1. Checked inside kinematics area:
JLAB-MSU isobar model (JM) for
description of double charged pion
production off proton by real and
virtual photons in N* excitation region.
Checked inside kinematics area:
W<1.9 GeV, Q2<1.5 GeV2
Version 2005’
(JM05)

2. JLAB-MSU model for 2-p electroproduction (2003’-version).
3-body processes
Quasi-2-body mechanisms included
All well established N* with pD decays +P33(1600)&P11(1710)&P13(1720)&P33(1920) 3-star states
Minimal set of Reggetized gauge invariant Born terms
Effective treatment of couplings with other open channels
All well established N* with rp decays
+P11(1710)&P13(1720) 3-star states.
Diffractive ansatz for non-resonant rp
production

3. Evaluation of 3-body amplitudes
The decay amplitudes
as well as W-dependence for decay width of intermediate unstable particles
have been determined from phenomenological Lagrangians: ,

4. JLAB-MSU model (2003’-version).
Residual mechanisms, beyond shown on the plots, were parameterized
either as 3-body phase space C(W,Q2) or through a set of partial waves
with J<13/2. Both lead to a similar description.
Details of the 2003’-version of model may be found in:
M.Ripani et. al., Nucl. Phys., A672, 220 (2000);
V.Mokeev, et. al., Phys. of Atom. Nucl., 64, 1292 (2001);
V.D.Burkert, et.al., Phys. of Atom Nucl.,66, 2199 (2003);
V.D.Burkert, et. al., Phys. of Atom Nucl., 67, 1018 (2004);

5. Cross-sections and amplitudes
Kinematics variables for final state:
Sp+p-, Sp+p, Wp-, a.
All angles are
determined in CM-frame
Sij=Mij2, GeV2
is the angle between
2 planes:
1) composed by momenta
of photon and p-,2) compo-
sed by momenta of p’ & p+

6. Con’t Cross-sections and hadronic currents (unpolarized e- beam):
MN=0.938 GeV
3-b phase
space
inv. flux
For unpolarized proton target and the final state density matrixes are:
KL,e,eL are equivalent photon vector and virtual photon polarizations
dt=dsp+p-dsp+pdWp--da
W is invariant mass of the final
hadronic system

7. Current and helicity amplitudes
Photon polarization vectors
For electron scattering lab. frame:

8. Gi were taken from analyses of experiments with hadronic probes
Resonant part
The strong
decay amplitudes
Gi are N* hadronic decay widths to the final
states of certain helicity; MN* is resonance
mass; Pi is the final particle mometum averaged
over intermediate unstable particle line.
Gi were taken from analyses of experiments with hadronic probes

9. Electromagnetic transition amplitudes
transverse photons
longitudinal photons
are electromagnetic transition N* form factors
fitted to the data
Multiplicative factors for electromagnetic transition and hadronic
decay amplitudes we determined in a way to get Breit-Wigner
formula for resonant part of cross-section, expressed through hadronic
and electromagnetic N* decay widths (D.Luke, P.Soding, Springer Tract in
Modern Physics, 59 (1971)). All these factors were obtained for relations
between hel. amplitudes and cross-section on slides 6,7

10. Non-resonant mechanisms in pD isobar channels.
Minimal set of Reggetized
gauge invariant Born
terms Fp
Electromagnetic pion (Fp), proton (Fp) and hadronic (FpND) form factors were used for respective vertices
FpND
Special approach was
developed to account for
ISI&FSI M.Ripani, et.al.,
Nucl. Phys., A672, 220
(2000) Fp

11. Non-resonant amplitudes in pD channels.
Born terms were evaluated in the effective Lagrangian approach developed
in A. Bartl, W. Majerotto, D. Schildknecht, Nuovo Cimento 12A,
703 (1972) . See Born amplitudes in M.Ripani et. al., Nucl. Phys.,
A672, 220 (2000) p.p
New feature: the particle off-shell behaviour description
Vertex functions for Born diagrams on previous slide:
SLAC C. J. Bebek e. a.
Phys. Rev. D17 (1978) 1693
NN scattering R. Machleidt in
Advances in Nucl. Phys. V19 (1979)

