Transcript N – N* Form Factors from the MAID Analysis L. Tiator Johannes Gutenberg-Universität Mainz in collaboration with D.

N – N* Form Factors
from the MAID Analysis
L. Tiator
Johannes Gutenberg-Universität Mainz
in collaboration with
D. Drechsel (Mainz) and S. Kamalov (Dubna)
 Introduction: Inelastic electron scattering
 The unitary isobar model MAID and our analysis techniques
 Transition Form Factors
a) N – D form factors at low and high Q2
b) N – Roper form factors and comparison with JLab analysis
c) detailed results for: D13(1520), S11(1535), F15(1680)
d) some results for: S11(1650), D15(1675), P13(1720)
 Comparison with the naive non-relativistic quark model
 Summary and Conclusions
Inclusive Cross Section for Real and Virtual Photo Absorption
Inelastic Electron Scattering in the Resonance Region
in general:
transition form factors can only be obtained by
•
partial wave analysis
•
and background / resonance separation
Definition of the N-N* Form Factors
reduced
multipoles:
in our MAID analysis the resonances are dressed
dressing and undressing can be studied in Dynamical Models:
e.g. Kamalov, Yang, Drechsel, L.T.
and Sato, Lee, Julia-Diaz
in most cases quark models calculate the bare resonance couplings
a direct comparison with exp. analysis is not possible,
e.g. Giannini on the hypercentral quark model
partial wave analysis
with resonance and background separation
for helicity amplitudes and transition form factors
we need the imaginary parts of the resonance multipoles
data base for pion electroproduction
data in the D region up to W = 1.3 GeV
JLab/Hall C
Frolov
1999
pp0
Q² = 2.5 - 4.3 GeV²
Bates
Mertz et al.
2001
pp0
Q² = 0.127 GeV²
Mainz
Pospischil et al.
2001
pp0
Q² = 0.127 GeV²
Bonn
Bantes, Gothe
2002
pp0
Q² = 0.6 GeV²
Mainz
Elsner et al. / Stave et al.
2006
pp0
Q² = 0.05-0.2 GeV²
JLab/Hall A
Kelly et al.
2007
np0
Q² = 1.0 GeV²
JLab/CLAS
Villano et al.
2008 prelim.
pp0
Q² = 6.0 – 7.9 GeV²
data up to the 3rd resonance region up to W = 1.7 GeV
JLab/CLAS
Joo et al.
2002 / 2003
pp0
Q² = 0.4 – 1.8 GeV²
JLab/CLAS
Joo et al.
2004
np+
Q² = 0.4 - 0.65 GeV²
JLab/Hall A
Laveissiere et al.
2004
np0
Q² = 1.0 GeV²
JLab/CLAS
Egiyan et al.
2006
np+
Q² = 0.3 – 0.6 GeV²
JLab/CLAS
Ungaro et al.
2006
pp0
Q² = 3.0 – 6.0 GeV²
JLab/CLAS
Park et al.
2008
np+
Q² = 1.7 – 4.5 GeV²
data base for pion electroproduction
older data from SAID data base up W = 2 GeV
DESY, DNPL, BONN …
1971 - 1999
pp0
Q² = 0.1 – 4.3 GeV²
DESY, DNPL, BONN …
1973 - 1999
np+
Q² = 0.1 – 4.4 GeV²
DNPL, …
1971 - 1988
pp-
Q² = 0.5 – 1.4 GeV²
E/M and S/M ratios for the ND transition
analysis
analysis
the analyses are based on p0 data from JLab, Mainz, Bonn and Bates
new Mainz08 analysis also uses preliminary JLab data from Villano et al
1) REM remains small and negative
2) RSM becomes much flatter around ~ 10%
fit A
fit B
Ji, Ma, Yuan, PRL 90, 2003
pQCD with angular momentum effects
Nucleon -> Delta on the Lattice
dynamical fermions – mp down to 360 MeV
C. Alexandrou et al., 2008
GM : main problems at small Q²
REM, RSM : in agreement
within large uncertainties
transition form factors of the Roper
comparison of MAID and JLab analysis
A1/2
MAID07 analysis
with p0 data of
Joo et al, 2002
Ungaro et al, 2006
S1/2
transition form factors of the Roper
comparison of MAID and JLab analysis
A1/2
JLab analysis
with p+ data of
Joo et al, 2004
Park et al, 2007
S1/2
transition form factors of the Roper
comparison of MAID and JLab analysis
A1/2
results from:
Maid07
JLab
and
new Maid analysis
with Park data
S1/2
Nucleon-Roper Transition Form Factors on the Lattice
~ S1/2
~ A1/2
Huey-Wen Lin, ECT* Trento 2008
details and update tomorrow on this workshop!
Transverse Charge Densities of the Nucleon and N -> Roper
(in collaboration with Marc Vanderhaeghen)
Updated Form Factors for higher Resonances
comparison with:
• Maid2003 (EPJ A17, 2003, 357)
• Maid2007 (EPJ A34, 2007, 69)
• very recent (2008)
with K. Park p+ data included in our database
some changes for the D13, no change for the F15
no changes for the S11 resonances
here the new p+ data make some considerable difference
Comparison with the naive non-relativistic quark model
Summary and Conclusions
•
the GM form factor of the D(1232) can be extracted
directly from the inelastic cross section with high accuracy
• all other electric, magnetic and charge form factors can only be
extracted from partial wave analysis
• mostly due to JLab data on p(e,e´p0)p we could extract reliable ffs of
P33(1232)
P11(1440)
D13(1520)
S11(1535)
F15(1680)

GM
GE
GC

GM
GE
GC
GE
GC

GM
----- GC
----- GE

GM
GC
•
recent JLab data on p(e,e´p+)n help to remove correlations
between partial waves, e.g. between P33 and P11
large effects also for D15 and P13
•
longitudinal form factors can be best analyzed
with the L-T interference cross section dsLT/dW
as in the Hall A experiment at Q²= 1 and backward angles
if possible more of such kind of exp. should be done in the future
•
the database for the neutron is very limited
our analysis is based on 890 data points from 1971-1988
and most of our neutron ffs are not very conclusive
new data are needed on d(e,e´p -p)n
Form Factors in the Electroproduction Process
Form Factors in MAID2007