Proposal on the reaction model development for description
of exclusive electroproduction at high photon virtualities
V.I.Mokeev
JLAB
V.I.Mokeev, Meeting January 26 2015, Hall-B at JLAB
CLAS12
New Results on N* Electrocouplings from the CLAS
• N(1675)5/2-, N(1680)5/2+, N(1710)1/2+ electrocouplings were obtained from the p+n CLAS data at
1.5 <Q2<4.0GeV2 arxiv1412.0274 [nucl-ex];
• D(1232)3/2+, N(1440)1/2+, N(1520)3/2-, N(1535)1/2-, electrocouplings were determined at Q2<4.5 GeV2;
• Preliminary results on electrocouplings of D(1620)1/2-, , N(1650)1/2-, N(1680)5/2+, D(1700)3/2-,
N(1720)3/2+ are available at Q2 from 0.5 to 1.5 GeV2
N(1520)3/2-
N(1675)5/2-
Quark core
dominance
MB cloud
dominance
MB dressing abs. values
(Argonne-Osaka ).
E. Santopinto and M. M. Giannini,
PRC 86, 065202 (2012).
V.I.Mokeev, Meeting January 26 2015, Hall-B at JLAB
I.G.Aznauryan, V.D.Burkert,
arXiv: 1412.1296[nucl-th]
N* Structure at High Photon Virtualities in Exploration of Strong Interaction
CLAS12 is the only facility foreseen in the world capable of determining electrocouplings of all prominent
N* at 5<Q2<12 GeV2. For the first time, almost direct access to the quark core at the distances where the
transition from quark-gluon confinement to perturbative QCD regime is expected.
D(1232)3/2+
Jones-Scadron convention
Dressed quark mass function
J. Segovia et al., arXiv:1408,2919 [nucl-th].
GM *
C.D. Roberts, Prog. Part. Nucl. Phys. (2008) 50.
N(1440)1/2 +
D.J. Wilson et al., Phys. Rev C85 (2012) 045205
DSEQCD.
I.G. Aznauryan & V.D. Burkert, Phys. Rev. C85
(2012) 055202 LF QM.
JLAB : Np
CLAS12 projected
CLAS12
area
Consistent results on quark mass function from
electrocouplings of different resonances at Q2 > 5 GeV2:
• will prove relevance and reliable access to this fundamental
ingredient;
• address two of the most challenging problems in the
Standard Model: the emergence of the dominant part of
hadron masses and quark-gluon confinement .
V.I.Mokeev, Meeting January 26 2015, Hall-B at JLAB
DSEQCD :
(quark core
only)
Light Front
Quark Model
(quark core & MB cloud)
constant quark mass.
running quark mass.
running quark mass
from DSEQCD.
Summary of the CLAS Data on Exclusive Meson
Electroproduction off Protons in N* Excitation Region
Hadronic final
state
Covered
W-range, GeV
Covered Q2range, GeV2
Measured
observables
C
p+n
1.1-1.38
1.1-1.55
1.1-1.7
0.16-0.36
0.3-0.6
1.7-4.5
ds/dW
ds/dW
ds/dW, Ab
p0p
1.1-1.38
1.1-1.68
1.1-1.39
0.16-0.36
0.4-1.8
3.0-6.0
ds/dW
ds/dW, Ab,At,Abt
ds/dW
hp
1.5-2.3
0.2-3.1
ds/dW
K+L
thresh-2.6
1.40-3.90
0.70-5.40
ds/dW
P0, P’
K+S0
thresh-2.6
thresh-2.6
1.40-3.90
0.70-5.40
ds/dW
P’
p+p-p
1.3-1.6
1.4-2.1
0.2-0.6
0.5-1.5
Nine 1-fold
differential
cross sections
•ds/dW-CM angular
distributions
•Ab,At,Abt-longitudinal
beam, target, and
beam-target asymmetries
•P0 P’ –recoil and
transfered polarization
of strange baryon
Almost full coverage
of the final hadron
phase space in
pN, p+p-p, hp, and KY
electroproduction
The data are
available in the
CLAS Physics
Data Base:
http://depni.sinp.msu.ru/cgi-bin/jlab/db.cgi
V.I.Mokeev, Meeting January 26 2015, Hall-B at JLAB
Extension of the CLAS Np data towards high Q2
The structure functions dsU/d(-cos(qp)), dsTT/d(-cos(qp)), dsTL/d(-cos(qp)) for p+n exclusive
electroproduction are currently available at W<2.0 GeV and for upper values of Q2 from 4
to 5 GeV2 . K.Park et al., (CLAS Collaboration) arxiv1412.0274[nucl-exp].
