Analysis of 2p Production
presented by V.I.Mokeev
gp→2pN exclusive channels in N* studies.
•modeling of 2p photo- and electroproduction by tree
level meson-baryon diagrams.
•phenomenological analysis within the framework of
JLAB-MSU model.
•N* studies in combined analysis of major exclusive
channels. Argonne-Osaka coupled channel approach.
•Conclusions.
V.I.Mokeev N* Analysis Workshop’
1
The p-p+p electroproduction amplitudes are needed for credible
evaluation of N* parameters in coupled channel analysis.
Exclusive channels in pN
scattering responsible for
ISI&FSI in meson electroproduction
CLAS data on meson electroproduction
at Q2<4.0 GeV2
p(e,e’)X
(trigger)
p(e,e’p)p0
p(e,e’p+)n
p(e,e’pp+)pp(e,e’pp+)X
V.I.Mokeev N* Analysis Workshop’
2
Why the studies of 2p electroproduction are important.
D33(1700) electrocouplings
from world data on 1p
electroproduction
from CLAS data on
2p electroproduction
combined analysis of
1p/2p CLAS data
V.I.Mokeev N* Analysis Workshop’
3
Meson-baryon (MB) models
(partial list of references).
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
L. Luke, P. Soding, Springer Tracts in Modern Physics 59 (1971) 39.
L.Y. Murphy, J.-M. Laget, DAPNIA-SPHN-96-10.
J.A. Gomez Tejedor, E. Oset, Nucl. Phys. A571 (1994) 667.
J.A. Gomez Tejedor, E. Oset, Nucl. Phys. A600 (1996) 413.
J.C. Nacher, et. al., Nucl. Phys. A695 (2001) 295.
S. Ong, J. Van de Wiele, Phys. Rev. C63 (2001) 024614.
W. Roberts, A.Rakotovao, hep-ph/9708236
W. Roberts, T.Oed, Phys. Rev. C71 (2005) 055201.
M. Hirata, K. Ochi, T. Takaki, Phys. Rev. C56 (1997) 1472.
M. Hirata, N. Katagiri, T. Takaki, Phys. Rev. C67 (2003) 034601.
M. Ripani, V.I. Mokeev, et. al., Nucl. Phys. A672 (2000) 220.
V.I. Mokeev, et. al., Phys. of Atom. Nucl. 64 (2001) 1292.
V. Bernard, N .Kaiser, U.G. Meissner, Eur. Phys. J. A11 (2001) 209.
A. Fix, H. Arenhovel, Eur. Phys. J. A25 (2005) 115.
V.I.Mokeev N* Analysis Workshop’
4
Valencia group approach.
(applicable at W<1.6 GeV)
M=p,r; B=p,D,P11(1440),D13(1520),
D33(1700); relevant for W<1.6 GeV
Isobar channels: pD, rp, pP11(1440)
& pN background
non fully relativistic description
(resolved in ref. 6 at p.5);
c-numbers instead of vertex functions
(in part resolved in ref. 6 at p.5) ;
no ISI&FSI effects
The contributions:
-pD Born terms
- to pD extra terms of JM06
- to direct 2p production of JM06
-s-channel N* excitation
V.I.Mokeev N* Analysis Workshop’
5
Fully relativistic description. W.Roberts approach.
p,V-mesons and all N*,D* of 1/2, 3/2 spin are included. A general framework for
most comprehensive MB description in N* excitation region.
N
r
g
N*,D*
p
Open problems:
•reliability of effective MB lagrangians→test
against data on N* LS partial decay widths;
•vertex functions, most of them are still unknown;
•ISI&FSI should be implemented
V.I.Mokeev N* Analysis Workshop’
6
A.Fix and H.Arenhövel approach.
M=p,r,s, B=N,D
All N*,D* with masses less then 1.8
GeV are included to s-channel
amplitudes.
Effective description of ISI&FSI
within the framework of
diffractive absorptive ansatz
Open problems:
•completeness of mechanisms at
high W;
•credibility of approximations for
ISI&FSI, considering huge
absorptive effects
V.I.Mokeev N* Analysis Workshop’
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How well MB approaches working?
Reasonable description of fully integrated cross-sections in all approaches, BUT
huge ad hoc absorptive corrections at W>1.6 GeV.
0p0p
ABBHHM, TAPS data in
gp→p
comparison with A.Fix,
H.Arenhovel model
V.I.Mokeev N* Analysis Workshop’
8
Cont’d
gp→p+p0n
TAPS
data
gp→p0p0p
E.Oset,
et.al.
model
E.Oset,et.al.
model
Discrepancies
Due to problems with description of 1-diff cross-sections neither of MB
approaches was ever used to extract N* parameters from the 2p photo and
electroproduction data. V.I.Mokeev N* Analysis Workshop’
9
New prospects for N* studies in 2p production. Effective lagrangians +
phenomenological parametrization hybrid approach.
ELSA, MAMI, GRAAL photo- and
CLAS
electroproduction
data
extended amount of measured
observables considerably.
CLAS electroproduction data.
For unpolarized beam/target, the
final state, gr,v→p-p+p reaction
offers 9 independent 1-differential
cross-sections in each (W&Q2)
bin. All these cross-sections are
available from CLAS for the first
time.
Contributing mechanisms may be
established in phenomenological
analysis of all available data
combined. It is joint JLAB/MSU
effort.
V.I.Mokeev N* Analysis Workshop’
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JLAB-MSU model (JM05) for 2-p electroproduction.
V.I. Mokeev, V.D.Burkert et.al., Proc. of the Workshop NSTAR2005, World
scientific, p.47
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 and 3/2+(1720) candidate.
•Reggetiezed Born terms & effective FSI&ISI
treatment (Ref. 11 p.5).
•extra pD contact term
•All well established N* with rp decays
+P11(1710)&P13(1720) 3-star states and
3/2+(1720) candidate.
•Diffractive ansatz for non-resonant
part & r-line shrinkage in N* region.
V.I.Mokeev N* Analysis Workshop’
11
con’d
Quasi-2-body mechanisms included
3-body processes
(p-)
•for p+D013(1520) set of Born terms similar
to what was used for pD isobar channels.
(P++33(1640)) (p+)
F015(1685)
•for p+F015(1685), p-P++33(1640) 3-body contact
term with exponential propagators of isobars
in 2 body intermediate states.
Direct 2p production.
Exchange processes,
parameterized as:
M
d
g