12. Reggezeition and current conservation.
Current conservation for Born terms is insured by the relations
between vertex functions:
Reggeization procedure
M. Guidal J.-M. Laget, M. Vanderhaeghen Phys. Lett. B400 (1997) 6
Gauge invariance restoration after Reggezeition

13. H.Haberzettl, private communication Fi Fi
Word-Takahashi-Slavnov identity
H.Haberzettl, private
communication
Hadronic
vertex
Fi
Hadronic
vertex
Fi
WTS identity is fulfilled with determined above operators Fi for Born terms of our model, if hadronic vertex functions are related as written on slide 10.

14. THE INITIAL AND FINAL STATE INTERACTIONS.
Developed based on approach proposed by
K. Gotfried, J. D. Jackson, Nuovo Cimento 34, 736 (1964)
The basic physical assumption:
the reaction mechanisms factorization as sequence of ISI,
main process, FSI
the consideration at ISI & FSI effects absorption of ingoing and
outgoing particles
See details in
M. Ripani, V. Mokeev, e. a. Nucl. Phys. A672 (2000)

15. Electroproduction data fit. A possible new 3/2+(1720) baryon state.
CLAS data fit
Contributions from conventional
states only
Fit with new 3/2+(1720) state
M.Ripani et. al.
Phys. Rev. Lett.91, (2003)
Difference between curves due to signal from possible 3/2+(1720) state

16. Fitted differential 2p cross-sections.

17. Description of 1.7 GeV mass region.
Two alternative ways to describe CLAS data inside 1.7 GeV structure:
Modification of hadronic couplings for P13(1720) PDG state
with respect to established values
Implementation of new baryon state with Jp = 3/2+.
M, MeV
G,MeV
GpD/G, %
GrP/G,
modified
P13(1720)
1725±20
114±19
60±12
19±9
PDG
absent
70-85
“new state”
3/2+(1720)
1720±20
88±17
41±13
17±10

18. p+D13 0(1520) isobar channel 3-body processes
Quasi-2-body mechanisms included
Minimal set of Born terms similar to what was
used for pD states, except an additional g5 matrix
to account for the opposite parities of D and
D13(1520)

19. Description of p+p, p-p mass distributions at W=1.56 GeV.
gp→p+D13(1520):
absorbed in
3b ph.space
included
contribution from
sub-channel

20. Description of p+p, p-p mass distributions at W=1.79 GeV.
Implementation of
gp→p+D13(1520)
sub-channel allowed
to reproduce CLAS
data

21. Diagrams for gp→p+D13(1520) channel

22. p+D13(1520) isobar channel in p- angular distributions.
Implementation of
p+D13(1520) isobar
channel keeps description
of p- angular distributions
reasonably well.

23. The contribution from p+D13 0(1520) isobar channel to the total p+p-p cross-sections.
Full JM03
calculations
3/2+(1720) candidate
state off
p+D13(1520) isobar
channel

24. Comparison between various ways to describe structure around 1.7 GeV W.
Full JM03
calculations
3/2+(1720) off
p+D13(1520)
channel
3/2+(1720) off, while
p+D13(1520) channel
is enhanced to reproduce
p-p+p total cross-section
around 1.7 GeV W

25. Comparison between various ways to describe structure around 1.7 GeV W.
Attempt to substitute
the signal from 3/2+(1720)
candidate state, enhancing
the contribution from
p+D13(1520) isobar
channel is failed
Signal from 3/2+(1720)
state exists.

