Dynamical coupled-channels study of photo- and electro-production reactions Hiroyuki Kamano (Excited Baryon Analysis Center, Jefferson Lab) in collaboration with B. Julia-Diaz, T.-S. H. Lee, A. Matsuyama, T. Sato, N. Suzuki Joint DNP/JPS meeting Oct. 13-17

Outline Excited Baryon Analysis Center (EBAC) @JLab Recent results from EBAC-DCC analysis of ep  e’pN reactions Current work on “Complete Experiment” of pseudoscalar meson photoproduction reactions

Excited Baryon Analysis Center @ Jefferson Lab Founded in January 2006 http://ebac-theory.jlab.org/ Reaction Data Objectives and goals: Through the comprehensive analysis of world data of pN, gN, N(e,e’) reactions, Determine N* spectrum (masses, widths) Extract N* form factors, in particular the N-N* electromagnetic transition form factors Provide reaction mechanism information for interpreting the N* parameters Dynamical Coupled-Channels Analysis @ EBAC N* parameters Hadron Models Lattice QCD QCD

Dynamical coupled-channels model @ EBAC For details see Matsuyama, Sato, Lee, Phys. Rep. 439,193 (2007) Partial wave (LSJ) amplitude of a  b reaction: Reaction channels: Potential: coupled-channels effect ground meson-baryon exchange bare N* state

Single pion electroproduction (Q2 > 0) Julia-Diaz, Kamano, Lee, Matsuyama, Sato, Suzuki, PRC80 025207 (2009) Fit to the structure function data from CLAS p (e,e’ p0) p Fit is performed in W < 1.6 GeV Q2 < 1.5 (GeV/c)2 is determined at each Q2.

gamma* N  Delta(1232) form factors Full results × Other analysis Meson cloud

“Complete Experiment” of pseudoscalar meson photoproduction reactions Measure ALL polarization observables needed to determine amplitudes (up to overall phase) “Complete Experiment” = unpolarized diff. crs. sec. single spin beam-target beam-recoil target-recoil 8 /16 observables needed! Chiang, Tabakin PRC55 2054 (1997) How much critical are the polarization observables on constraining reaction models and extracting N* parameters ? Measurement of gN  KY pol. obs. is very active. OVER-COMPLETE experiment planned by CLAS for g p  K+ Y, g n  KY. Provides critical information on N*  KY decays !!

Comparison of all gN  pN observables Hoblit, Kamano, Lee, Sandorfi, in preparation EBAC SAID MAID

Polarization observables of K+ Lambda photoproduction Hoblit, Kamano, Lee, Sandorfi, in preparation Amplitudes from KY model by Julia-Diaz, Saghai, Lee, Tabakin PRC73 055204 (2006) The pN, gN  KY data before 2006 are used for the model construction Necessity of new N* states for explaining the data: D13, S11, P13 with mass 1800-1950 MeV

Summary Presented our recent analysis of ep  e’pN reaction. Examined significance of the polarization observables for construction of reaction models and extraction of N* parameters. Our model successfully describes the reaction at Q2 < 1.5 (GeV/c)2. N-N* e.m. transition form factors are extracted for the N* states up to the second resonance region. gp  pN reaction: Provides useful information on constraining reaction models beyond the D(1232). gp  KY reaction: Will be crucial for extracting N*  KY information including recently suggested new N* states around 1.9 GeV.

Back up

Availability of structure function data at Q2 < 1.5 (GeV/c)2

Dynamical coupled-channels model @ EBAC For details see Matsuyama, Sato, Lee, Phys. Rep. 439,193 (2007) coupled-channels effect

Current status of the EBAC-DCC analysis Hadronic part p N  p N : fitted to the SAID PWA up to W = 2 GeV. Julia-Diaz, Lee, Matsuyama, Sato, PRC76 065201 (2007) p N  p p N : cross sections calculated with the pN model; fit is ongoing. Kamano, Julia-Diaz, Lee, Matsuyama, Sato, PRC79 025206 (2009) p N  h N : fitted to the data up to W = 2 GeV Durand, Julia-Diaz, Lee, Saghai, Sato, PRC78 025204 (2008) g(*) N  p N : fitted to the data up to W = 1.6 GeV (and up to Q2 = 1.5 GeV2) (photoproduction) Julia-Diaz, Lee, Matsuyama, Sato, Smith, PRC77 045205 (2008) (electroproduction) Julia-Diaz, Kamano, Lee, Matsuyama, Sato, Suzuki, PRC80 025207 (2009) g N  p p N : cross sections calculated with the gN & pN model; fit is ongoing. Kamano, Julia-Diaz, Lee, Matsuyama, Sato, arXiv:0909.1129 [nucl-th] g(*) N  h N : in progress g N  K L : in progress Electromagnetic part