1. New results on SIDIS SSA from JLab  Physics Motivation  Double spin asymmetries  Single Spin Asymmetries  Future measurements  Summary H. Avakian * * In collaboration with P.Bosted, V.Burkert and L.Elouadrhiri DIS-2005 Apr 28 Jefferson Lab

2. Semi-Inclusive Deep Inelastic Scattering (SIDIS): Probes orbital motion of quarks through quark transverse momentum distribution Access to new PDFs not accessible in inclusive DIS. k T -dependent parton distributions Sivers transversity Mulders Off-diagonal PDFs vanish if quarks only in s-state! In addition T-odd PDFs require FSI (Brodsky et al., Collins, Ji et al. 2002)  Factorization of k T -dependent PDFs proven at low P T of hadrons (Ji et al)  Universality of k T -dependent distribution and fragmentation functions proven (Collins,Mets…)

3. H. Avakian, DIS-20053 SIDIS kinematic plane and relevant variables

4. H. Avakian, DIS-20054 The CLAS Detector Scattering of 5.7 GeV polarized electrons off polarized NH 3  ~8M  + in DIS kinematics,SIDIS Q 2 >1.1GeV 2, W 2 >4GeV 2, y<0.85,  beam polarization 73%  target polarization 72% (f=0.2) x x

5. A 1 p -kinematic dependence for  +/-/0 CLAS 5.7 GeV A1pA1p A1pA1p No significant z-dependence of A 1 in the range 0.4<z<0.7 (     ) x dependence of CLAS A 1 p (A ┴ =0) consistent with HERMES data at 3 times higher Q 2 and with PEPSI (LUND)MC. CLAS PRELIMINARY

6. H. Avakian, DIS-20056 SIDIS: factorization studies A 1 inclusive, from      sum and   are consistent (in range 0.4<z<0.7 ) A 1 p dependence can serve an important check of HT effects and applicability of simple partonic description. There is an indication that  A 1 p of   +    is lower than inclusive at large z. GRVS A1+-A1+-

7. H. Avakian, DIS-20057 Longitudinally polarized Target SSA Measure the k T dependent twist-2 distribution and provides an independent test of the Collins fragmentation. Real part of interfe- rence of wave functions with L=0 and L=1  UL ~ KM

8. 8 Study the Collins fragmentation mechanism with long. polarized target For  - and  0 SSA is sensitive to unfavored fragmentation SSA: x-dependence HT–SSA significant for  + and  0 (non-Collins?) A UL (  0 ) ~ H 1 favore +H 1 unfavored PRELIMINARY 5.7 GeV

9. For Collins fragmentation use chirally invariant Manohar-Georgi model (Bacchetta et al) Systematic error only from unknown ratio of favored and unfavored Collins functions (R= H 1 d→  /H 1 u→  ), band correspond to -2.5<R<0  - and  0 SSA will also give access to h 1L d ( If R ≈ -1 deuteron data could be crucial) CLAS-5.7GeV First glimpse of Twist-2 TMD h 1L ┴ PRELIMINARY More data required with  - &  0 Exclusive 2 pion background may be important Distribution functions from  QSM from Efremov et al

10. H. Avakian, DIS-200510  0 in Semi-inclusive DIS 1)SIDIS  0 production is not contaminated by diffractive  2)HT effects and exclusive  0 suppressed 3)Simple PID by  0 -mass (no Kaon contamination) 4)Provides complementary to  +/- information on PDFs disadvantages: reconstruction efficiency (requires detection of 2  ) advantages:

11. H. Avakian, DIS-200511 CLAS+Inner Calorimeter (IC) IC at CLAS opens new avenue for studies of spin and azimuthal asymmetries of exclusive and semi-inclusive     CLAS CLAS+IC CLAS IC 424 PbWO4 ……..crystals Reconstruction efficiency of high energy  0 with IC increases ~ 4 times due to small angle coverage IC  E /E=0.0034/E+0.038/√E+0.022

12. 12  UL ~ KM Longitudinally polarized target SSA using CLAS+IC Provide measurement of SSA for all 3 pions, extract the Mulders TMD and study Collins fragmentation with longitudinally polarized target Allows also measurements of 2 pion asymmetries H unf =-1.2H fav H unf =-5H fav H unf =0 50 days of CLAS+IC (5.7GeV) curves,  QSM from Efremov et al

13. H. Avakian, DIS-200513 Summary Spin and azimuthal asymmetries measured at 5.7 GeV with longitudinally polarized target. Double spin asymmetries of pions are consistent with factorization and partonic picture sin  and  sin2  SSA measured, providing access to the twist-2 TMD h 1L distribution and testing the Collins fragmentation Studies of spin and azimuthal asymmetries at CLAS will significantly improve the error bars for charged pions and will provide a superior measurements with neutral pions allowing precision measurement of the twist-2 k T -dependent PDF.

14. H. Avakian, DIS-200514 support slides…..

15. H. Avakian, DIS-200515 Longitudinally Pol Target: SSA for  + sin2  moment (Kotzinian-Mulders asymmetry) is a clean source of Collins SSA P 1 = 0.0110±0.0024 P 2 =-0.0065±0.0025 Significant sin2  term in the long.pol. x-section compared to A LU

16. H. Avakian, DIS-200516 Collins effect and 2 pion production Simple string fragmentation (Artru model) Sub-leading pion opposite to leading (into page) L=1  production may produce an opposite sign A UT Leading  opposite to leading  (into page) Understanding of 2 pion asymmetries will help to understand single pion mesurements ++ 00 

17. H. Avakian, DIS-200517 sin  SSA  + increases with PT and is consistent with HERMES measurement. A UL SSA: P T -dependence HT –SSA significant for  + and  0 CLAS PRELIMINARY

18. H. Avakian, DIS-200518 sin  SSA  + increases with PT and is consistent with HERMES measurement. A UL SSA: z-dependence HT –SSA significant for  + and  0 CLAS PRELIMINARY

19. H. Avakian, DIS-200519 Longitudinally polarized target+IC:  + Reconstruction efficiency with IC decreases ~ 40%

20. H. Avakian, DIS-200520 Longitudinally polarized target+IC:  - Reconstruction efficiency with IC decreases ~ 10%

21. H. Avakian, DIS-200521 Exclusive  + production Exclusive  +n separated by invariant and missing masses. n ++ e - p  e - n  + π+π0π+π0 Provide access to different combinations of orbital momentum contributions J u,J d   -> 2J u + J d    -> J u - J d Significant transverse target SSA predicted for exclusive   accesible with long.pol. Target with effective polarization ~20% CLAS 5.7 GeV

22. H. Avakian, DIS-200522 Missing mass of pions in ep→e’  X In accessible kinematics (Q 2 >1.5,W 2 >4) low M X (large z) for  0 are suppressed by current CLAS acceptance. -- 00 ++ n 00  ++

23. H. Avakian, DIS-200523 SIDIS: factorization studies A 1 inclusive, from      sum and   are consistent (in range 0.4<z<0.7 ) A 1 p dependence can serve an important check of HT effects and applicability of simple partonic description. There is an indication that  A 1 p of   +    is lower than inclusive at large z. A 1   +  A 1  - ___________ 1+   from-MC GRVS A1+-=A1+-=