26. Non-resonant mechanisms for rp isobar channel
Non-resonant mechanisms for rp isobar channel. Modified diffractive ansatz.
conv. diffr. ansatz
Modifications:
insure proper amplitude behavior near threshold
accounts for r-line shrinkage at near/sub threshold
areas in transition between photon and r meson
W in GeV; A0=12, D=0.25 GeV,
l0= 0.77 GeV, Dl=0.3 GeV

27. Description of the CLAS data on p+p- inv
Description of the CLAS data on p+p- inv. mass distributions with W-independent values of magnitude Adiff for non-resonant diffractive rp production.
Q2=1.30 GeV2
W=1.79 GeV
Adiff=3.0
ds/dM mb/GeV
Adiff=12.0
Mp+p- GeV
W=2.04 GeV
There is no way to
describe the data in entire
W-area, covered by
measurements, with Adiff
independent from W
ds/dM mb/GeV
Mp+p- GeV

28. Description of the CLAS data within the framework of modified diffractive ansatz.
N.Shvedunov, et. al., accepted by Phys. of
Atom. Nucl.,
p+p- mass
distributions
at various W
and Q2=1.30 GeV2
ds/dMp+p mb/GeV
Mp+p- GeV

29. Cont’d Reasonable description of p+ p- mass distributions and their
dependence from W and Q2 was within the framework
of developed modification for description of non-resonant rp
production.

30. 2p direct production mechanisms at the photon point.
JLAB-MSU model version, described on p.2-29
W=1.45 GeV
JLAB-MSU model 05’, see p
2p direct production
Preliminary real photon
data from:
M.Bellis, et. al.,
(CLAS Collaboration) Proc of
NSTAR2004 Workshop,
March 24-27,2004, Grenoble,
France, World Scientific 2005,
ed. by J.-P.Bocquet, V.Kuznetsov,
D.Rebreyend, 139

31. Manifestation of 2-p direct production at Q2>0.
W=1.49 GeV
JLAB-MSU model 05
Q2=0.65 GeV2
Q2=0.95 GeV2
2003’-version
2p direct production

32. 2p direct production mechanisms and an additional tensor term in pD channels needed to fit data.
2 = 1.64 GeV2

33. p+D0 with complementary tensor term
2p direct production and complementary tensor term at the photon point.
W=1.63 GeV
W=1.78 GeV
p+D0 with complementary tensor term

34. Manifestation of complementary tensor term in pD channels at Q2>0.
W=1.84 GeV Q2=0.65 GeV2
JLAB-MSU model:
improved
initial
Channels:
p-D++ rp
p+D0
p+D13(1520)
2p direct
W=1.84 GeV Q2=0.95 GeV2
Structure around D0 peak in
p-p and high mass part in p+p
mass distributions are better
described, implementing an
additional tensor structure
for pD chanels

35. Evidence for gpp+F015(1685) and gpp-P++33(1600) channels.

36. The amplitudes for gpp+F015(1685) and gpp-P++33(1600) channels.

37. Fit of 2p photoproduction data at high W after implementation of new isobar channels.
Full calculations
gpp-D++
gpp+D0
gprp
gpp-P++33(1600)
gpp+F015(1685)
2p direct

38. Total p+p- photoproduction cross-section off protons.
3/2+(1720) photocouplings adjusted to the real photon data. Hadronic couplings and mass derived from the fit of virtual photon data.
no 3/2+
full calculation
Background
Signal from 3/2+(1720) state
present, but masked by large
background
Resonances

39. Isobar channels at Q2=0. GeV2.
JLAB preliminary
SAPHIR
Calculations in JM05 2p
direct
full
p-D++
p+D0 rp
p-P++33(1600)
Points with bars correspond to
SAPHIR data on isobar channels
p+F015(1685)

40. Uncertainties in isobar channel separation at Q2=0 GeV2.
Parameters of 2p direct
production mechanisms as well
as magnitude of complementary
contact terms in pD channels
were varied within 30% s.
P33(1600), 3/2+(1720) candidate,
P13(1720), F35(1905), F37(1950)
photocouplings were varied
within 30% s
We selected calculated cross-
sections for which c2/ d.p.<
predetermined value, so they
are insight uncertainties for all
analyzed observables.

