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Experimental Study of Duality in SIDIS at JLab

Experimental Study of Duality in SIDIS at JLab. P. Bosted (JLab), for the E00-108 Collaboration. DNP05, September 2005. Semi-inclusive processes Factorization as a test of quark-hadron duality Factorization tests in unpolarized SIDIS. Semi-inclusive DIS. pion.

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Experimental Study of Duality in SIDIS at JLab

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  1. Experimental Study of Duality in SIDIS at JLab P. Bosted (JLab), for the E00-108 Collaboration DNP05, September 2005 • Semi-inclusive processes • Factorization as a test of quark-hadron duality • Factorization tests in unpolarized SIDIS

  2. Semi-inclusive DIS pion Main focus of SIDIS studies: MX • orbital angular momentum of quarks • parton distributions at large x X.Ji • Where region I/II boundary? • Can useful information come from Region II? P. Bosted, DNP05, September 2005

  3. SIDIS kinematic plane and relevant variables P. Bosted, DNP05, September 2005

  4. Missing mass of pions in ep->e’pX p0 D++ p- p+ n D0 Duality question: is MX>1.4 GeV (approximately z<0.7 for Q2-2.5 GeV2, W=2.5 GeV) needed for SIDIS factorization to work? P. Bosted, DNP05, September 2005

  5. EXPERIMENT E00-108 at JLAB • Unpolarized electrons E=6 GeV • Scattered electrons E’=1.6 GeV, 30 deg. • Detected positive and negative pions near 12 degrees • Proton and deuteron targets • Made scans in x,z,pt • Data analysis nearing completion P. Bosted, DNP05, September 2005

  6. Z-Dependence of cross sections Jlab E00-108, Preliminary 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, Q2=2.5 GeV2, W=2.5 GeV P. Bosted, DNP05, September 2005

  7. Unpolarized SIDIS: new test A Simple picture in valence region: sp(p+) = 4u(x)D+(z) + d(x)D-(z) sp(p-) = 4u(x)D-(z) + d(x)D+(z) sd(p+) = [u(x)+d(x)] [4D+(z) + D-(z)] sd(p-) = [u(x)+d(x)] [4D-(z) + D+(z)] Rpd= [sp(p+) + sp(p-)] / [sd(p+) + sd(p-)] = [4u(x) + d(x)] / 5[u(x)+d(x)] = sp(x)/sd(x) Rpd should be independent of z and pt x-dependence of Rpd should be same as inclusive sp(x)/sd(x) P. Bosted, DNP05, September 2005

  8. Unpolarized SIDIS: new test A Rpd is independent of z for 0.4<z<0.7 for W=2.5 GeV, Q2=2.5 GeV2, x=0.3, low pt Good agreement GRV LO (solid curve), NLO (dashed curve, using Lund PEPSI MC) 15% level deviations for z>0.7 (Mx<1.4 GeV) Influence of Delta? Open (closed) circles are without (with) diffractive rho contribution P. Bosted, DNP05, September 2005

  9. Unpolarized SIDIS: new test A Rpd is independent of pt for z=0.55 W=2.5 GeV, Q2=2.5 GeV2, x=0.3 Good agreement GRV98 P. Bosted, DNP05, September 2005

  10. Unpolarized SIDIS: new test A Rpd follows expected x-dependence for z=0.55 W=2.5 GeV, Q2=2.5 GeV2, low pt Pretty good agreement with GRV (using PEPSI MC, solid histogram) P. Bosted, DNP05, September 2005

  11. Unpolarized SIDIS: new test B Simple picture in valence region: sp(p+) = 4u(x)D+(z) + d(x)D-(z) sp(p-) = 4u(x)D-(z) + d(x)D+(z) sd(p+) = [u(x)+d(x)] [4D+(z) + D-(z)] sd(p-) = [u(x)+d(x)] [4D-(z) + D+(z)] Rpd= [sp(p+) - sp(p-)] / [sd(p+) - sd(p-)] = [4uv(x) - dv(x)] / 3[uv(x)+dv(x)] Rpd should be independent of z and pt x-dependence of Rpd should follow PDF predictions P. Bosted, DNP05, September 2005

  12. Unpolarized SIDIS: new test B Rpd is independent of z for 0.4<z<0.7 for W=2.5 GeV, Q2=2.5 GeV2, x=0.3, low pt Good agreement GRV LO (solid curve), NLO (dashed curve, using Lund PEPSI MC) 15% level deviations for z>0.7 (Mx<1.4 GeV) Influence of Delta? P. Bosted, DNP05, September 2005

  13. Unpolarized SIDIS: new test B Rpd is independent of pt for z=0.55 W=2.5 GeV, Q2=2.5 GeV2, x=0.3 Good agreement GRV98 P. Bosted, DNP05, September 2005

  14. Unpolarized SIDIS: new test B Rpd follows expected x-dependence for z=0.55 W=2.5 GeV, Q2=2.5 GeV2, low pt Pretty good agreement with GRV (using PEPSI MC, solid histogram) P. Bosted, DNP05, September 2005

  15. Summary • Factorization tests with both unpolarized SIDIS work surprisingly well for W=2.5 GeV, Q2>2 GeV2, 0.3<z<0.7, pt<0.5 GeV, even for Mx<2 GeV, as long as Mx>1.4 GeV (another evidence of quark-hadron duality) • Breakdown of factorization at high z: may be due to Delta(1232) excitation (diffraction vector meson production does not appear to be as important) • Data may be used even with 6 GeV electrons to study PDFs, at least in limited kinematic region • More data planned all final states at 6 GeV and with 11 GeV at Jlab. High statistical accuracy tests will better quantify the useful kinematic range of SIDIS P. Bosted, DNP05, September 2005

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