V.I.Mokeev User Group Meeting June 18 2008
Extension of the CLAS Np data towards high Q2
V.I.Mokeev User Group Meeting June 18 2008
Extension of the CLAS Np data towards high Q2
V.I.Mokeev User Group Meeting June 18 2008
Example of K+L data from the CLAS at high Q2
V.I.Mokeev User Group Meeting June 18 2008
Example of K+L from the CLAS at high Q2
V.I.Mokeev User Group Meeting June 18 2008
Example of K+S0 data from the CLAS at high Q2
V.I.Mokeev User Group Meeting June 18 2008
Example of K+S0 data from the CLAS at high Q2
V.I.Mokeev User Group Meeting June 18 2008
Extension of the CLAS p+p-p Electroproduction Data
R.W.Gothe,
G.V.Fedotov,
USC
E.L. Isupov, K.Hicks
MSU/Univ. of Ohio
Fully integrated p+p-p electroproduction cross
sections off protons
• Nine 1-fold differential cross sections are
available In each bin of W and Q2 shown in
the plots (see next slide).
• Resonance structures are clearly seen at
W ~1.5 GeV and ~1.7 GeV at 0.4< Q2< 5.0 GeV2
(red lines) .
Analysis objectives:
• Extraction of gvNN* electrocouplings and pD ,
rp decay widths for most N*s in mass range up
to 2.0 GeV and 0.4< Q2< 5.0 GeV2 within the
framework of JM-model.
• Exploration of the signals from 3/2+(1720)
candidate-state (M.Ripani et al., Phys. Rev. Lett
91, 022002 (2003)) with a goal to achieve decisive
conclusion on the state existence and structure.
• First results on electrocouplings of high-lying
(MN*>1.6 GeV) orbital nucleon excitations and
high-lying parity partners.
V.I.Mokeev, Meeting January 26 2015, Hall-B at JLAB
The CLAS Data on p+p-p Differential Cross Sections and their Fit
within the Framework of Meson-Baryon Reaction Model JM
• In each bin of W & Q2 shown in prev. slide similar nine 1-fold diff cross sections are available.
• Extraction of pD and rp contributions to all differential cross section can be done within the framework of the JM
model (see next slide).
M.Ripani et al, PRL 91 (2003), 022002
G.V.Fedotov et al, PRC 79 (2009), 015204
full JM calc.
p-D++
p+D0
2p direct
V.I.Mokeev, Meeting January 26 2015, Hall-B at JLAB
rp
p+D013(1520)
p+F015(1680)
JM Model Analysis of the p+p-p Electroproduction
Major objectives: extraction of gvNN* electrocouplings and pD, rp decay widths.
g
p-
g
p-/+
p+ =
p
p’
p
p
g
p-
g
D++/0 (1232)P33, N0 (1520)D13,
D++ (1600)P33, N0(1680)F15
p’
p-, p+, …
•N* contribute to pD
and rp channels only.
r,s
p+
+
p
•seven meson-baryon
channels and direct
p+p-p production.
+
p+, p-, …
p’
p
•unitarized Breit-Wigner
ansatz for resonant
amplitudes.
p’,p’, …
•V.I.Mokeev, V.D. Burkert, et al., (CLAS Collaboration) Phys. Rev. C86, 035203 (2012).
•V.I.Mokeev, V.D. Burkert , et al., Phys. Rev. C80, 045212 (2009).
V.I.Mokeev User Group Meeting June 18 2008
14
Needed development of the reaction models
•
Modelling of amplitudes other than photon-proton s-channel resonance contributions to exclusive
Np, KY, pD, rp electroproduction at photon virtualities up to 12 GeV2 and W from minimal possible
values in the area of W<2.0 GeV to 5.0 GeV (the region of W<3.0 GeV represents the area of interest
for the N* physics) accounting for:
a) hard processes in terms of diagrams with factorized explicit quark degrees of freedom;
b) relevant soft contributions in terms of parameterized meson-baryon degrees of freedom.
•
Adjustment of the reaction model parameters to all available observables combined as the test of
approach reliability
•
Region of hand-bag diagram applicability:
experience for Np rp, wp exclusive electroproduction: W>3.0 GeV at Q2~4.0 GeV2
W  W thrsh
x
B
 xthresh
 W
2
+Q
x
2
b

Q
2
2 M
Q
2
xb  2 2
2M
W +Q
2
Increase of Q gives rise to increase of Wthresh
Question: What is the W area of hand-bag diagram applicability at 5.0<Q2<12.0 GeV2?