41. Description of single-differential cross-sections at Q2=0. GeV2.

42. Description of single-differential cross-sections at Q2=0. GeV2.
Various mechanisms have
particular manifestations,
which are different for
various kind of differential
cross-sections. However,
reflections of particular
mechanisms on observables
are highly correlated by
mechanism dynamics.

43. Description of single-differential cross-sections at Q2=0. GeV2.
Combined fit of all
observables enable us
to access dynamics of
contributing mechanisms.

44. Description of single-differential cross-sections at Q2=0. GeV2.

45. Total p+p- electroproduction cross-section off protons.
Initial values of N* photocouplings were taken from analysis of CLAS 2p data within the framework of 2003’-version of the JLAB-MSU model: V.Burkert et.al., Nucl. Phys. A737, S231 (2004) and further adjusted to the data, using recent version of model.
s mb
Q2=0.65 GeV2
Q2=0.95 GeV2
Signal from possible 3/2+(1720)
state ~ 1.7 GeV becomes more
pronounced at Q2>0.5 GeV2 due to
considerable growth of N*/Bckgr.
ratio in electroproduction.
Q2=1.30 GeV2
W, GeV

46. Description of single-differential cross-sections at Q2=0.65 GeV2.
calculated in JM03’
All other lines are the
same as on slides

47. Description of single-differential cross-sections at Q2=0.65 GeV2.

48. Description of single-differential cross-sections at Q2=0.65 GeV2.
p+ D13(1520)
isobar channel

49. Description of single-differential cross-sections at Q2=0.65 GeV2.

50. Isobar channels at Q2=0.95 GeV2

51. Description of single-differential cross-sections at Q2=0.95 GeV2.

52. Description of single-differential cross-sections at Q2=0.95 GeV2.

53. Description of single-differential cross-sections at Q2=0.95 GeV2.

54. Description of single-differential cross-sections at Q2=0.95 GeV2.

55. Isobar channels at Q2=1.30 GeV2.

56. Description of single-differential cross-sections at Q2=1.30 GeV2.

57. Description of single-differential cross-sections at Q2=1.30 GeV2.

58. Description of single-differential cross-sections at Q2=1.30 GeV2.

59. Description of single-differential cross-sections at Q2=1.30 GeV2.

60. Improvements in the fit of the 2p CLAS electroproduction data after implementation of new non-resonant mechanisms
Q2, GeV2
0.65
0.95
1.30
c2/d.p. 2003’-
version
3.91
3.30
2.26
c2/d.p. improved JLAB-MSU model
2.83
1.90
2.01
c2 was estimated from
comparison between
calculated and measured
1-diff. cross-sections
for entire set of data in
particular Q2-bin
Quality of CLAS data allows to describe all relevant mechanisms of 2p
production at W<1.9 GeV and Q2<1.5 GeV2 by meson baryon diagrams,
fitting theirs parameter to the data without any need for residual mechanisms
of unknown dynamics.
Essentials of JLAB-MSU model improvements are highlighted in:
V.Mokeev et. al., Proc of NSTAR2004 Workshop, World Scientific 2005 ed.
by J.-P.Bocquet, V.Kuznetsov, D.Rebreyend, 317

61. Further evidence for possible 3/2+(1720) state
Fit with 3/2+(1720)
3/2+(1720) off; variation of
electromagnetic, pD rP
hadronic couplings and masses
of P13(1720), P33(1600) states
P13(1720) BF(rP), extracted from
the fit within improved JLAB-MSU
model (no new state):
Q2, GeV
BF,%
63±25
20±10
discrepancy!
Preliminary real and published virtual photon data combined could be fitted
only if both possible new 3/2+(1720) and P13(1720) states contribute

