1. Kijun Park Univ. of South Carolina Kijun Park Univ. of South Carolina Aug. 30, 2008 Hadron Spectroscopy Physics Working Group Meeting Electroproduction of soft pions at high Q 2 from CLAS DNP

2. Historically, threshold pion in the photo- and electroproduction is the very old subject that has been receiving continuous attention from both experiment and theory sides for many years. Pion mass vanishing approximation in Chiral Symmetry allows us to make an exact prediction for threshold cross section known as LET The LET established the connection between charged pion electroproduction and axial form factor in nucleon. Therefore, It is very interesting to extracting Axial Form Factor which is dominated by S- wave transverse multipole E 0+ in LCSR Historically, threshold pion in the photo- and electroproduction is the very old subject that has been receiving continuous attention from both experiment and theory sides for many years. Pion mass vanishing approximation in Chiral Symmetry allows us to make an exact prediction for threshold cross section known as LET The LET established the connection between charged pion electroproduction and axial form factor in nucleon. Therefore, It is very interesting to extracting Axial Form Factor which is dominated by S- wave transverse multipole E 0+ in LCSR HSPW Meeting Aug. 30, 2008 K. Park DNP

3. Perspective of soft pion in terms of Q 2 at threshold Low-Energy Theorem (LET) for Q 2 =0 Restriction to the charged pion Chi ral symmetry + current algebra for electroproduction Re-derived LETs Current algebra + PCAC Chi ral perturbation theory pQCD factorization methods 1954 1960s 1970s Kroll-Ruderman Nambu, Laurie, Schrauner Vainshtein, Zakharov 1990s Scherer, Koch Brodsky, Lepage, Efremov, Radyunshkin, Pobylitsa, Polyakov, Strikman, et al HSPW Meeting Aug. 30, 2008 K. Park DNP

4. Correlation Function Light Cone Sum Rule V. M. Braun, PRD77 (2008) Light Corn Sum Rule Reproduce LET for Q 2 ~ 1GeV 2 Reproduce pQCD for Q 2 →∞ 2007 V. Braun Extended for near pion threshold regions HSPW Meeting Aug. 30, 2008 K. Park DNP

5. Differential Cross Section Only S-wave contribution HSPW Meeting Aug. 30, 2008 K. Park DNP

6. Legendre moments vs. Multipoles Structure Functions vs. Legendre moments Partial Wave Series with Legendre Polynomials from S.F. sensitive ! insensitive ! HSPW Meeting Aug. 30, 2008 K. Park DNP

7. Legendre moments vs. Form Factors V.Braun PRD 77(2008) HSPW Meeting Aug. 30, 2008 K. Park DNP

8. VariableUnitRange# BinWidth Q2Q2 GeV 2 2.05 ~ 4.165various WGeV 1.11 ~ 1.1530.02 cosθ * π -1.0~ 1.0100.2 φ *πφ *π Deg. 0. ~ 360.1230 Kinematical Coverage * E=5.754GeV, LH2 target (unpol.) * Oct. 2001-Jan. 2002 HSPW Meeting Aug. 30, 2008 K. Park DNP

9. Cross check acceptance calculation - based on phase space event generator - compare between GENEV and AAO Re-calculation of radiative correction - based on new binning (12 φ ) from ExcluRad Study of ExcluRad model dependence - MAID2003 vs. Sato-Lee 2004 Apply more tight physics cuts - electron, pion fiducial cuts Study of systematic uncertainties Cross check acceptance calculation - based on phase space event generator - compare between GENEV and AAO Re-calculation of radiative correction - based on new binning (12 φ ) from ExcluRad Study of ExcluRad model dependence - MAID2003 vs. Sato-Lee 2004 Apply more tight physics cuts - electron, pion fiducial cuts Study of systematic uncertainties Analysis -Details HSPW Meeting Aug. 30, 2008 K. Park

10. Analysis -Details RC difference is less than few % in nπ + channel !! HSPW Meeting Aug. 30, 2008 K. Park

11. Cross Section ( φ* ) φ* – dependent cross section in term of W, Q 2, cosθ* Various physics models Preliminary Results Blue shade : systematic uncertainty estimation Red data : CRS with new analysis Preliminary HSPW Meeting Aug. 30, 2008 K. Park DNP

12. Structure Function insensitive ! sensitive ! Preliminary HSPW Meeting Aug. 30, 2008 K. Park DNP

13. Structure Function sensitive ! Preliminary sensitive ! HSPW Meeting Aug. 30, 2008 K. Park DNP

14. Legendre Moments HSPW Meeting Aug. 30, 2008 K. Park DNP

15. l-moments vs. F. F. for n π + channel Due to low-energy theorem(LET) relates the S-wave multipoles or equivalently, the form factor G 1, G 2 @ threshold P.E. Bosted Phys. Rev. C 51 (1995) P.E. Bosted Phys. Rev. C 51 (1995) Scherer, Koch, NPA534(1991) Vainshtein, Zakharov NPB36(1972) Scherer, Koch, NPA534(1991) Vainshtein, Zakharov NPB36(1972) Assumption in LCSR V.Braun PRD77(2008) Assumption in LCSR V.Braun PRD77(2008) HSPW Meeting Aug. 30, 2008 K. Park DNP

