Reaction models of meson production reactions

Reaction models of meson production reactions

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

Universitat de Barcelona (Spain)

B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008

ΔN

The spectrumExciting the substructure we 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)

100


The current PDG values πN

(LIJ)

N*s

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 >

Are they all? 4* ? 3* ? 2* ? Properties are extracted from

meson production reactions:N N N N


Electromagnetic probes

Electrons are well suited for baryon resonance studies, several facilities have used them over the last years:• Jefferson LAB (USA)• GRAAL (Grenoble)• MAMI (Mainz)• BATES (MIT)• ELSA (Bonn)• SPring 8 (Japan)

Courtesy of D. Leinweber 1. Hard enough: structure needs to

be excited.

2. Not too hard: we may find out the constituents but not the way they are glued together.

3. Range of Q2: electrons allow to vary the momentum transferred, thus mapping out the structure.

e.m.


desirable properties for

reaction models


Basic properties1. Unitarity contraint built in

Basic


Basic properties: unitarity

How do we produce meson-baryon states?• Directly• Through MB states• Through MMB states

• We need to incorporate

all the possibilities

σTOT (b)p

S†S=1

Unitarity: Coupled-channels



2. Simultaneous treatment of • Electromagnetic

• Strong interactions

Basic


Basic properties | Consistency

• Couplings of mesons to baryons

• Electromagnetic vertices

• Coupling of resonances to MB• Electromagnetic structure of

resonances

Consistent description of strong and e.m.

e.m.





3. Simultaneous description of:• Hadroproduction observables ( N, N, , N, …)

• Electroproduction observables ( N, N, , , N, …)

Basic


Basic properties | some data

p0p p+n

p+

Basic

NMN





3. Simultaneous description of:• Hadroproduction observables ( N, N, , N, …)

• Electroproduction observables (* N, N, , , N, …)

4. Chiral symmetry constraints built in

5. Connection with quark gluon mechanisms at high energies

Basic


Basic properties | constraints

Quark/gluon

N* Physics

ChP

T

Basic


current reaction

models (used also with e.m.)


dynamical coupled

channels


Dynamical Coupled-Channels

Non-resonant + resonant

Dressed resonant vertex

Resonance self energies

Non-resonant amplitude

Full integration ?

Effective lagrangians, quark models, …?

How many channels ?

E.m and hadronic simultaneously?


Dynamical CC | Juelich

∫vgt

Reactions studied:

No e.m. yet

Juelich

Hadronic part: (Effective Lagrangians)

(fit SAID) (~ 1.9 GeV)

η

2006S. Krewald, J. Haidenbauer, O. Krehl, A. Gasparian, C. Hanhart, Haberzettl

Juelich N, ηN, , ,

8 PWA (J<5/2) | 4 explicit N*

(expected progress from

Nakayama, Haberzettl, et al.)


Dynamical CC|Juelich (II)

∫vgt

Physics:

Unitarity fulfilled

Most relevant channels included (hadronic)

Chiral constraints

Off-shell effects included U-channel resonances

Strong coupling responsible for dynamical generation of the P11(1440) resonance

Technical Slow evaluation (probably) Parallel version(?) Manpower (?)


Dynamical CC | SL/EBAC

∫vgt

Reactions studied:

(fit DATA)(W<1.65 GeV)

* (W=1232 MeV)

η (W< 2 GeV)

(W< 2 GeV)

(W< 2 GeV)

(W< 2 GeV)

Sato-Lee/EBAC

Hadronic part: (effective lagrangians)

(fit SAID+DATA),

, N, ,

J. Durand, B. Julia-Diaz, H. Kamano, T.-S. H. Lee, A. Matsuyama, M. Paris, B. Saghai, T. Sato, N. Suzuki, K.Tsushima

2008, η, , , , , ,



Dynamical CC | SL/EBAC

∫vgt

Physics:

Consistent study of most production reactions

Most relevant channels included

Unitarity fulfilled

Off-shell effects included

Exact treatment of 3 body cut

Chiral constraints

Dynamical model solved for complex E

K-matrix version also available U-channel resonances

Technical

Parallel computing version used extensively Slow evaluation for final state observables

Talks by Sato, Kamano, Paris


Dynamical CC|Taipei/Mainz

∫vgt

Reactions studied:

No e.m. yet

(expected progress soon)

Taipei/Mainz

Hadronic part:

N N (fit SAID)

N ηN

Off-shell effects included

Accurate description of hadronic part Many resonances (33 with 4 new) Only two channels Phenomenological width Unitarity Speed plot used to extract N* parameters

Chen, Kamalov, Yang, Drechsel, Tiator 2007, η



coupled channels k-

matrix


Coupled-channels K-matrix

i[]

Key assumption:

Examples :

Talk by Strakowsky

o SAID

o Giessen

o KVI


CC K-matrix |SAID

i[]

Reactions studied:

*

, η(‘)