62. cont’d Definitive conclusion
on origin of the structure at 1.7 GeV may be made after
2p real photon
data will be finalized

63. How unambiguously resonant part may be isolated in JM05 model?
Two ways of cross-section calculations were compared:
JM05 calculation with mostly phenomenological description for complementary contact terms in pD channels and parameterization of direct 2p mechanisms. Lorentz structure , kind of exchange mechanisms and unstable intermediate particle formation were accounted, while peculiar dynamic features were incorporated into vertex functions fitted to the data.
Implementation of particular mechanisms behind vertex functions, using as guide gauge invariance and crossing symmetry.
Signature for unambiguous N* part isolation within the framework of JM05 is successful data description in both mentioned above approaches with the same N* electrocouplings.

64. Complementary Born terms needed to provide gauge invariance in 2-body  channels after implementation of additional contact terms
Contact term ~A(W)
Contact term ~B(W)
Hadronic vertices
WTS is fulfilled with determined above complementary Born terms, if vertex function related as presented on slide 11.

65. JM05&description with extra Born terms on slide 63.
Full calculations
After
implementation
of additional
Born terms
JM05
Background
After
implementation
of additional
Born terms
JM05

66. JM05&description with extra Born terms on slide 63.

67. JM05&description with extra Born terms on slide 63.

68. JM05&description with extra Born terms on slide 63.
N*/background
separation is the same
in both ways of describing
non-resonant mechanisms
in pD channels.

69. 3-body mechanisms needed for guage invariance and crossing symmetry in r,vp  -++  -+p channel

70. continued
After substitution   q in written above terms, we found current conservation under the following relation
where ,  are parameters fitted to the data, F(Q2), FN(Q2), g(Q2,t) are presented on slides 10, 11 while FN(U), is determined as
For m = 1.23 GeV implemented term contribution to thetotal 2 cross-section <0.5 %
m m* running and fitted to the data
0.8 < m* < 0.9 GeV

71. JM05 & additional 3 body terms on slides 69, 70 for channel gp→p-D++→p-p+p.
Full calculations:
3-body terms
substitute part
of 2p direct mech.
JM05
Background:
3-body terms
substitute part
of 2p direct mech.
JM05 N*

72. JM05 & additional 3 body terms on slides 69, 70 for channel gp→p-D++→p-p+p.

73. JM05 & additional 3 body terms on slides 69, 70 for channel gp→p-D++→p-p+p.
The data are described
reasonably well in both
approaches with the same
values of N* electrocouplings
regardless differences in
N*/background separation.

74. JM05 & additional 3 body terms on slides 69, 70 for channel gp→p-D++→p-p+p.
Unambiguous isolation
of N* part is achieved
in JM05.

75. N*/background separation at Q2=0.65 GeV2.
N*/Total

76. Combined analysis of the CLAS data on 1p and 2p electroproduction
Data at Q2=0.65 GeV2 were analyzed. It is only photon
virtuality for which both 1p and 2p CLAS data exist so far.
Single pion data: ds/dW differential cross-sections:
p+ at W between GeV,
p0 at W between GeV;
beam asymmetries:
p+ and p0 at W between GeV
9870 data points
CLAS 1p data
K.Joo, L.C.Smith, et.al
Double pion data: p+p-, p+p, p-p mass and
CM p- angular distributions at
W between GeV
680 data points
The data are available in CLAS Physics DB:
CLAS 2p data
M.Ripani, V.D.Burkert,
et.al.
CLAS 1-p data (K.Joo, L.C.Smith, et.al.)
1p analysis models: I.G. Aznauryan, Phys. Rev. C68, (2003);
I.G. Aznauryan, et. al., Phys. Rev. C71,
(2005).

