overview of the ebac@jlab progress

Overview of the EBAC@JLAB progress

B. Juliá-DíazDepartament d’Estructura i Constituents de la MatèriaUniversitat 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)

B. Julia-Diaz, Overview of the EBAC@JLAB progress, PWA, Bad Honnef 2009


Baryon Resonances

ΔNExciting 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:

P11 (939)

0s

0p

L=0, S=1/2, J=1/2+P33 Δ(1232)L=0, S=3/2, J=3/2+

S11 (1535)L=1, S=1/2, J=1/2-

D13 (1520)L=1, S=1/2, J=3/2-

S31 (1620)L=1, S=1/2, J=1/2-

D33 (1700)L=1, S=1/2, J=3/2-

J=1/2 J=3/2 J=3/2 J=1/2

qqq


The Δ (1232) and others

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

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

πN

X

, πN

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

Δ : 1600, 1620, 1700, 1750, 1900, …

Δ (1232)Δ (1232)

100


PDG *s and N*’s origin

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 >

π N(LIJ)

N*s


Our plan and method


EBAC@JLAB

N* propertiesN-N* form factors

QQCCDD

Lattice QCDHadron Models

Dynamical Coupled-Channels Analysis @ EBAC

Reaction Data


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)

How do we produce meson-baryon states?

• Directly• Through MB states• Through MMB states

• We need to incorporate

all the possibilitiesUnitarity: Coupled-channels

σTOT (b)

p

MS


C.C. ingredients

Non-resonant + resonant

Dressed resonant vertex

Resonance self energies

Non-resonant amplitude (resummation)

CC


MBMB

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)

CC

Full approach described in great detail:

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


i.e. VNN,N

CC




Resonance t

CC




Dynamical CC|SL/EBAC

∫vgt

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


Hadronic part(essential starting point)


Meson-baryon building

N

(1) SAID Energy dependent PWA with fake error bars

(2) SAID Energy independent PWA

(3) EXP DATA

Bg N* param FIT

Fine tune

MINUIT used extensively

REFIT (almost final)


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

Tech

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


Meson-baryon

N

EBACSAID06


Meson-baryon (ii)

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

d/d Polarization


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

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

Real part of the amplitude

N


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


(II)

(Using the MB model of BJD, AM, TSHL and TS, Phys. Rev. C 76, 065201 (2007))

Data handled with the help of D. Arndt

Invariant massdistributions

Phase space

Full model

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


Properties of N*


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 states

Extraction of Resonances from Meson-Nucleon Reactions.N. Suzuki, T. Sato, T.-S.H. Lee, Phys. Rev. C 79 (2009) 025205

Resonance Mass


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

Current N*


Electromagneticpart


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

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

σT

OT (b

)

p0p Comparison to data Total cross section Differential cross

sections Target polarization

p+n


Single pion electroproduction

Delta region: We revisited the

original SL model and extracted the form factors of NDelta transition from single Q2 fits.

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


Single pion electroproduction

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

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


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

END

N* properties

N* properties from the EBAC N modelN. 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


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 reactionsH. 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)

overview of the ebac@jlab progress

Documents

bad honnef

jlab progressb

n n n nare

s originmost

mesonbaryon dynamics

mesonbaryon states

lee argonne

matsuyama shizuokat