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# Overview of the EBAC@JLAB progress - PowerPoint PPT Presentation

Overview of the EBAC@JLAB progress. B. Juli á -D í az Departament d’Estructura i Constituents de la Mat è ria 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).

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### Overview of the EBAC@JLAB progress

B. Juliá-Díaz

Departament d’Estructura 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)

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:

J=1/2

J=3/2

J=3/2

J=1/2

0p

D33 (1700)

S31 (1620)

L=1, S=1/2, J=3/2-

S11 (1535)

D13 (1520)

L=1, S=1/2, J=1/2-

L=1, S=1/2, J=1/2-

L=1, S=1/2, J=3/2-

0s

P11 (939)

P33 Δ(1232)

L=0, S=1/2, J=1/2+

L=0, S=3/2, J=3/2+

qqq

Δ : 1600, 1620, 1700, 1750, 1900, …

The Δ (1232) and others

100

Δ (1232)

πN  X, πN

• The Delta (1232) resonance stands as a clear peak

• The region 1.4 GeV – 2 GeV hosts ~ 20 resonances

(LIJ)

PDG *s and N*’s origin

π

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 >

• N*s

EBAC@JLAB

Reaction Data

N* properties

N-N* form factors

Lattice QCD

QCD

e.g: p η

• Key points:

• Couplings of mesons to baryons

• Electromagnetic vertices

• Coupling of resonances to MB

• Electromagnetic structure of resonances

e.m.

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

σTOT (b)

MS

• Non-resonant + resonant

• Dressed resonant vertex

• Resonance self energies

• Non-resonant amplitude (resummation)

CC

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)

Δ: 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

i.e. VNN,N

Full approach described in great detail:

A. Matsuyama, T. Sato, T.-S.H. Lee, Phys. Rep. 2007

CC

Full approach described in great detail:

A. Matsuyama, T. Sato, T.-S.H. Lee, Phys. Rep. 2007

CC

Dynamical CC|SL/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

(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

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

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

Tech

EBAC

SAID06

N

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

Meson-baryon (iii)

• Amplitudes compared to GWU/SAID amplitudes for the I=1/2 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

  

H. Kamano, B. Julia-Diaz, TSH Lee, A. Matsuyama, T. Sato, Phys. Rev. C 79 (2009) 025206



   (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

 

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, p’s 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

Suzuki, BJD, HK, AM,TSHL, TS, in preparation (2009)

• Strong pieces fixed

• E.g.e.m. vertex of nucleon: fixed

• Electromagnetic structure of resonances

Q2 independent analyses?

Error?

Which N*s ? All?

p+n

• Comparison to data

• Total cross section

• Differential cross sections

• Target polarization

p0p

σTOT (b)

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

• 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)

• 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 W=1.65 and Q2=4 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)

*N  N up to W=1.6 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

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

END

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 <= 2-GeV nucleon resonance region.

B. Julia-Diaz, T.-S.H. Lee, A. Matsuyama, T. Sato, Phys. Rev. C 76, 065201 (2007)