77. 1p CLAS/world data fit (step 1).
All available data on single pion electroproduction were fitted within the framework of 1p dynamical model (see ref. on p.76).
N* photocouplings were fitted to the CLAS data, using MINUIT minimization procedure. They were fixed at the values corresponded to single global minimum for 2/d.p.
Photocoupling uncertainties were derived from error matrix, evaluated at minimal 2/d.p. They may be larger due to possibilities of comparable data description within uncertainties, corresponded to various 2/d.p. outside the global minimum.

78. 2p CLAS data fit (step 2).
N* photocouplings were fluctuated around values extracted in 1p data fit within 30% s
For each set of photocouplings all measured single differential 2p cross-sections were estimated within the framework of JM05 model and c2/d.p.’s were obtained from comparison with CLAS 2p data
The sets of the N* photocouplings were selected, for which evaluated cross-sections are inside data uncertainties, applying restriction c2/d.p<3.0
Mean values in samples of selected photocouplings were assigned to A1/2 , A3/2 and S1/2 electromagnetic transition form factors. Respective dispersions were treated as form factor uncertainties

79. -The states with considerable 1p decays
N* photocouplings (in 10-3 GeV-1/2) extracted in analyses of 1p/2p exclusive channels at Q2=0.65 GeV2 N*
1p-2p analysis
(errors from procedure on p80)
1p analysis
(lower boundary for errors)
2p analysis
(errors from procedure on p.80)
A1/2
A3/2
S1/2
P11(1440)
21±4
33± 6
4± 4
(23±4)
40± 4
21± 9
35± 6
D13(1520)
-65± 4
62± 5
-35± 3
-67± 3
62± 4
-38± 3
-63± 12
62± 11
-40± 7
S31(1620)
16± 4
-28± 3
31± 3
13± 3
-25± 4
S11(1650)
43± 7
-6± 3
43± 2
-15± 2
44± 16
-8± 2
F15(1680)
-32± 5
51± 4
-15± 3
-38± 4
56± 2
-18± 2
-31± 8
52± 10
-14± 3
D33(1700)
44± 4
36± 4
-7± 4
58± 5
29± 3
-15± 5
49± 8
36± 8
-11± 4
D13(1700)
-21± 2
10± 1
-6± 8
-55± 7
0±8
-19± 3
11± 2
P13(1720)
55± 3
-68 ±4
45± 6
-48± 7
0±7
56± 6
-62± 9
(…) result from dispersion relations. Roper is only state with
A1/2 dependent from model for 1p analysis
-The states with considerable 1p decays

80. Search for N* photocouplings compatible both with 1p and 2p CLAS data.
N* photocouplings were varied inside uncertainties of 1p and 2p data fit for the states with major 1p and 2p decays respectively. Additional variation of pN BF within established uncertainties were applied. Common sets of N* electromagnetic/hadronic couplings were used to calculate 1p/2p differential cross-sections and LT’ structure functions for p+n and p0p exclusive channels. I.G.Aznayuryn dynamical model JANR were applied for analysis of 1p channels. JM05 model was used for analysis of p-p+p channel. Calculated observables were compared with recent CLAS 1p/2p data.
Sub-sets of N* photocouplings were selected, for which calculated observables both in 1p/2p channels were inside data uncertainties. For selected sub-sets of calculated observables c2 per data point span between (1p channels) and (2p channel)
Selected sub-sets of N* photocouplings, which provided good reproduction of both 1p and 2p data, were averaged for each state and mean values were treated as extracted from combined 1p/2p analysis, while their dispersions were considered as errors. The results are given in the Table (see p. 79)

81. 1p data description with N
1p data description with N* photocouplings from combined analysis of 1p/2p channels.
W=1.52 GeV
gvp→p0p
W=1.68 GeV

82. Cont’d gvp→p0p sLT’ All observables in 1p channel,
measured with CLAS, as well as
world data at Q2=0.65 GeV2 were
described pretty good in JANR
model, using sets of N*
photocouplings, derived in
combined 1p-2p analysis

