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Spin and azimuthal asymmetries in SIDIS at JLAB  Physics Motivation  Jlab kinematics and factorization  Double spin asymmetries  Single Spin Asymmetries.

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Presentation on theme: "Spin and azimuthal asymmetries in SIDIS at JLAB  Physics Motivation  Jlab kinematics and factorization  Double spin asymmetries  Single Spin Asymmetries."— Presentation transcript:

1 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

2 P. Bosted, SIR-20052 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

3 P. Bosted, SIR-20053 SIDIS kinematic plane and relevant variables

4 P. Bosted, SIR-20054 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 E00-108 in Hall C

5 P. Bosted, SIR-20055 Hall C E00-108 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

6 P. Bosted, SIR-20056 From E00-108 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 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 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 )

9 P. Bosted, SIR-20059 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

10 P. Bosted, SIR-200510 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

11 P. Bosted, SIR-200511 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  - )

12 P. Bosted, SIR-200512 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 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

14 P. Bosted, SIR-200514 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

15 P. Bosted, SIR-200515 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?)

16 P. Bosted, SIR-200516 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

17 P. Bosted, SIR-200517 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:

18 P. Bosted, SIR-200518 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 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

20 P. Bosted, SIR-200520 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.

21 P. Bosted, SIR-200521 support slides…..

22 P. Bosted, SIR-200522 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 

23 P. Bosted, SIR-200523 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

24 P. Bosted, SIR-200524 A UL SSA: z-dependence CLAS PRELIMINARY

25 P. Bosted, SIR-200525 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  ++

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