SAID (R. A. Arndt, W. J. Briscoe, R. L. Workman, I. Strakovsky)

A and B are purely phenomenological polynomials

N, N, ηN

Hadronic part:

η,

2007

Reference to many other groups


CC K-matrix |SAID

i[]

Physics:

N* properties from complex E plane

Single energy and energy dependent fits

Q2 evolution of multipole amplitudes

Unitarity below threshold

(unphysical) extrapolation (to get pole positions) K-matrix approximation

Technical

Fast evaluation

Accurate 2

Great one and two meson database handling

Updated regularly Open-access (ssh, web) (http://gwdac.phys.gwu.edu)


CC K-matrix |Giessen

i[]

E.m. Reactions studied:

(fit SAID), ()

, , η,

Giessen (Feuster, Penner, Mosel)

Hadronic part:

(fit SAID, KH84)

, η, ()

N, N, N, , , ηN, N

V = vbg +vR

2005

S,P,D, F PWs | 11 N*s


Physics:

Unitarity fulfilled within the model

Hadron and e.m. consistently studied (using effective lagrangians)

U-channel resonances included K-matrix approximation

Speed plot to extract N* properties (for “technical reasons”)

Technical

Fast evaluation

CC K-matrix |Giessen (II)

i[]


CC K-matrix |KVI

i[]

E.m. Reactions studied:

(fit SAID), ()

,, η,

KVI Scholten, Usov, Timmermans, Shyam, ..

Hadronic part:(effective lagrangians)

(fit SAID) (~1.7 GeV)

, η, ()

N, N N, , , ηN, N

2008

S,P,D PWA | 11 explicit N*


unitary isobar model


Unitary Isobar Model

i[]

Reaction model assumption:

Reactions studied:

N N

*N N

MAID

N η(‘)N (eta(‘)-MAID)

N N (2pi-MAID)

*N (kaon-MAID),

Examples (up and running): MAID, JLAB/Yerevan

Talks by Tiator and Aznauryan

N, N

2007

Up to F waves, 13 explicit N*D. Drechsel, S.S. Kamalov, L. Tiator, Fix


UIM|MAID

i[]

The phase of the multipole (non-res + res) taken as:

Ensures Watson theorem is fulfilled Assumption above 2 threshold

Resonant part:

Non resonant part:

t from SAIDFull t matrix:


Extract resonance structure (pion electroproduction)

Single energy and energy dependent fits

Unitary below threshold Mixture of PV and PS coupling Hadronic information taken from GWU/SAID Several relevant channels not included, e.g. , ,… Principal value not included

Technical

Fast evaluation, Accurate 2

Open-access (http://www.kph.uni-mainz.de/MAID)

Being updated regularly

No error estimation of N* properties

i[]

UIM|MAID(2)


UIM | CB-Elsa

i[]

Reaction model assumption:

Reactions studied:

N N

N ηN

CB-ELSA (Thoma, Anisovic, …)

N

N N N

N, N, , 2008

S,P,D, F | 21 explicit N*, 5 new


tree diagram


Tree-diagramMain motivation:

Studies of reaction mechanims

Key assumption:

Reactions assumed to be dominated by a small number of resonances (e.g. specific kinematical regions)

T V = vbg +vR


Tree-diagram (II)

Reactions studied: N (Adelseck, Bennhold, Mart, Saghai,…) *N N (Oh, Lee, Titov, Zhao) N N (too many to be listed)

N N (Oset, Nacher, Roca, Arenhoevel,…)

*N N (Mokeev et al.)

o And many more of course

Essentially:o Non-resonant usually

obtained from Efective Lagrangians, e.g.:

o The resonant part :Effective LagrangiansQuark modelsParametrizations

Talk by Fernández-Ramírez


Physics:

Good for exploratory calculations

Chiral constraints (in some of them)

Not Unitary Principal value not included No off-shell effects

Technical

Fast evaluation

Tree-diagram (III)


Tree-diagram | Example JLAB-MSU V.Mokeev, V.Burkert, (CLAS)

Motivation:

Extract N* properties from recent CLAS * data

Extract Q2 evolution of N* photocouplings

JM full-++

+0

2 direct

Procedure:

Select direct and isobar production processes

2007

P33(1640)F15(1685)D13(1520)

pp

CLAS

CLAS (06)


Final wish list Unified easy access/database (ALL DATA for single and double

meson) GWU@SAID JLAB ?

At least two coexisting competitive full coupled-channels models needed to study model dependence

EBAC Juelich ? (Taipei/Mainz)

Cross computations between the different approaches E.g. SAID using EBAC non-resonant terms

Comparisons of non-observable quantities E.g. Juelich non-resonant vs EBAC non-resonant

Build the bridge to microscopic studies

END

Talks by Ramalho, Giannini, Roberts, Cloet, Richards, Lin, Gross, Zhao, Polyakov, …

Reaction models of meson production reactions

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