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Spin-Flavor Decomposition J. P. Chen, Jefferson Lab PVSA Workshop, April 26-27, 2007, Brookhaven National Lab Polarized Inclusive DIS, u/u and d/d from A 1 n /A 1 p Spin-Flavor decomposition in high-x (valence) region Polarized Semi-Incluisve DIS Spin-Flavor decomposition in moderate-x region Polarized Parity-Violating DIS A new window to study sea quark polarization JLab 12 GeV upgrade and a large acceptance solenoid detector A powerful tool for nucleon spin-flavor decomposition

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Unpolarized and Polarized Structure Functions

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Unpolarized Parton Distributions (CTEQ6) After 40 years DIS experiments, unpolarized structure of the nucleon reasonably well understood. High x valence quark dominating

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NLO Polarized Parton Distributions (AAC06)

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Polarized Inclusive DIS Valence Quark Spin-Flavor decomposition at high x

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World data for A 1 Proton Neutron

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Precision A 1 n at High x from Hall A E99-117 First precision A 1 n data at high x Extracting valence quark spin distributions Test our fundamental understanding of valence quark picture SU(6) symmetry Valence quark models pQCD (with HHC) predictions Quark orbital angular momentum Crucial input for pQCD fit to PDF PRL 92, 012004 (2004) PRC 70, 065207 (2004)

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A 1 p /A 1 d Results from CLAS Proton Deuteron

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Naïve Extraction of Polarized Quark Distributions Combining A 1 n and A 1 p results Valence quark dominating at high x u quark spin as expected d quark spin stays negative! Disagree with pQCD model calculations assuming HHC (hadron helicity conservation) Quark orbital angular momentum Consistent with valence quark models, pQCD PDF fits without HHC constraint, statistic model Consistent with a new model from Feng Yuan et al. including OAM

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A 1 p at 11 GeV Projections for JLab at 11 GeV A 1 n at 11 GeV

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Spin Structure with the Solenoid at JLab 12 GeV Program on spin structure with polarized target(s) and a solenoid highest polarized luminosity: ~10 36 A solenoid with detector package (GEM, Lead-glass+ Cherenkov) large acceptance: ~700 msr for polarized high luminosity and large acceptance Inclusive DIS: improve by a factor of 10-100 A 1 at high-x: 200 hours, high precision parity violating spin structure g 3 /g 5 : first significant measurement SIDIS: improve by a factor of 100-1000 spin-flavor decomposition (~2 orders improvement) transversity and TMDs,

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3 He target Solenoid detector for (SI)DIS GEMs Gas Cerenkov Calorimeter GEMs

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With Standard HMS+SHMS, 1800 hours (X. Zheng) With Solenoid, 200 hours

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Polarized Semi-inclusive DIS Spin-Flavor decomposition at moderate x

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u v and d v at JLab 11 GeV Flavor decomposition with SIDIS With standard HMS+SHMS (see X. Jiang’s Talk) compared with HERMES With Solenoid, 2 orders of magnitude improvement

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Polarized Sea with SIDIS Polarized Sea JLab @11 GeV With standard HMS+SHMS (X. Jiang’s talk) compared with HERMES With Solenoid, 2 orders of magnitude improvement

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Polarized Parity Violating DIS Sea quark polarization

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Longitudinal Target Single Spin Asymmetry Unpolarized beam on longitudinally polarized target keep Z interference terms, neglect Z 2 terms g 1 Z term can be eliminated by using positron beam

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PV-SSF in Naïve Parton Model Naïve Parton Model: Put back into the general formula, we get g 3 provides access to polarized sea quark distributions. Potential access to polarized strange quark distributions.

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Measure PV-TSSA with the Selonoid At x=0.2, Q 2 =2.4, y=0.58, A~ 10 -5 -10 -4 Need high luminosity and large acceptance Rate estimation with the Solenoid detector: 1000 hours beam, statistical precision for asymmetry will be a few x 10 -5. A significant first measurement (~ a few )

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Projection of Collins/Sivers Asymmetries vs P T and x for + (60 days) For one z bin (0.5-0.6) Will obtain 4 z bins (0.3-0.7) Also - at same time With upgraded PID for K+ and K-

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Summary Spin-Flavor decomposition: Polarized inclusive DIS in high-x region Valence quark polarization Polarized semi-inclusive DIS in moderate-x region Valence and sea quark polarization Polarized parity violating DIS A new tool to study sea quark polarization A large acceptance solenoid with high luminosity 700 msr, 10 36 polarized (n) luminosity Improvement of a factor of 10-100 in acceptance*luminosity

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