 A (W , Q )  U p / g  U
2
V.I.Mokeev N* Analysis Workshop’
1
p
W
2
4
e
2
b ( P - P min )
( P1 P2 )
12
Evidences for processes beyond isobar channel
superposition in 2p production.
CLAS data M.Ripani, V.D.Burkert, et. al.
Q2=0.95 GeV2
2p direct mechanisms
The contributions from all isobar channels combined still
underestimate 2p cross-sections. 2p direct mechanisms are needed
to reproduce CLAS/world data.
V.I.Mokeev N* Analysis Workshop’
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Evidences for exchange mechanisms in direct 2p
production from the CLAS data.
E93-006 CLAS data fit with
remaining mechanisms:
W=1.49 GeV
Q2=0.65 GeV2
exchange processes
Q2=0.95 GeV2
3-body phase space
remaining mechanisms
shown on slide 6
V.I.Mokeev N* Analysis Workshop’
14
p+p-p cross-sections off protons from the fit of mass and
p- angular distributions within the framework of JM05.
s, mcbn
CLAS data M.Ripani, V.D.Burkert, et. al.
Q2=0.65 Gev2
Q2=0.95 Gev2
Q2=1.30 Gev2
Reasonable description of invariant mass and p- angular
distributions were achieved without any need for an additional
mechanisms beyond implemented to JM05.
V.I.Mokeev N* Analysis Workshop’
W, GeV
15
Global fit of complete set of unpolarized 1-differential cross-sections within the
framework of JM06 model (1.3<W<1.6 GeV & 0.25<Q2<0.60 GeV2) .
JM06 full
p-D++
p +D 0
2p direct
ai-angular distributions were
calculated with parameters of
JM06 fitted to 6 other 1-diff.
cross-sections.
Successful description of all E94-005
data was achieved.
Complete data on unpolarized
1-differential cross-sections for the
first time available from CLAS
allowed us to establish all
significant mechanisms contributing
to the 2p electroproduction.
V.I.Mokeev N* Analysis Workshop’
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Modification of parameterization for direct 2p amplitudes
JM05
JM06
JM06
+

A (W )  U p  g U p e
bt
pp
-
( Pp + Pp )
t p p -  ( Pp - - Pp )
2

A (W )  U p  g U p e
bt
pp
-
bt
( Pp + Pp ) e
t gp +  ( Pp + - Pg )
2
V.I.Mokeev N* Analysis Workshop’
gp
+
t gp +

