Meson spectroscopy with unitary coupled-channels model

Satoshi Nakamura

Excited Baryon Analysis Center (EBAC), JLab

Collaborators : H. Kamano (RCNP), T.-S.H. Lee (ANL), T. Sato (Osaka U)

Why hadron spectroscopy ?

JPC , spectrum, decay pattern

key information

Quark-gluon dynamics (QCD) in non-perturbative regime

How

Partial wave analysis (PWA)

Data

Reliable analysis tool needed !

Analysis of three-meson productions

e.g., E852 (BNL) p p ppp p Chung et al., PRD 65, 072001 (2001)

isobar model * pp subsystem forms a resonance * 3rd p is a spectator

Question

Unitarity ?

Coupled-channels ?

3-body unitarity requires … Z-diagrams

Question to be addressed

How 3-body unitarity makes a difference in extracting hadron

properties from data ?

Method 1. Construct a unitary and an isobar models

2. Fit them to the same Dalitz plot

3. Extract and compare M* properties from them

(pole position, coupling strength to decay channels)

pp model

Coupled-channels eq. for pp scattering (L , I )

Fitted to data

Coupling strength to decay channels

Unitary model

Isobar model

a1(1230) f0 p0 r p

Coupling strength to decay channels

W=1 GeV p2(1670) r p f2 p0

Unitary

Isobar

[degree]

W=1.66 GeV