Transcript Combined analysis of recent CLAS data on 2-p photo

Studies of N* Structure from the CLAS
Meson Electroproduction Data
M. Ripani,
INFN Genova
MENU 2013 Conference
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
N,N* quark core
Studies of the N*-Structure in Exclusive Meson Electroproduction
Our experimental program seeks to determine
gvNN* electrocouplings at photon virtualities up to 5.0 GeV2 for most of
the excited proton states through analyzing major meson electroproduction channels independently and in global multi- channel analyses.
This information is needed to study the evolution of relevant degrees of
freedom in N* structure with distance and to access the non-perturbative
strong interaction which generates N* states as bound systems of quarks
and gluons
(see I. G. Aznauryan et al., Int. J. Mod. Phys. E22, 133015 (2013)).
The non-perturbative strong interaction represents the most important
part of the Standard Model that we have yet to explore.
It is the only fundamental sector where relevant degrees of freedom
accessible in the measurements can be very different with respect to
those entered in the basic QCD Lagrangian.
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
Extraction of gvNN* electrocouplings from the data on exclusive
meson electroproduction off protons
e’
Resonant amplitudes
p, h, pp,..
γv
e
N*,△
*
N’
N
Non-resonant amplitudes
p, h, pp,..
+
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’
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
q gr
2
Part. Nucl. Phys.
2
2

MN


67, 1 (2012).
 A1 / 2
 g p ( 2  1)
A 3 / 2 

J
r
M
N*
• 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 demonstrate reliable extraction of N*
parameters.
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
CEBAF Large Acceptance Spectrometer
Torus magnet
6 superconducting coils
Large angle calorimeters
Lead/scintillator, 512 PMTs
Liquid D2 (H2)target +
g start counter; e minitorus
Gas Cherenkov counters
e/pi separation, 216 PMTs
Drift chambers
argon/CO2 gas, 35,000 cells
Electromagnetic calorimeters
Lead/scintillator, 1296 PMTs
Time-of-flight counters
plastic scintillators,
684 PMTs
The unique combination of the CEBAF continuous electron beam and the CLAS detector
makes Hall-B@JLAB the only facility operational worldwide, that is capable of measuring
unpolarized cross sections and polarization asymmetries of most exclusive meson
electroproduction channels with substantial contributions at W<3.0 GeV and Q2<5.0 GeV2.
V.I.Mokeev
User
Group
MeetingPeniscola,
June 18 2008
V.I.Mokeev,
NSTAR
2013
Workshop
Spain, May 27-30, 2013
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
1.1-1.40
1.1-1.55
1.1-1.7
0.15-0.40
0.3-0.6
1.7-4.2
ds/dW
ds/dW
ds/dW, Ab
p0p
1.1-1.40
1.1-1.7
1.1-1.7
0.15-0.40
0.4-0.7
0.75-6.0
ds/dW
ds/dW, Ab,At,Abt
ds/dW
hp
1.5-2.0
0.2-4.0
ds/dW
K+L
1.65-2.35
1.65-2.35
0.65-2.55
1.4-2.6
ds/dW
P’
K+S0
1.7-2.1
1.8-2.5
1.7-2.6
0.5-2.55
1.5-3.50
1.8-3.50
ds/dW
P’
ds/dW
1.3-1.6
1.4-2.1
0.2-0.6
0.5-1.5
p+p-p
•ds/dW-CM angular
distributions
•Ab,At,Abt-longitudinal
beam, target, and
beam-target asymmetries
•P’ –recoil 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:
Nine 1-fold
differential
cross sections
http://depni.sinp.msu.ru/cgi-bin/jlab/db.cgi
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
N* Electroexcitation in Exclusive Meson Electroproduction off Protons
Hadronic decays of prominent N*s at W<1.8 GeV.
State
Bran. Fract.
to Np.
Bran. Fract.
to Nh
Bran.Fract.
Nππ
Δ(1232)P33
0.995
N(1440)P11
0.55-0.75
0.3-0.4
N(1520)D13
0.55-0.65
0.4-0.5
N(1535)S11
0.48±0.03
D(1620)S31
0.20-0.30
N(1650)S11
0.60-0.95
N(1685)F15
0.65-0.70
0.30-0.40
Δ(1700)D33
0.1-0.2
0.8-0.9
N(1720)P13
0.1-0.2
> 0.7
CLAS data on yields of meson
electroproduction at Q2<4 GeV2
0.46±0.02
0.70-0.80
0.03-0.11
0.1-0.2
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
Approaches for Extraction of gvNN* Electrocouplings from the CLAS Exclusive
Meson Electroproduction Data
•
Analyses of different meson electroproduction channels independently:
 p+n and p0p channels:
Unitary Isobar Model (UIM) and Fixed-t Dispersion Relations (DR)
I.G.Aznauryan, Phys. Rev. C67, 015209 (2003).
I.G.Aznauryan et al., CLAS Coll., Phys Rev. C80, 055203 (2009).
 hp channel:
Extension of UIM and DR
I.G.Aznauryan, Phys. Rev. C68, 065204 (2003).
Data fit at W<1.6 GeV, assuming S11(1535) dominance
H.Denizli et al., CLAS Coll., Phys.Rev. C76, 015204 (2007).
 p+p-p channel:
Data driven JLAB-MSU meson-baryon model (JM)

