Transcript Dynamical coupled-channels study of photo- and electro-production reactions

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
1. Excited Baryon Analysis Center (EBAC) @JLab
2. Recent results from EBAC-DCC analysis of
ep  e’pN reactions
3. Current work on “Complete Experiment” of
pseudoscalar meson photoproduction reactions
Excited Baryon Analysis Center @ Jefferson Lab
http://ebac-theory.jlab.org/
Founded in January 2006
Reaction Data
Objectives and goals:
Through the comprehensive analysis
of world data of pN, gN, N(e,e’) reactions,
Dynamical Coupled-Channels Analysis @ EBAC
 Determine N* spectrum
(masses, widths)
N* parameters
Hadron Models
Lattice QCD
QCD
 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 model @ EBAC
For details see Matsuyama, Sato, Lee, Phys. Rep. 439,193 (2007)
 Partial wave (LSJ) amplitude of a  b reaction:
coupled-channels effect
 Reaction channels:
 Potential:
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
Meson cloud
×
Other analysis
“Complete Experiment” of
pseudoscalar meson photoproduction reactions
Measure ALL polarization observables needed
“Complete Experiment” = to determine amplitudes (up to overall phase)
unpolarized diff. crs. sec.
8 /16 observables needed!
Chiang, Tabakin PRC55 2054 (1997)
single spin
 Measurement
of gN  KY
pol. obs. is very active.
How much critical
are the polarization
observables
beam-target
on constrainingreaction
models and
extracting
OVER-COMPLETE
experiment
planned
+
N* parameters ? by CLAS for g p  K Y, g n  KY.
beam-recoil
target-recoil
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.
 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.
 Examined significance of the polarization observables for
construction of reaction models and extraction of N* parameters.
 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
pNpN
: fitted to the SAID PWA up to W = 2 GeV.
Julia-Diaz, Lee, Matsuyama, Sato, PRC76 065201 (2007)
pNppN
: cross sections calculated with the pN model; fit is ongoing.
Kamano, Julia-Diaz, Lee, Matsuyama, Sato, PRC79 025206 (2009)
pNhN
: fitted to the data up to W = 2 GeV
Durand, Julia-Diaz, Lee, Saghai, Sato, PRC78 025204 (2008)
Electromagnetic part
 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ppN
: 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KL
: in progress