A (W )  U p  g U p e
bt
pp
-
( Pp + Pp  ) e
t g p   ( P p  - Pg )
bt g p 
t gp 
2
17
P11(1440) and D13(1520) electrocouplings.
P11(1440)
D13(1520)
from analysis of E94-005 CLAS 2p
data within the framework of JM06
from analysis of 1p CLAS data
from analysis of E93-006 CLAS 2p
data within the framework of JM05
combined analysis of 1p/2p
CLAS data
V.I.Mokeev N* Analysis Workshop’
18
Combined analysis of major exclusive electroproduction channels
within the framework of the coupled channel (cc) approach, using
phenomenological input from JM06
Argonne-Osaka
approach
(TS.H.Lee, et.al.) is only available
worldwide, capable to account for
full complexity of FSI in the ppN final
states.
resulting AO amplitudes
“bare” amplitudes, established
within the framework of JM06
“bare’ amplitudes from other
electroproduction channels
ppN unitarity cut
V.I.Mokeev N* Analysis Workshop’
19
Current efforts in combined 1p/2p analysis.
Hall B group & EBAC collaboration.
•
The amplitudes of all significant mechanisms in the 1p/2p exclusive channels
were determined in phenomenological analysis of the CLAS data
(I. Aznauryan for 1p, JM06 for 2p). Modification of these amplitudes by FSI,
is under evaluation, using AO approach at 0.25< Q2<1.5 GeV2 and W<1.5
GeV, where only 1p/2p channels contribute
•
1p/2p CLAS electroproduction data will be re-fitted, using non-resonant
amplitudes accounting for FSI. Clobal fit of observables from major
exclusive channels, accounting for unitarity, will be gradually extended up to
2.0 GeV W, allowing us to extract most reliable data on electrocouplings for
an entire excited nucleon spectrum.
•
Studies of underlying MB/partonic
mechanisms for remaining JM06
phenomenological terms will be carried out.
Expected outcome:
a)
b)
MB vertex off-shell behavior → input for lattice simulation(?);
Understanding of the transition from MB mechanisms to pD rp GPD’s,/other
partonic processes needed for N* studies at high Q2.
V.I.Mokeev N* Analysis Workshop’
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What mechanisms behind JM06 phenomenological terms?
JM06
phenomenological
terms will be replaced
by MB amplitudes,
derived from modern
effective Lagrangians
of
the
outlined
approach
+
residual
phenomenological
contributions, if any.
S.Capstick, T.-S.H.Lee, A. Kiswandhi model
For particular mechanisms isolated in JM06 the sum is rather limited
V.I.Mokeev N* Analysis Workshop’
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Conclusions.
•
Considerable extension of the data on 2p photo- and electro- production from
recent experiments, carried out worldwide on continues beams with 4p
detectors, open up new opportunities for N* studies. Global analysis of full set of
unpolarized observables for the first time available from CLAS, allowed us to
develop the JM06 model with most complete accounting for all significant
mechanisms. These studies demonstrated capability to map-out all sizeable
mechanisms from the fit of various observables combined. The amplitudes,
determined for all contributing mechanisms, provide necessary input for
extraction of N* parameters in the cc analyses.
•
Global analysis of observables from major photo- / electro- production channels
combined, implementing unitarity within the framework of most advanced
Argonne-Osaka approach, offers promising way for credible N*/non-resonant
processes separation. Therefore, all necessary tools are available to extract
reliable values of N* electrocouplings, at various photo virtualities Q2 and to
improve knowledge of N* hadronic parameters.
•
2p exclusive channels offer very reach information both on resonant and nonresonant processes, vital for modern hadronic physics. Wealthy of this
information may be accessed only in combined efforts, including
phenomenological mapping of contributing mechanisms, comprehensive FSI
treatment and the studies of actual mechanisms behind phenomenology within
the framework of meson-baryon and partonic degrees of freedom.
V.I.Mokeev N* Analysis Workshop’
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BACK-UP
V.I.Mokeev N* Analysis Workshop’
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Modeling of 2p production by tree level
meson-baryon diagrams.
•
Set of tree level meson-baryon diagrams.
Particular meson and baryon states were
implemented based on:
a) manifestation of unstable particles in invariant
mass distributions;
b) established in analysis 1p production and
experiments with pion beams;
c) needs to improve description of particular data
features.
• Full sets of diagrams were created, applying all
possible permutations for meson/baryon legs
V.I.Mokeev N* Analysis Workshop’
24
Fit of E94-005 CLAS 2p data (L.Elouadrhiri, G.Fedotov, et. al.) collected
at low W&Q2 within the framework of JM05 model.
full
p-D++
p+D 0
2p direct
JM05 succeeded to describe p+p, p-p+
p-p mass and p- angular distributions,
Failure in description of p+ and
pf angular distributions, revealed
necessity to modify direct 2p
production mechanisms.
V.I.Mokeev N* Analysis Workshop’
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General problems of MB approaches.
• Available MB models are unable to establish all significant mechanisms
contributing to the 2p production due to lack of guidance from
fundamental theory and insufficient amount of analyzed observables to
determine complexity of contribution processes from the data fit.
• Most of MB vertex function are unknown and may be only fitted to the
data.
• FSI were either neglected or treated in oversimplified approximations.
Comprehensive approach for description of FSI complexity in the 3 body
ppN final state was needed. Such approach has been developed just
recently by Argonne-Osaka collaboration (see T-S.H.Lee talk, hepth/0608051).
Neither of MB approaches was ever used to extract N* parameters
from the 2p photo and electroproduction data.
V.I.Mokeev N* Analysis Workshop’
26
An additional contact terms in pD channels needed to fit
data.
M

