1. Measurement of neutron spin asymmetry A 1 n in the valence quark region using the Solenoid Nilanga Liyanage University of Virginia

2. Outline Physics: Neutron spin structure at high x: test fundamental predictions of nucleon structure. flavor decomposition of polarized pdfs  One of the most exciting experiments awaiting 12 GeV beam Technology: high energy beam highest possible polarized luminosity large acceptance spectrometers

3. Inclusive Electron Scattering 4-momentum transfer squared Invariant mass squared Bjorken variable Unpolarized case { Polarized case {

4. Virtual Photon Asymmetry N h N =+ h q =+ h  =+ h q =+  1/2 N h N =- h q =+ h  =+ h q =+  3/2

5. Nucleon Model F 2 n /F 2 p d/u  u/u  d/d A1nA1nA1nA1n A1pA1pA1pA1p SU(6)2/31/22/3-1/305/9 Valence Quark 1/401-1/311 pQCD3/71/51111 Neutron Wavefunction (Spin and Flavor Symmetric) Nucleon Structure at large x Bj 11 110 )( 3 2 )( 3 1 )( 3 1 )( 18 1 )( 2 1     SS SSS ddu u udd d dn

6. Nucleon Model F 2 n /F 2 p d/u  u/u  d/d A1nA1nA1nA1n A1pA1pA1pA1p SU(6)2/31/22/3-1/305/9 Valence Quark 1/401-1/311 pQCD3/71/51111 Neutron Wavefunction (Spin and Flavor Symmetric) Nucleon Structure at large x Bj 11 110 )( 3 2 )( 3 1 )( 3 1 )( 18 1 )( 2 1     SS SSS ddu u udd d dn

7. Nucleon Model F 2 n /F 2 p d/u  u/u  d/d A1nA1nA1nA1n A1pA1pA1pA1p SU(6)2/31/22/3-1/305/9 Valence Quark 1/401-1/311 pQCD3/71/51111 Neutron Wavefunction (Spin and Flavor Symmetric) Nucleon Structure at large x Bj 11 110 )( 3 2 )( 3 1 )( 3 1 )( 18 1 )( 2 1     SS SSS ddu u udd d dn

8. Nucleon Model F 2 n /F 2 p d/u  u/u  d/d A1nA1nA1nA1n A1pA1pA1pA1p SU(6)2/31/22/3-1/305/9 Valence Quark 1/401-1/311 pQCD3/71/51111 Neutron Wavefunction (Spin and Flavor Symmetric) Nucleon Structure at large x Bj 11 110 )( 3 2 )( 3 1 )( 3 1 )( 18 1 )( 2 1     SS SSS ddu u udd d dn Suppressed by an extra (1-x) 2

9. pQCD and SU(6) breaking quark models  A1p, A1n 1 as x 1 and large Q2 But the mechanisms are very different CQM – hyperfine interaction between quarks: symmetric configurations suppressed. pQCD – at high x quark carrying the much of the nucleon momentum has the same spin direction as the nucleon: HHC From Close and Melnitchouk

10. pQCD power counting with Lz=1 state included

11. A 1 n versus of Q 2 and x in the valence region role of OAM in the nucleon extraction of higher twist F2=F2=

12. Approved Experiments 6.6 GeV, 8.8 GeV polarized electron beams: 10  A, Pe = 0.8 Hall A polarized 3 He target: 30 cm of useful length. Bigbite Spectrometer @ 30 o HRS-L @ 30 o

13. Using Bigbite with 6.6 GeV and 8.8 GeV beam ~ 500 h Using HMS+SHMS with 11 GeV beam, ~ 1200 h Approved Experiments

14. Projected data: DIS MPS: 75 hours MPS: 25 hours MPS 600 hours @ 40 o

15. DIS Resonance Kinematic Coverage 8.8 Gev beam @ 30 o 6.6 Gev beam @ 30 o 11 Gev beam @ 30 o 11 Gev beam @ 40 o

16. Projected data for the solenoid Solenoid will allow high precision DIS data over a fine grid of Q2 and X: But highest x is still limited to ~ 0.75 as in Bigbite of Super-Bigbite Study Q2 dependence, higher-twist etc.

17. DIS Resonance Kinematic Coverage 8.8 Gev beam @ 30 o 6.6 Gev beam @ 30 o 11 Gev beam @ 30 o 11 Gev beam @ 40 o

18. Projected data for Bigbite in Resonance region: better coverage with solenoid. Solenoid will allow high precision data in Resonance region over a fine grid of Q2 and X: If little or no Q2 dependence -> DIS behavior (duality): can use this resonance data to extract polarized PDFs at very high x

19. DIS Resonance = 1 GeV 2 = 1.7 GeV 2 = 2.6 GeV 2 = 3.6 GeV 2 New A 1 results from Hall A experiment E01-012