If Wthresh> 5.0 GeV, the proposed reaction model development is of interest for both N* physics
and DVMP
V.I.Mokeev User Group Meeting June 18 2008
Back -up
V.I.Mokeev, Meeting January 26 2015, Hall-B at JLAB
Definition of gvNN* electrocouplings and basics for their extraction from
the data on exclusive meson electroproduction off nucleons
e’
Resonant amplitudes
Non-resonant amplitudes
p, h, pp,..
γv
e
N*,△
*
N’
N
p, h, pp,..
+
N’
N
•A1/2(Q2), A3/2(Q2), S1/2(Q2)
or
•G1(Q2), G2(Q2), G3(Q2)
or
•GM(Q2), GE(Q2), GC(Q2)
N*’s photo-/electrocouplings gvNN* are defined See details in:
at W=MN* through the N* electromagnetic
I.G.Aznauryan and
V.D.Burkert, Progr.
decay width g :
2
Part. Nucl. Phys.
2 N
2
2
67, 1 (2012).
gr
q
g  p
M
(2 J r + 1) M N *
A
1/ 2
+
A
3/ 2

• Separation of resonant/non-resonant contributions within the framework of reaction
models; Breit Wigner ansatz for parameterization of resonant amplitudes; fit of
resonance electroexcitation and hadronic parameters to the data.
• Consistent results on gvNN* electrocouplings from different meson electroproduction
channels and different analysis approaches demonstrated reliable extraction of N*
parameters.
V.I.Mokeev, Meeting January 26 2015, Hall-B at JLAB
The Approaches for Extraction of gvNN* Electrocouplings from Np
Exclusive Electroproduction off Protons
Unitary Isobar Model (UIM)
The Model based on fixed-t
Dispersion Relations (DR)
p
•the real parts of invariant Np
electroproduction amplitudes are
computed from their imaginary
parts employing fixed-t dispersion
relations;
•the imaginary parts of the Np
electroproduction amplitudes at
W>1.3 GeV are dominated by
resonant parts and were computed
from N* parameters fit to the data.
p
N
w,r,p
N
pp
pN
N
N
I. G. Aznauryan, Phys. Rev. C67, 015209 (2003), I.G.Aznauryan,
V.D.Burkert, et al. (CLAS Collaboration), PRC 80. 055203 (2009).
V.I.Mokeev, Meeting January 26 2015, Hall-B at JLAB
p
p+
Fits to gp→p+n Differential Cross Sections and
Structure Functions
Q2=2.44
GeV2
ds/dWp
Q2=2.05 GeV2
DR
DR w/o P11
UIM
Legendre moments Dl (l=0,1,2) from
various structure functions
V.I.Mokeev, Meeting January 26 2015, Hall-B at JLAB
DR
UIM
gvNN* Electrocouplings of Low-Lying Resonances
CLAS data:
p+p-p
Np
2012
2009
S1/2
N(1440)1/2+
p+p-p
prelim.
A1/2
N(1440)1/2+
A3/2
N(1520)3/2-
Consistent values of low-lying resonance
electrocouplings determined in independent
analyses of Np and p+p-p exclusive channels
strongly support:
• reliable electrocoupling extraction;
• capabilities of the reaction models to obtain
resonance electrocouplings in independent
analyses of Np and p+p-p electroproduction
channels.
V.I.Mokeev, Meeting January 26 2015, Hall-B at JLAB
Quark Core in the Structure of N(1440)1/2+
DSEQCD evaluation (D.J.Wilson, et al, Phys. Rev.
C85, 025205 (2012)) :
•Simplified contact interaction generates momentum
independent quark mass.
g D ( p - q)   
2
A1/2
approximation of
momentum independent quark mass is
applicable
4p  IR
m
2
G

IR
4p
m
 0.93
bare
q
m
G
 0.8GeV
 0.007GeV  mq
dressed
 0.368GeV
•Account for non-perturbative generation of dressed
quark mass.
Quark core contribution:
from DSEQCD.
from Np hadro-, photoand electroproduction
experimental data
(Argonne-Osaka model)..
DSEQCD expectations are consistent with
quark core contributions inferred from the
experimental data at Q2<2.0 GeV2
Future DSEQCD evaluations with realistic qqinteraction and running quark mass are of particular
importance to extend based on QCD predictions for
quark core contributions at higher Q2.
