Overview of the EBACJLAB progress

1
Overview of the EBAC_at_JLAB progress

• B. Juliá-Díaz
• Departament dEstructura i Constituents de la
  Matèria
• Universitat de Barcelona (Spain)

• The players
• H. Kamano (JLab)
• T.S.H. Lee (Argonne, JLab)
• A. Matsuyama (Shizuoka)
• T. Sato, N. Suzuki (Osaka)
• B. Saghai, J. Durand (Saclay)

2
The problem
3
Baryon Resonances
Exciting the substructure we can learn about the
forces which keep the quarks together, e.g. using
the quark model picture some of the predicted
states are
J1/2
J3/2
J3/2
J1/2
0p
D33 (1700)
S31 (1620)
L1, S1/2, J?3/2-
S11 (1535)
D13 (1520)
L1, S1/2, J?1/2-
L1, S1/2, J?1/2-
L1, S1/2, J?3/2-
0s
P11 (939)
P33 ?(1232)
L0, S1/2, J?1/2
L0, S3/2, J?3/2
qqq
4
The ? (1232) and others
100
? (1232)
pN ? X, pN

• The Delta (1232) resonance stands as a clear
  peak
• The region 1.4 GeV 2 GeV hosts 20 resonances

?
5
PDG s and Ns origin
(LIJ)
p
N

• Most of their properties are extracted from
• ?N ? ? N
• ?N ? ? N
• Are they all genuine quark/gluon excitations?
• N qqq
• Is their origin dynamical?
• E.g. some could be understood as arising from
  meson-baryon dynamics
• N MB

Ns
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Our plan and method
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EBAC_at_JLAB
Reaction Data
N properties N-N form factors
Lattice QCD
Hadron Models
QCD
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E.m. probes

• e.g ?p ???
• Key points
• Couplings of mesons to baryons
• Electromagnetic vertices
• ?
• Coupling of resonances to MB
• Electromagnetic structure of resonances

e.m.
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Multi step (unitarity)

• How do we produce meson-baryon states?
• Directly
• Through MB states
• Through MMB states
• ?
• We need to incorporate all the possibilities
• Unitarity
• Coupled-channels

?p?
sTOT (?b)
MS
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C.C. ingredients

• Non-resonant resonant
• Dressed resonant vertex
• Resonance self energies
• Non-resonant amplitude (resummation)

CC
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MB?MB
We introduce explicitly (impose) a minimal
number of resonances, 16 of 23 (4 and 3
from PDG) N S11(2), P11(2), P13(1), D13(1),
D15(1), F15(1) ? S31(1), P31(1), P33(2), D33(1),
F35(1), F37(1)
Full approach described in great detail A.
Matsuyama, T. Sato, T.-S.H. Lee, Phys. Rep. 2007
CC
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i.e. V?N??N,?N
Full approach described in great detail A.
Matsuyama, T. Sato, T.-S.H. Lee, Phys. Rep. 2007
CC
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Resonance t
Full approach described in great detail A.
Matsuyama, T. Sato, T.-S.H. Lee, Phys. Rep. 2007
CC
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Dynamical CCSL/EBAC

• Physics
• Unitarity fulfilled within the model
• Most relevant channels included
• Consistent study of all production reactions
• Exact treatment of 3 body cut
• Technical
• Parallel computing version exists
• Slow evaluation

?vgt
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Hadronic part(essential starting point)
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Meson-baryon building
(1) SAID Energy dependent PWA with fake error
bars
FIT
Bg
N param
(2) SAID Energy independent PWA
REFIT (almost final)
MINUIT used extensively
(3) EXP DATA
Fine tune
?N
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Technical aspects

• Time gain resulting from using parallel
  computers scales linearly with the number of
  processors
• First parallelization in Energy
• Second parallelization in partial wave
• BSC, Spain (340 kh), PI B.
  Julia-Diaz
• NERSC LBNL (500 kh), PI TSH Lee

• Involved system of coupled integral equations
  with singularities. No further approximations
  taken.
• Need for extensive parameter search. Several
  unknowns e.g. couplings of resonances to MB
  states
• We developed a parallel code, CCEBA, and got
  several supercomputing resources

Tech
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Meson-baryon
EBAC
SAID06
?N
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Meson-baryon (ii)
d?/d?
Polarization
B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T.
Sato, Phys. Rev. C 76, 065201 (2007) data
obtained through D. Arndt et al, SAID ,
gwdac.phys.gwu.edu
?N
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Meson-baryon (iii)

