a partial wave analysis of pion photo- and electroproduction with maid
DESCRIPTION
A partial wave analysis of pion photo- and electroproduction with MAID. introduction a dynamical approach to meson electroproduction the unitary isobar model MAID comparison of multipoles between MAID and SAID resonance parameters and transition form factors summary and outlook. - PowerPoint PPT PresentationTRANSCRIPT
A partial wave analysisA partial wave analysis
of pion photo- and of pion photo- and electroproductionelectroproduction
with MAIDwith MAID introduction
a dynamical approach to meson electroproduction
the unitary isobar model MAID
comparison of multipoles between MAID and SAID
resonance parameters and transition form factors
summary and outlook
models and techniques of different groupsmodels and techniques of different groups
why partial wave analysiswhy partial wave analysis
• learn about nucleon resonancesin particular about their e.m. structuretransition moments, form factors GE, GM, GC
• study threshold amplitudesto compare with ChPT
• obtain cross sections and amplitudes over a wide range of energies for dispersive studies- sum rules: GDH, FFR, etc.- two-photon reactions: Compton, VCS, SSA, etc.
• find missing or exotic resonances
K-matrix K-matrix
approximationapproximation
MAIDMAID
the Mainz-Dubna Unitary Isobar the Mainz-Dubna Unitary Isobar ModelModel
the Resonances in MAIDthe Resonances in MAID are dressed resonances are dressed resonances
K-matrix unitarization
unitarization phasedetermined by the Watson theorem, below 2 threshold
relaxed above 2 threshold
currently about 20 000 photoproduction points in our data base
Results Results
onon
photo- and electroproduction photo- and electroproduction
of of
nucleon resonancesnucleon resonances
threshold threshold photoproduction photoproduction
simple background (non-unitarized)
imag. part
real part
threshold threshold photoproduction photoproduction
unitarized background (K-matrix approx.)
imag. part
real part
threshold threshold photoproduction photoproduction
phenomenological loop contribution added
imag. part
real part
loop contribution
Unitarity at Eta ThresholdUnitarity at Eta Threshold
Data: GDH collaboration, Mainz, 2006 (PRC 74)
Mainz 2006
Mainz 2006
(MAID uses SAID pion nucleon analysis)(MAID uses SAID pion nucleon analysis)
comparison between MAID and SAIDcomparison between MAID and SAID
comparison between MAID and SAIDcomparison between MAID and SAID
electroproduction analysis of nucleon resonances with MAID
currently about 140 000 electroproduction points in our data base
Delta PDelta P3333(1232) and D(1232) and D1313(1520) (1520) resonancesresonances
Roper PRoper P1111(1440) and S(1440) and S1111(1535) (1535) resonancesresonances
Roper S11(1535)
summary on MAID techniquessummary on MAID techniques
field theoretical background in tree approximation
pion loop contributions in K-matrix approximationguarantees a unitarized background
non-Born bg terms account for missing loop contributions a) empirical terms near threshold for E0+, S0+
b) PS-PV mixing at higher energies in E0+, S0+, M1-, S1-
nucleon resonance excitation in s-channel Breit-Wigner parametrization(MAID strategy: as few as necessary, in Maid07: 13 res.)
Q2 dependent transition form factorslead to superglobal energy- and Q2 dependent solutions
how can we improve the background in isobar models?
1) fixed-t disp. relations: changes only real parts of multipoles
2) parametrize -loop effects: can also change imaginary parts of multipoles but without predictive power
3) apply the new Dubna-Taipei-Mainz dynamical model DMT2007
most important candidates that need to be improved:
Real E0+ Im E0+
Real S0+ Im S0+
Real M1+
Real S1+
Real M2-
OutlookOutlook