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

P. Bosted, DNP h Single pion production in hard scattering Target fragmentation Current fragmentation Fracture Functions xFxF M 0 1 h h PDF GPD k T -dependent PDFsGeneralized PDFs Wide kinematic coverage of large acceptance detectors allows studies of hadronization both in the target and current fragmentation regions x F - momentum in the CM frame x F >0 (current fragmentation) PDF h x F <0 (target fragmentation) h

P. Bosted, DNP Polarized Semi-Inclusive DIS Cross section is a function of scale variables x,y,z Parton-Hadron transition: by fragmentation function D  +(  ( z ): probability for a u-quark to produce a  + (  - ) with momentum fraction z Hadron-Parton transition: by distribution function f 1 u ( x ): probability to find a u-quark with a momentum fraction x 1u = E-E’ y = /E x = Q 2 /2M z = E h / z

P. Bosted, DNP Transverse momentum of quarks To study orbital motion of quarks in semi-inclusive DIS measurements in a wide range of x,z,P T,  are required. k T – led to introduction of k T dependent PDFs (TMDs) k T – crucial for orbital momentum and spin structure studies –led to SSA in hard scattering processes k T - important for cross section description - P T distributions of hadrons in DIS - exclusive photon production (DVCS) - hard exclusive vector meson cross section - pp →  0 X (E704,RHIC) cross sections Spin-Azimuthal Asymmetries: sensitive to k T

P. Bosted, DNP SIDIS (  *p→  X) cross section at leading twist (Ji et al.) structure functions = pdf × fragm × hard × soft (all universal) e Unpolarized target Longitudinally pol. target Transversely pol. target e e p p Off diagonal PDFs related to interference between L=0 and L=1 light-cone wave functions. Boer-Mulders 1998 Kotzinian-Mulders 1996 Collins-1993 To observe the transverse polarization of quarks in SIDIS spin dependent fragmentation is required!

P. Bosted, DNP 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, DNP Z-Dependence of unpolarized cross sections Pretty good agreement with prediction using CTEQ5M PDFs and Binnewies fragmentation functions, except for z>0.7, or Mx>1.4 GeV. X=0.3, Q 2 =2.5 GeV 2, W=2.5 GeV Jlab E00-108, Preliminary, E=5.5 GeV

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

P. Bosted, DNP 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, probably small) No radiative corrections applied (expected to be small) “  + ” and “  - ” include some K +, K - for P>1.5 GeV  0 events cleanly identified with two photons Experimental Overview

P. Bosted, DNP SIDIS: factorization studies g 1 /F 1 inclusive, for the sum of     , and for   are consistent with each other in the range GeV support this. GRVS

P. Bosted, DNP 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, DNP 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, DNP Significant SSA measured for pions with longitudinally polarized target Complete azimuthal coverage crucial separation of sin  sin2  moments SSA measurements at CLAS p 1 sin  +p 2 sin2  0.12<x<0.48 Q 2 >1.1 GeV 2 P T <1 GeV ep→e’  X W 2 >4 GeV 2 0.4<z<0.7 M X >1.4 GeV y<0.85 CLAS PRELIMINARY p 1 = 0.059±0.010 p 2 =-0.041±0.010 p 1 =-0.042±0.015 p 2 =-0.052±0.016 p 1 =0.082±0.018 p 2 =0.012±0.019

P. Bosted, DNP 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, DNP 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: analysis in progress. Distribution functions from  QSM from Efremov et al

P. Bosted, DNP 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, DNP Higher Twist SSAs Target sin  SSA (Bacchetta et al ) Beam sin  SSA In jet SIDIS only contributions ~ D 1 survive Discussed as main sources of SSA due to the Collins fragmentation With H 1 ┴ (  0 )≈0 (or measured) Target and Beam SSA can be a valuable source of info on HT T-odd distribution functions

P. Bosted, DNP 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, DNP 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

P. Bosted, DNP  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, DNP CLAS12 High luminosity polarized (~80%) CW beam Wide physics acceptance (exclusive, semi-inclusive current and target fragmentation) Wide geometric acceptance 12GeV significantly increase the kinematic acceptance (x10 lumi)

P. Bosted, DNP 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 will greatly improve  0 data, and charged pions too. Much greater improvements for all reactions possible with 12 GeV upgrade due to much larger coverage of DIS kinematics.

P. Bosted, DNP support slides…..

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

P. Bosted, DNP 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  ++

P. Bosted, DNP Collinear Fragmentation  quark The only fragmentation function at leading twist for pions in eN→e’  X is D 1 (z) E e =5.7 GeV No significant variation observed in z distributions of  + for different x ranges ( ) and for A1p as a function of P T

P. Bosted, DNP SIDIS: factorization studies JLab data at 6GeV are consistent with factorization and partonic description for variety of ratio observables P.Bosted

P. Bosted, DNP Collins Effect: azimuthal modulation of the fragmentation function D(z,P T )=D 1 (z,P T )+H 1 ┴(z,P T ) sin(  h  S’ ) spin of quark flips wrt y-axis  S’ =  -  S sin(  h  S ) CC SS STST y x hh PTPT sTsT  S’ CC F UT ∞h 1 H 1 ┴  S’ =  -  S =  -  h SS y x hh PTPT sTsT  S’ CC s T (p×k T )↔ h 1 ┴ F UU ∞h 1 ┴ H 1 ┴  S =  +  h s T (q×P T )↔ H 1 ┴ sin(2  h )  S’ =  -  S =  -  h x CC sin(2  h ) sTsT PTPT hh CC S=hS=h y F UL ∞h 1L H 1 ┴ ┴ (s T k T )(pS L )↔ h 1L ┴ sin  C =sin(  h  S’ ) cos(2  h )

P. Bosted, DNP Flavor decomposition of T-odd f┴ With SSA measurements for      and   on neutron and proton (     ) assuming H fav = H u→  + ≈ -H u→  - =- H unfav In jet SIDIS with massless quarks contributions from H 1 ┴ vanish gauge link contribution L With H 1 ┴ (  0 )≈0 (or measured) target and beam HT SSAs can be a valuable source of info on HT T-odd distribution functions

P. Bosted, DNP 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 