83. 2p data description with N
2p data description with N* photocouplings from combined analysis of 1p/2p channels.
W=1.54 GeV Q2=0.65 GeV2
W=1.66 GeV Q2=0.65 GeV2
Bunches of curves correspond to calculated cross-sections with common sets of N* photocouplings

84. Integrated 2p cross-section
Con’t
Integrated 2p cross-section
Q2=0.65 GeV2
Calculations with common sets of N*
photocouplings provided good
description of all available 2p
cross-sections at Q2=0.65 GeV2
The results are presented in:
I.G.Aznauryan et. al., submitted to
Phys. Rev. C72, (2005)

85. *)1.65 GeV mass from our analysis
N* photocouplings and hadronic parameters from analysis of the CLAS 2p data within the framework of recent JLAB-MSU (JM05) model.
Fitted data: p+p-, p+p, p-p mass and CM p- angular distributions at 20 W-bins between GeV and photon virtualities Q2: 0., 0.65, 0.95, 1.30 GeV2. The data may be found in CLAS Physics DB:
Combined fit of 4 Q2 bins was carried out within a framework of 2005’ JLAB-MSU model. W-intervals between GeV, GeV, GeV, GeV were fitted independently.
Photocouplings and poorly known masses, pD and rp couplings of N* were varied and fitted to the data together with parameters of non-resonant mechanisms implemented to the 2005’ JLAB-MSU model. Hadronic couplings were further constrained, exploiting their Q2-independence. The photocouplings at 4 mentioned above Q2’s were derived from data fit for the states: P11(1440), D13(1520), S31(1620), S11(1650), P33(1600)*), F15(1685), D13(1700), D33(1700), P13(1720), candidate 3/2+(1720), F35(1905), P33(1920), F37(1950).
*)1.65 GeV mass from our analysis
Yes

86. Description of total p+p-p cross-sections with N
Description of total p+p-p cross-sections with N* electrocouplings hadronic and non-resonant mechanism parameters fitted to the data.
Parameter variations
N* photocouplings: within 30% s around values obtained in previous fit (2003’ JLAB-MSU model)
pD, rp decays: wide range, which led to the total width variation between MeV
N* masses: inside PDG uncertainties
Q2=0 GeV2
Q2=0 65GeV2
W-interv., GeV
2/d.p thresh.
2.45
2.19
2.04
2.06
Yes
Q2=0 95GeV2
Q2=1 30 GeV2
Sub-sets of calculated cross-sections most close to the data were isolated, applying restriction 2<2 thresh, listed in the table

87. Description of single-differential cross-sections with selected sets of variable parameters.
W=1.71 GeV and Q2=0.95 GeV2
Bunches of curves correspond
to calculated cross-sections,
applying restriction c2<2.05
Similar sets of observables
were fit in all available W and
Q2bins shown on previous slide
No/Yes

88. Q2-evolution of the photocouplings for N. ’s in mass range between 1
Q2-evolution of the photocouplings for N*’s in mass range between GeV, determined from analysis of CLAS 2p data.
P11(1440)
CLAS 2p data
analysis
PDG at Q2=0 GeV2;
1p-2p combined
CLAS data analysis
at Q2=0.65 GeV2
(A1/22+S1/22)1/2 *1000GeV-1/2
Yes
Q2 GeV2

89. Cont’d D13(1520) CLAS 2p data analysis (A1/22+S1/22)1/2, GeV-1/2
A3/2, GeV-1/2
PDG at Q2=0 GeV2;
1p/2p combined
CLAS data analysis
at Q2=0.65 GeV2
World data
before CLAS,
obtained in
analysis of 1p
electroproduction:
V.D. Burkert, et. al.,
Phys. Rev. C67,
(2003)
Q2 GeV2
Q2 GeV2