V.I.Mokeev, Meeting January 26 2015, Hall-B at JLAB
Quark Core & Meson-Baryon Cloud in the Structure of N(1440)1/2+
Advanced Light Front model (I.G. Aznauryan and
V.D, Burkert Phys. Rev. C85, 055202 (2012)):
• the contributions from three dressed quarks in the first
radial excitation and meson-baryon cloud are taken into
account;
•the model employs momentum dependent dressed
quark mass function from DSEQCD .
A1/2
Quark core from DSEQCD
with momentum independent
quark mass.
Quark core and MB cloud
from advanced LF quark
model with running quark
mass.
Combined contribution from inner quark core
and external meson-baryon cloud to the
N(1440)1/2+ structure in entire area of photon
virtualities covered by measurements Q2<5.0
GeV2 .
Better data description at high Q2 achieved
in the LF quark model offer an evidence
for running quark mass.
V.I.Mokeev, Meeting January 26 2015, Hall-B at JLAB
V.D.Burkert,
et al., PRC
67, 035204
(2003).
N* hadr. coupl.
M.Dugger,
are varied
et al., PRC
fixed D(1700)3/279,065206
hadr. couplings
(2009).
A1/2*1000 GeV-1/2
Preliminary D(1700)3/2- electrocouplings from the p+p-p CLAS data
Npp CLAS
Np Q2=0,
Δ(1700)3/2Np world
preliminary
CLAS
BF(Npp): 80-90%
A1/2
• They were determined varying both
electrocouplings and pD , rp hadronic decay
widths of all excited states contributing to
the third resonance peak.
Computed from N(1520)3/2- and N(1535)1/2electrocouplings within the SQTM approach:
I.G. Aznauryan and V.D. Burkert,
Progr. Nucl. Part. Phys. 67, 1 (2012).
V.I.Mokeev, Meeting January 26 2015, Hall-B at JLAB
A3/2*1000 GeV-1/2
• Studies of p+p-p electroproduction for the first
time provided accurate information on D(1700)3/2electrocouplings.
A3/2
Signals from N* states in the CLAS KY electroproduction data
D.Carman, private communication
ds
ds
 {
+
}
l
dq KT
dq K L
C 
P ( z )d (- z )
l
Q2=1.8 GeV2
Q2=2.6 GeV2
3/2 - 5/2(1950)
Q2=3.45 GeV2
KL
z  cos (q K )
the structures in Wdependencies of Cl –
moments at the same Wvalues in all Q2-bins are
consistent with the
contributions from
resonances of spinparities listed in the plots
1/2 +3/2+
(1850)
1/2+3/2+
(2000)
reaction model(s) are needed
for extraction of N* parameters
from KY electroproduction
KS
KS
3/2-5/2(2050)
V.I.Mokeev, Meeting January 26 2015, Hall-B at JLAB
W GeV
Transition N-P11(1440) form factors in LQCD
Includes the quark loops in the sea , which are
critical in order to reproduce the CLAS data at Q2<1.0 GeV2
A1/2, S1/2 => F1*, F2*
H.W. Lin and S.D. Cohen, arXiv:1108.2528
Mπ = 390, 450, 875 MeV
L box =3.0, 2.5, 2.5 f
CLAS data
•Exploratory LQCD results provide reasonable description of the CLAS data from the QCD
Lagrangian.
•Prospects for LQCD evaluation with improved projection operators, approaching physical
mp in the box of appropriate size.
V.I.Mokeev, Meeting January 26 2015, Hall-B at JLAB
Evidence for chiral symmetry breaking from Q2-evolution of
the ground state and S11(1535) parity partner form factors
-F1, F1*
In chiral symmetry limit:
- F 1 (Q )  (- Q ) G1 (Q )  F 1 (Q );
2
2
F 2 (Q )  2
2
(M + m ) m

2
*
G (Q )  F (Q );
2
*
2
2
2
1/2 +  1/2 - transitio n current :
1
J   (- Q g  - q g q ) G (Q ) - 2 ( M

2
2
1
+m
) i s  q G (Q )
2
2
M,m are S11(1535) and proton masses, k= 1.79
F1*, F2* p→S11(1535) form factors from
the CLAS data
F2, F2*
parameterization of elastic Dirac F1 and
Pauli F2 form factors
Evaluation of F1* and F2* starting
from QCD within the framework of
Light Cone Sum Rule & LQCD.
V.Braun et al., Phys. Rev. Lett., 103,
072001 (2009) .
Update: LCSR at NLO is in progress
J.Rohrwild, priv. com.
V.I.Mokeev, Meeting January 26 2015, Hall-B at JLAB