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Semi-Inclusive DIS measurements at Jefferson Lab

Semi-Inclusive DIS measurements at Jefferson Lab. P. Bosted for the E00-108 Collaboration (presented by B. Sawatzky). DNP, October 2009. Semi-inclusive DIS. pion. Main focus of SIDIS studies:. M X. orbital motion of quarks (p t , f dependence)

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Semi-Inclusive DIS measurements at Jefferson Lab

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  1. Semi-Inclusive DIS measurements at Jefferson Lab P. Bosted for the E00-108 Collaboration (presented by B. Sawatzky) DNP, October 2009

  2. Semi-inclusive DIS pion Main focus of SIDIS studies: MX • orbital motion of quarks (pt, f dependence) • parton distributions (separate valence, sea) X.Ji • Where region I/II boundary? • Can useful information come from Region II?

  3. SIDIS kinematic plane and relevant variables pion MX Pt is transverse momentum relative to virtual photon W2=M2+Q2(1/x-1) is invariant mass of total hadronic final state

  4. Hall C experiment E00-108 • Electron beam with E=5.5 GeV • Proton and Deuteron targets • SIDIS measurements of both p+ and p- • Electrons scattered at 24 to 36 degrees into SOS • Pions detected in the HMS spectrometer • Scan of z at fixed Pt=0, x=0.3 • Scan of x at fixed Pt=0, z=0.55 • Scan of Pt at fixed x=0.3, Pt=0 • Rather low W: 2<W<3 GeV • Rather low Mx: will description in terms of scattering of single quarks hold?

  5. Z-Dependence of cross sections Good agreement with prediction using CTEQ5M PDFs and Binnewies fragmentation functions, except for z>0.7, or Mx<1.4 GeV. D or D+,D- Jlab Hall C X=0.3, Q2=2.5 GeV2, W=2.5 GeV

  6. How Can We Verify Factorization? • Neglect sea quarks and assume no pt dependence to parton distribution functions • Fragmentation function dependence drops out in Leading Order [sp(p+) + sp(p-)]/[sd(p+) + sd(p-)] = [4u(x) + d(x)]/[5(u(x) + d(x))] ~ sp/sd independent of z and pt [sp(p+) - sp(p-)]/[sd(p+) - sd(p-)] = [4u(x) - d(x)]/[3(u(x) + d(x))] independent of z and pt, but more sensitive to assumptions

  7. Duality in Pion Electroproduction ... or Why does factorization appear to work well at low energies … GRV & CTEQ, @ LO or NLO “Works” better (recall, z = 0.65 ~ Mx2 = 2.5 GeV2) “Works” worse Closed (open) symbols reflect data after (before) events from coherent r production are subtracted

  8. More general (e,e’h) “SIDIS” framework General formalism for (e,e’h) coincidence reaction: Factorized formalism for SIDIS (e,e’h): In general, A and B are functions of (x,Q2,z,pT,f). Note: typical assumption is that that sL/sT = RDIS Determination of the pT and f dependencies are interesting in their own right  potential to determine the transverse momentum distributions of quarks.

  9. kT-dependent SIDIS m p x TMD Schematic diagram of semi-inclusive pion electroproduction with a factorized QCD quark parton model at lowest order in as. Final transverse momentum of the detected pion Pt arises from convolution of the struck quark transverse momentum kt with the transverse momentum generated during the fragmentation pt. TMDu(x,kT) f1,g1,f1T ,g1T h1, h1T ,h1L ,h1 pt= Pt– zkt+ O(kt2/Q2) Linked to framework of Transverse Momentum Dependent Parton Distributions

  10. Transverse momentum dependence of SIDIS Pt dependence very similar for proton and deuterium targets, but deuterium slopes systematically smaller?

  11. Transverse momentum dependence of SIDIS Fit to updated version of data of previous slide With severn parameter fit: important four are: (m+)2 ~ width of D+(z,pt), (m-)2 ~ width of D-(z,pt), (mu)2 ~ width of u(x,kt), (md)2 ~ width of d(x,kt) Assumptions: • Factorization valid • Fragmentation functions do not depend on quark flavor, • Transverse momentum widths of quark and fragmentation functions are gaussian and can be added in quadrature • Sea quarks are negligible • Particular function form for the Cahn effect • No additional higher twist effects • NLO corrections can be ignored

  12. Transverse momentum dependence of SIDIS + vs u - vs d d vs u - vs + • Ellipses are fits with different systematic assumptions • Black dot is from a particular di-quark model • Dashed lines have equal (u,d) or (+,-) widths

  13. Summary and Outlook • All widths of expected order-or-magnitude (I.e. 0.1 to 0.2 GeV2) • d-quark width may be smaller than u-quark width • Technique seems promising for future studies. • Huge increase in kinematic reach and statistical accuracy expected with JLab upgrade to 11 GeV. • Proposal E09-017 plans to continue these studies at higher W, Q2 and Mx over a wide region of x and z.

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