g
t


g



 ( A (W )   U D g U p Pp + B (W )   U D  g U p ( 2 Pp - Pg ))
1
t-
2
2
 = 1.64 GeV
t  ( Pg - Pp )
2
2
V.I.Mokeev N* Analysis Workshop’
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The amplitudes for gpp+F015(1685) and
gpp-P++33(1600) channels.

2
g

M  A (W , Q )     U p g U p ( PF 15  Pp + )  exp



1
2
g

M  A (W , Q )     U p g U p
 exp
2
t
m

p*

2



(
M
M
)
F
15


p p

2



F 15

 
2

1
 ( M p - p - M P 33 ) 



2
 P 33
Pp  Pp 



V.I.Mokeev N* Analysis Workshop’




28
Fit of single differential cross-sections from E93-006
experiment within the framework of JM05.
Full calculations
gpp-D++
gpp+D0
gpp+D13(1520)
gprp
gpp-P33++(1640)
gpp+F150(1685)
direct 2p production
V.I.Mokeev N* Analysis Workshop’
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Selected p-p+p cross-sections calculated within the framework of
JM05, most closed to the E93-006 CLAS data.
p+ p, p- p+, p -p invar. masses and p- angular
distributions were fitted within the framework
of JM05 (V.Mokeev et.al. , Proc. of NSTAR2005
Workshop, p.47)
Q2=0 65GeV2
experimetal data from M.Ripani et. al. ,
Phys. Rev. Lett.91, 022002 (2003)
W-interv., GeV
2 thresh.
1.41-1.54
2.45
1.56-1.64
2.19
1.66-1.76
2.04
1.79-1.89
2.06
Q2=0 95GeV2
V.I.Mokeev N* Analysis Workshop’
Q2=1 30 GeV2
30
Evidence for complementary contributions to
pD isobar channels.
W=1.76 GeV Q2=0.95 GeV2
extra contact term in pD
channels
on
off
gp→p+D0:
ds/dM, mcbn/GeV
JM05 full:
p+D0
extra contact term in pD
channels
on
off
W=1.81 GeV Q2=0.95 GeV2
p+p mass, GeV
V.I.Mokeev N* Analysis Workshop’
p-p mass, GeV
32
Manifestation of gp→p-P33++(1640) and
gp→p+F15(1685) isobar channels.
W=1.89 GeV
Q2=0.95 GeV2
JM05 full
p-P33++(1640) and
p+F15 (1685) isobar
channels off
gp→p+F15(1685)
gp→p-P 33(1640)
Contribution from
isobar channels:
p-P33++(1640)
p+F15 (1685)
V.I.Mokeev N* Analysis Workshop’
33
Resonant/non-resonant mechanism separation.
full JM06 calculations
non-resonant part
resonant part
Combined fit of all unpolarized
1-diff. cross-sections allows us
to isolate resonant/non-resonant
parts, exploiting difference in shapes
of their cross-sections.
V.I.Mokeev N* Analysis Workshop’
34
Total p-p+p cross-sections calculated within the
framework of JM06, most closed to the preliminary
CLAS data at 0.25<Q2<0.60 GeV2 and W<1.57 GeV.
preliminary CLAS data,
exper. E94-005,
L.Elouadrhiri, G.Fedotov, et.al.
Q2-interv.,
GeV2
2 thresh.
0.250-0.400
2.80
0.400-0.500
1.80
0.500-0.600
1.70
V.I.Mokeev N* Analysis Workshop’
35
High lying N* electrocouplings.
D33(1700), P13(1720)
resonances mostly
decay with 2p
emission. 1p data do
not have enough
sensitivity to these
states.
First preliminary data on
Q2 -evolution of
S31(1620), D13(1700),
D33(1700), P13(1720)
electromagnetic form
factors were obtained
from analysis of CLAS
E93-006 experiment on
2p electroproduction.
D33(1700)
P13(1720)
V.I.Mokeev N* Analysis Workshop’
D33(1700)
P13(1720)
36