• Amplitudes compared to GWU/SAID amplitudes for
  the I1/2 sector
• Total Cross sections compared to experimental
  data
• Prediction for the total cross sections for each
  individual channel

Real part of the amplitude
B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T.
Sato, Phys. Rev. C 76, 065201 (2007)
?N
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?? ? ???
H. Kamano, B. Julia-Diaz, TSH Lee, A. Matsuyama,
T. Sato, Phys. Rev. C 79 (2009) 025206
??
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?? ? ??? (II)
Invariant mass distributions
Full model
Phase space
H. Kamano, B. Julia-Diaz, TSH Lee, A. Matsuyama,
T. Sato, Phys. Rev. C 79 (2009) 025206
(Using the MB model of BJD, AM, TSHL and TS,
Phys. Rev. C 76, 065201 (2007)) Data handled with
the help of D. Arndt
? ?
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Properties of N
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Resonance states
Analytic continuation of T(W) to the unphysical
sheet by using contour deformation Pole can be
both in the non-resonant and resonant
amplitudes Pole of T as a function of W, ps
are arbitrary
Resonance Mass
Extraction of Resonances from Meson-Nucleon
Reactions. N. Suzuki, T. Sato, T.-S.H. Lee, Phys.
Rev. C 79 (2009) 025205
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Current N
Suzuki, BJD, HK, AM,TSHL, TS, in preparation
(2009)
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Electromagneticpart
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Single pion production

• Strong pieces fixed
• E.g. e.m. vertex of nucleon fixed
• ?
• Electromagnetic structure of resonances

Q2 independent analyses? Error? Which Ns ? All?
?
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Single pion photoproduction
?p??n
?p??0p

• Comparison to data
• Total cross section
• Differential cross sections
• Target polarization

sTOT (?b)
B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T.
Sato, L.C. Smith, Phys. Rev. C77, 045205 (2008)
?
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Single pion electroproduction

• Delta region
• We revisited the original SL model and extracted
  the form factors of N?Delta transition from
  single Q2 fits.

Julia-Diaz, Lee, Sato, Smith, Phys. Rev. C 75,
015205, (2007)
?
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Single pion electroproduction

• On going work
• Fix the strong pieces
• Resonance content fixed in strong part
• First fit the structure functions available where
  they have been extracted
• First goal is to go up to W1.65 and Q24 GeV2
• Current status
• Preliminar Q2 evolution of helicities available
• Need to control de error

B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T.
Sato, L.C. Smith, Phys. Rev. C77, 045205 (2008)
?
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In progress ( 2009)

• N properties
• N properties from the EBAC ?N model
• N. Suzuki, B. Julia-Diaz, H. Kamano, A.
  Matsuyama, T.-S.H. Lee, T. Sato.
• Extraction of N ?MB and N?? N decay vertices
• B. Julia-Diaz, H. Kamano, A. Matsuyama, T.-S.H.
  Lee, T. Sato, N. Suzuki

• Single and double meson production
• ?N ? ?N up to W1.6 GeV (preparation)
• H. Kamano, B. Julia-Diaz, A. Matsuyama, T.-S.H.
  Lee, T. Sato
• Currently using CLAS structure functions to fix
  the Q2 evolution of the helicity amplitudes
• PRELIMINARY RESULTS AVAILABLE
• ?N ? ??N (preparation)
• B. Julia-Diaz, H. Kamano, A. Matsuyama, T.-S.H.
  Lee, T. Sato

END
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EBAC progress
Extraction of Resonances from Meson-Nucleon
Reactions. N. Suzuki, T. Sato, T.-S.H. Lee, Phys.
Rev. C 79 (2009) 025205 Dynamical
coupled-channels study of pi n -- pi pi n
reactions H. Kamano, B. Julia-Diaz, T.-S.H. Lee,
A. Matsuyama, T. Sato, Phys. Rev. C 79 (2009)
025206 Coupled-channels study of the pion- p --
eta n process J. Durand, B. Julia-Diaz, T.-S.H.
Lee, B. Saghai, T. Sato, Phys. Rev. C 78, 025204
(2008) Dynamical coupled-channels effects in
pion photoproduction B. Julia-Diaz, T.-S.H. Lee,
A. Matsuyama, T. Sato, and L.C. Smith, Phys. Rev.
C 77, 045205 (2008) Dynamical coupled-channels
model of pi N scattering in the W nucleon resonance region. B. Julia-Diaz, T.-S.H.
Lee, A. Matsuyama, T. Sato, Phys. Rev. C 76,
065201 (2007)