Dynamical coupledchannels study of photo and electroproduction reactions

1
Dynamical coupled-channels study ofphoto- 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
2
Outline

• Excited Baryon Analysis Center (EBAC) _at_JLab
• Recent results from EBAC-DCC analysis of
• ep ? epN reactions
• Current work on Complete Experiment of
• pseudoscalar meson photoproduction
  reactions

3
Excited Baryon Analysis Center _at_ 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,
• 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 _at_ EBAC
N parameters
Lattice QCD
Hadron Models
QCD
4
Dynamical coupled-channels model _at_ 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 gt 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 lt 1.6 GeV Q2 lt 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 PRC55
2054 (1997)

• 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 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

10
Summary

• Presented our recent analysis of ep ? epN
  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 lt 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 lt
1.5 (GeV/c)2
13
Dynamical coupled-channels model _at_ 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, 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,
  arXiv0909.1129 nucl-th
• g() N ? h N in progress
• g N ? K L in progress

Electromagnetic part