Overview of the ebac@jlab progress
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Overview of the [email protected] 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

Overview of the [email protected] 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)


Overview of the ebac jlab progress

The problem


Baryon resonances

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:

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


The 1232 and others

N*: 1440, 1520, 1535, 1650, 1675, 1680, ...

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


Pdg s and n s origin

(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


    Our plan and method

    Our plan and method


    Ebac@jlab

    Dynamical Coupled-Channels Analysis @ EBAC

    [email protected]

    Reaction Data

    N* properties

    N-N* form factors

    Hadron Models

    Lattice QCD

    QCD


    E m probes

    E.m. probes

    e.g: p η

    • Key points:

      • Couplings of mesons to baryons

      • Electromagnetic vertices

      • Coupling of resonances to MB

      • Electromagnetic structure of resonances

    e.m.


    Multi step unitarity

    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

    σTOT (b)

    MS


    C c ingredients

    C.C. ingredients

    • Non-resonant + resonant

    • Dressed resonant vertex

    • Resonance self energies

    • Non-resonant amplitude (resummation)

    CC


    Mb mb

    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

    i.e. VNN,N

    Full approach described in great detail:

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

    CC


    Resonance t

    Resonance t

    Full approach described in great detail:

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

    CC


    Dynamical cc sl ebac

    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


    Hadronic part essential starting point

    Hadronic part(essential starting point)


    Meson baryon building

    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


    Technical aspects

    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


    Meson baryon

    Meson-baryon

    EBAC

    SAID06

    N


    Meson baryon ii

    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


    Meson baryon iii

    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


    Overview of the ebac jlab progress

      

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

    


    Overview of the ebac jlab progress

       (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

     


    Properties of n

    Properties of N*


    Resonance states

    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, 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


    Current n

    Current N*

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


    Electromagneticpart

    Electromagneticpart


    Single pion production

    Single pion production

    • Strong pieces fixed

    • E.g.e.m. vertex of nucleon: fixed

    • Electromagnetic structure of resonances

    Q2 independent analyses?

    Error?

    Which N*s ? All?


    Single pion photoproduction

    Single pion photoproduction

    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)


    Single pion electroproduction

    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)


    Single pion electroproduction1

    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 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)


    In progress 2009

    Single and double meson production

    *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


    Overview of the ebac jlab progress

    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 <= 2-GeV nucleon resonance region.

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


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