x and agree well with the DIS data
From 3He to neutron
Conclusion
The polarized 3He target is used as an effective neutron target and because of the dominant S state, the neutron spin structure functions are expected to show the same behavior as 3He ones since the effect of the two protons should be small.
E provides precision data on the spin structure functions on neutron (3He) for 1.0<Q2<4.0(GeV/c)2.
Direct extraction of g1 and g2 from our data.
Test of Quark-Hadron Duality for neutron and 3He spin structure functions by comparing E data with DIS data.
E data combined with proton data allow us to study the spin and flavor dependence of duality.
Our data can also be used to extract moments of SSF (e.g. d2).