Spin and azimuthal asymmetries in SIDIS at JLAB  Physics Motivation  Jlab kinematics and factorization  Double spin asymmetries  Single Spin Asymmetries  Future measurements  Summary P. Bosted * * In collaboration with H. Avakian, V.Burkert and L.Elouadrhiri SIR-2005 Jefferson Lab

P. Bosted, SIR 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, This talk 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) This talk

P. Bosted, SIR SIDIS kinematic plane and relevant variables

P. Bosted, SIR JLab Kinematics and Facorization  Traditional DIS: W>2 GeV, Q 2 >1.1 GeV 2  Berger criteriium for current fragmentation dominance is z>0.4  Require z<0.7 to avoid diffractive rho meson contributions (and keep M x >1.4 GeV)  Pt<1 GeV (approximately exponential region)  Study if factorization broken for these cuts using unpolarized data from E in Hall C

P. Bosted, SIR Hall C E data Experiment ran in August 2003  Close-to-final data analysis  Small Q 2 variation not corrected yet No visual “bumps and valleys” in pion ratios off deuterium x = 0.32 PRELIMINARY

P. Bosted, SIR From E deuterium data: D - /D + = (4 – N  + /N  - )/(4N  + /N  - - 1)  D - /D + ratio should be independent of x, and data supports this for W=2.5 GeV, Q 2 =2.5 GeV 2, p t <0.3 GeV  but should depend on z  Find similar slope versus z as HERMES, but slightly larger values (could be due to lower average photon energy) z = 0.55 x = 0.32 PRELIMINARY

7 CLAS Experiment Setup and Kinematics Scattering of 5.7 GeV polarized electrons off polarized NH 3, ND 3  ~8M  + in SIDIS kinematics x x

8 Target polarization P T about 0.7 (0.3) for NH 3 (ND 3 ) Beam polarization P B about 0.7 Dilution factor f varies from 0.1 to 0.3: used Lund model for n/p ratio and preliminary Hall B data for A-dependence Depolarization factor D LL (y) evaluated assuming R same as for inclusive. Assumed A perp =0 (not measured) No radiative corrections applied “  + ” and “  - ” include some K +, K - for P>1.5 GeV  0 events cleanly identified with two photons Determination of g 1 /F 1 (approximately A 1 )

P. Bosted, SIR x-depenence of SIDIS g 1 /F 1 Good agreement with HERMES  + data at 3x higher Q 2 x-dependence follows PEPSI (Lund) Monte Carlo using GRSV polarized PDFs (LO) Magnitude also in good agreement with simulation

P. Bosted, SIR SIDIS: factorization studies g 1 /F 1 inclusive, for the sum of     , and for   are consistent with each other in the range 0.4<z<0.7, as expected in LO with factorization and current fragmentation dominance GRVS

P. Bosted, SIR z-depenence of SIDIS g 1 /F 1 CLAS 5.7 GeV PRELIMINARY No significant z-dependence seen 0.3<z<0.7, as expected for factorization and current fragmentation dominance Good agreement with PEPSI predictions (including dropoff at high z for  - )

P. Bosted, SIR p t -depenence of SIDIS g 1 /F 1 No p t dependence expected in LO if current fragmentation dominance and factorization Slight p t dependence seen (but results quite sensitive to p t dependence of A-dependence needed for dilution factor) Reasonable agreement with PEPSI predictions. PRELIMINARY CLAS 5.7 GeV

13 SIDIS g 1 /F 1 for Deuteron Results don’t agree as well with PEPSI using GRSV, more sensitive to un-favored fragmentation function and NLO corrections than proton (although errors are about a factor of two larger) NLO QCD fits including new SIDIS CLAS data can help constrain polarized PDFs in valence region PRELIMINARY CLAS 5.7 GeV

P. Bosted, SIR Longitudinally Polarized Target SSA  Clear   dependence seen for proton target and  +,  0  Fit A*sin(  ) + B*sin(2  ) for Twist-3 and Twist-2 respectively

P. Bosted, SIR SSA: x-dependence PRELIMINARY 5.7 GeV Twist-2 Higher Twist Data in rough agreement with Efremov et al. predictions, except for  0 sin(  ) term (evidence for terms not involving Collins fragmentation?)

P. Bosted, SIR For Collins fragmentation function use HERMES data 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 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

P. Bosted, SIR Future: more  0 data in SIDIS 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:

P. Bosted, SIR 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

19  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 curves,  QSM from Efremov et al

P. Bosted, SIR 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: may be used in future NLO QCD fits. sin  and  sin2  SSA measured, providing access to the twist-2 TMD h 1L distribution and testing the Collins fragmentation function Future measurements with IC, if approved, will greatly improve  0 data. Much greater improvements for all reactions possible with 12 GeV upgrade due to much larger coverage of DIS kinematics.

P. Bosted, SIR support slides…..

P. Bosted, SIR 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 

P. Bosted, SIR 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

P. Bosted, SIR A UL SSA: z-dependence CLAS PRELIMINARY

P. Bosted, SIR 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  ++