1. 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

2. 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

3. Excited Baryon Analysis Center @ Jefferson Lab
Founded in January 2006
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 EBAC
N* parameters
Hadron Models
Lattice QCD
QCD

4. 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

5. Single pion electroproduction (Q2 > 0)
Julia-Diaz, Kamano, Lee, Matsuyama, Sato, Suzuki, PRC (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.

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

7. “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 PRC (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 !!

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

9. Polarization observables of K+ Lambda photoproduction
Hoblit, Kamano, Lee, Sandorfi, in preparation
Amplitudes from KY model by Julia-Diaz, Saghai, Lee, Tabakin PRC (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
MeV

10. 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.

11. Back up

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

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

14. 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, PRC (2007)
p N  p p N : cross sections calculated with the pN model; fit is ongoing.
Kamano, Julia-Diaz, Lee, Matsuyama, Sato, PRC (2009)
p N  h N : fitted to the data up to W = 2 GeV
Durand, Julia-Diaz, Lee, Saghai, Sato, PRC (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, PRC (2008)
(electroproduction) Julia-Diaz, Kamano, Lee, Matsuyama, Sato, Suzuki, PRC (2009)
g N  p p N : cross sections calculated with the gN & pN model; fit is ongoing.
Kamano, Julia-Diaz, Lee, Matsuyama, Sato, arXiv: [nucl-th]
g(*) N  h N : in progress
g N  K L : in progress
Electromagnetic part