reaction models of meson production reactions
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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
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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.
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
desirable properties for
reaction models
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
Basic properties1. Unitarity contraint built in
Basic
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
Basic properties1. Unitarity contraint built in
2. Simultaneous treatment of • Electromagnetic
• Strong interactions
Basic
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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.
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
Basic properties1. Unitarity contraint built in
2. Simultaneous treatment of • Electromagnetic
• Strong interactions
3. Simultaneous description of:• Hadroproduction observables ( N, N, , N, …)
• Electroproduction observables ( N, N, , , N, …)
Basic
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
Basic properties | some data
p0p p+n
p+
Basic
NMN
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
Basic properties1. Unitarity contraint built in
2. Simultaneous treatment of • Electromagnetic
• Strong interactions
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
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
Basic properties | constraints
Quark/gluon
N* Physics
ChP
T
Basic
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
current reaction
models (used also with e.m.)
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
dynamical coupled
channels
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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?
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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.)
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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 (?)
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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, , , , , ,
16 PWA (J<9/2) | 16 explicit N*
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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
16 PWA (J<9/2) | 33 explicit N*
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
coupled channels k-
matrix
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
Coupled-channels K-matrix
i[]
Key assumption:
Examples :
Talk by Strakowsky
o SAID
o Giessen
o KVI
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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)
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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[]
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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*
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
unitary isobar model
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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:
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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)
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
tree diagram
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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)
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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)
B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008
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, …
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