16. Legendre moments vs. Form Factors HSPW Meeting Aug. 30, 2008 K. Park DNP

17. Legendre moments vs. Form Factors HSPW Meeting Aug. 30, 2008 K. Park DNP

18. Lines : MAID07 Bold : Real Thin : Imaginary Q 2 dependence of the Normalized E 0+ Multipole by dipole Preliminary Color index HSPW Meeting Aug. 30, 2008 K. Park DNP

19. Due to low-energy theorem(LET) relates the S-wave multipoles or equivalently, the form factor G 1, G 2 @ threshold P.E. Bosted Phys. Rev. C 51 (1995) P.E. Bosted Phys. Rev. C 51 (1995) P.E. Bosted Phys. Rev. C 51 (1995) P.E. Bosted Phys. Rev. C 51 (1995) l-moments vs. F. F. for n π + channel HSPW Meeting Aug. 30, 2008 K. Park

20. l-moments vs. F. F. HSPW Meeting Aug. 30, 2008 K. Park

21. * Real parts x1, x2 can be determined by A1, D0 legendre coeff. * 3 Eqs. 4 parameter should be determined * Imaginary parts y1, y2 can be determined in 2cases * Asymmetry helps to determine complete form factor Legendre moments vs. Form Factors HSPW Meeting Aug. 30, 2008 K. Park

22. Assumption of G E n =0 Assumption of Im(G 2 )=y 2 =0 Q 2 dependence of the Normalized E 0+ Multipole by dipole Preliminary Color index HSPW Meeting Aug. 30, 2008 K. Park

23. Complete Cross check acceptance calculation - based on different simulation - applying different cuts Verification of model independent radiative correction Extract new cross sections based on above Extract very preliminary E 0+ /G D for nπ + channel Calculate the systematic errors is much easier extraction than in the nπ + channel E 0+ multipole is stronger dominance than L 0+ Still ….. Double check by communication with theories Implement asymmetry data Complete Cross check acceptance calculation - based on different simulation - applying different cuts Verification of model independent radiative correction Extract new cross sections based on above Extract very preliminary E 0+ /G D for nπ + channel Calculate the systematic errors is much easier extraction than in the nπ + channel E 0+ multipole is stronger dominance than L 0+ Still ….. Double check by communication with theories Implement asymmetry data Summary and Future plans HSPW Meeting Aug. 30, 2008 K. Park DNP

24. Thank you for your attention !

25. LCSR- based model for the Q 2 dependence of the electric, longitudinal Partial Waves at threshold [GeV -1 ] MAID07 Arnt et al. HSPW Meeting Aug. 30, 2008 K. Park

26. MAID2007 Bold –Real part Thin – Imaginary part HSPW Meeting Aug. 30, 2008 K. Park

27. Bold –Real part Thin – Imaginary part MAID2007 HSPW Meeting Aug. 30, 2008 K. Park

28. Threshold Pion Production @ Workshop, Jlab Feb. 19, 2008 V. M. Braun HSPW Meeting Aug. 30, 2008 K. Park

29. Neutron Magnetic Structure Preliminary HSPW Meeting Aug. 30, 2008 K. Park

30. Constructed relating the amplitude for the radiative decay of Σ +(p γ ) to properties of the QCD vacuum in alternating magnetic field. An advantage of study because soft contribution to hadron form factor can be calculated in terms of DA’s that enter pQCD calculation without other nonperturbative parameters. New technique : the expansion of the standard QCD sum rule approach to hadron properties in alternating external fields. Constructed relating the amplitude for the radiative decay of Σ +(p γ ) to properties of the QCD vacuum in alternating magnetic field. An advantage of study because soft contribution to hadron form factor can be calculated in terms of DA’s that enter pQCD calculation without other nonperturbative parameters. New technique : the expansion of the standard QCD sum rule approach to hadron properties in alternating external fields. LCSR[Light Cone Sum Rule] HSPW Meeting Aug. 30, 2008 K. Park

31. Q 2 dependence of the Normalized E 0+ Multipole by dipole Preliminary HSPW Meeting Aug. 30, 2008 K. Park

32. Kijun Park Univ. of South Carolina Kijun Park Univ. of South Carolina Aug. 30, 2008 Hadron Spectroscopy Physics Working Group Meeting Electroproduction of soft pions at high Q 2 from CLAS DNP