90. Cont’d S31(1620) S11(1650) (A1/22+S1/22)1/2 *1000GeV-1/2
Q2 GeV2
Q2 GeV2

91. Cont’d
F15(1685)
F15(1685)
D13(1700)
D13(1700)
Yes

92. Cont’d S31(1620), D13(1700), D33(1700), P13(1720) resonances mostly
decay with 2p
emission. 1p world
data before CLAS
at Q2>0 (black points)
have no enough
sensitivity to these
states.
D33(1700)
D33(1700)
First data on
Q2 -evolution of
S31(1620), D13(1700),
D33(1700), P13(1720)
photocouplings were
obtained from analysis
of CLAS experiments on
2p photo- and electro-
production.
P13(1720)
P13(1720)
No?Yes

93. Possible new baryon state 3/2+(1720).
recent CLAS 2p data
analysis
previous analysis
of CLAS data on
2p electro- production
Yes
Signal from possible new
baryon state was confirmed
in analysis of electro-
production data and observed
in real photon data.

94. N*’s heavier than 1.9 GeV. F35(1905) First data on Q2 -evolution of
P33(1920), F35(1905),
F37(1950)
photocouplings were
obtained from analysis
of CLAS experiments on
2p photo- and electro-
production.

95. N*’s heavier than 1.9 GeV.
P33(1920)

96. N*’s heavier than 1.9 GeV.
F37(1950)

97. Conclusions.
Phenomenological approach was developed for description of 2p production by real and virtual photons in N* excitation region and for the photon virtualities Q2<1.5 GeV2 with most complete treatment of all significant mechanisms. Manifestations of particular mechanism in various observables are different, but highly correlated by mechanism dynamics. Successful description of all unpolarized observables combined allowed to establish dynamics of contributing mechanisms from data fit.
We found no need for complementary mechanisms of unknown dynamics beyond incorporated in JM05. So, all significant mechanisms in 2p production were taken into account.
Successful description of most detailed data base on 2p photo and electroproduction unpolarized observables strongly support completeness and credibility of JM05 with respect to any other approach available. Currently JM05 is only available approach worldwide for studies of high lying N* (M>1,6 GeV) in 2p exclusive channel.
Alternative descriptions of non-resonant mechanisms: a) within the framework of JM05, incorporating phenomenological parametrization for part of mechanisms and b) implementation of explicit meson-baryon diagrams accounted for parametrized processes both result in reasonable fit of observables with the same values for N* electrocouplings. Therefore, we obtained evidence for unambiguous N* part separation achieved in JM05.

98. Cont’d
Successful description of all observables measured with CLAS for major
exclusive channels in N* excitation region: p+n, p0p, p+p-p, at Q2=0.65 GeV2 with
common values of N* electrocouplings provided strong support from experiment
part for reliability of non-resonant mechanism description and N*/background
separation in JM05.
The photocouplings in Q2-area between 0 and 1.5 GeV2 were extracted
from CLAS 2p photo- and electroproduction data for most N*’s with masses less
then 2.0 GeV. Q2-evolution of photocouplings for S31(1620), D13(1700),
D33(1700), P13(1720), F35(1905), P33(1920), F37(1950) states were
determined for the first time. Considerable improvement was achieved in our
knowledge on N* 2p decays as well as on most hadronic parameters for high
lying states.

99. Outlook
Reliable data on N* electrocouplings may obtained from combined fit of all observables in major exclusive channels in N* excitation region. TRUE Coupled Channel Approach is vital to establish framework for multi- channel analysis; to determine and isolate fake resonance behavior in observables; to pin down N* in particular for non-dominant exclusive channels.
First comprehensive data on Q2-evolution of photocouplings for many N*’s open up an opportunity to establish driving symmetry for quark binding potential in baryons and to access N* structure in terms of contributing 3q-configurations.
First comprehensive data on N* photocoupling evolution with Q2 offer most reliable estimation of the resonant parts in inclusive structure functions. The data on resonance contribution in inclusive processes are important in the studies of quark distributions and hadronization at high x-Bjorken as well as for understanding of quark-hadron duality.