V.I.Mokeev, V.D.Burkert et al., Phys. Rev. C80, 045212 (2009).
V.I.Mokeev et al., CLAS Coll., Phys. Rev. C86, 035203 (2012).
Global coupled-channel analyses of the CLAS/world data of pN, gvN → pN, hN, ppN, KL,
KS exclusive channels:
N. Suzuki, T. Sato, T.-S.H. Lee, Phys.Rev. C82 (2010) 045206
H. Kamano, T.-S. H. Lee, AIP Conf.Proc. 1432 (2012) 74-79
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
Fits to gVp→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
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
DR
UIM
The CLAS Data on pp-p Differential Cross Sections and their Fit
within the Framework of Meson-Baryon Reaction Model JM
G.V.Fedotov et al, PRC 79 (2009), 015204
1.30<W<1.56 GeV; 0.2<Q2<0.6 GeV2
full JM calc.
p-D++
p+D0
2p direct
M.Ripani et al, PRL 91 (2003), 022002
1.40<W<2.30 GeV; 0.5<Q2<1.5 GeV2
rp
p+D013(1520)
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
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
p
+
p
•six 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
MeetingPeniscola,
June 18 2008
V.I.Mokeev,
NSTAR
2013
Workshop
Spain, May 27-30, 2013
10
Unitarized Breit-Wigner ansatz for resonant amplitudes
Developed based on approach: I.J.R.Aitchison, Nuclear Physics , A189 (1972), 417.
N*
Inverse of the JM unitarized N* propagator:
N*
-1
S  M N *  

2
- i(
 i
 i )
M N * M N *
-W
2
 
i
diagonal
N*
N*
Off-diagonal transitions incorporated into the
full resonant amplitudes of the JM model:
off-diagonal
S11(1535) ↔ S11(1650)
D13(1520) ↔ D13(1700)
3/2+(1720) ↔ P13(1700)
Full resonant amplitude of unitarized Breit-Wigner ansatz is consistent with restrictions
imposed by a general unitarity condition, as well as with the resonant Argonne-Osaka
ansatz in on-shell approximation.
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
NΔ Transition Form Factors
Magnetic Dipole Form Factor
MesonBaryon
cloud
CLAS
Hall A
 Hall C
MAMI
Bates
Quadrupole Ratios
pQCD: REM → 1.0
pQCD: ~1/Q5
pQCD: RSM → const
bare quark core
No evidences for pQCD onset at Q2<7 GeV2
Successful description was achieved
taking into account meson-baryon
dressing and quark core
T. Sato and T-S. H. Lee, PRC 63, 055201 (2001).
The mechanisms of the
meson-baryon dressing
Quark core was well described by the relativistic
QM: B.Julia-Diaz et al., PRC 69, 035212 (2004).
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
G*M (Jones-Scadron)
Quark vs Meson-Baryon Degrees of Freedom in N→D Form Factors
Q2/mr2
Quark core contribution from DSEQCD:
J.Segovia, et al., arXiv:1305.0292[nucl-th].
G1 and G2 N→D f.f. from LF quark model:
I.G.Aznauryan, V.D.Burkert, Phys. Rev. C85,
055202 (2012).
Contact interaction. Non-perturbative mass generation:
quark core.
4p
2
g D  ( p - q )  
m
bare
q

 0 . 007 GeV 

m
m
G
dressed
q
meson-baryon cloud
from Argonne-Osaka
approach.
dressed G1 and G2 f.f.
IR
2
 0 . 368 GeV
contact interaction.
contact interaction & quark
anomalous magn. moment.
projection for quark running mass.
bare G*M inferred from exp. data within
Argonne-Osaka c.c. approach.
For the first time this quark model accounts
for momentum dependence of dressed
quark mass.
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
The P11(1440) Structure from the CLAS Electrocoupling Data
CLAS data:
pp-p
Np
2012
2009
pp-p
prelim.
S1/2
Light Front quark
models:
I.G.Aznauryan,
PRC 76, 025212
(2007).
A1/2
S.Capstick and
B.D.Keister, PRD
51, 3598 (1995).
Meson-Baryon dressing:
(absolute values)
B,Julia-Diaz et al., PRC
77, 045205 (2008).
• Consistent values of P11(1440) electrocouplings
determined in independent analyses of Np and p+p-p
exclusive channels strongly support reliable
electrocoupling extraction.
• The physics analyses of these results revealed the P11(1440) structure as a combined
contribution of: a) quark core as a first radial excitation of the nucleon 3-quark ground state
and b) meson-baryon dressing.
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
Quark Core vs Meson-Baryon Cloud in the Structure of P11(1440)
First evaluation of the quark core contribution
to the P11(1440) electrocouplings starting from
QCD Lagrangian within Dyson-Schwinger
Equations of QCD:
D.J.Wilson, et al, Phys. Rev. C85, 025205 (2012).
A1/2
•Poincare-covariant, symmetry preserving DSEQCD
evaluation.
•Account for quark mass/structure formation in dressing
of bare quark by gluon cloud.
•Simplified contact interaction generates momentum
independent quark mass.
4p
2
g D  ( p - q )  

IR
4p
 0 . 93
m
G


m
IR
2
G
 0 . 8 GeV
Consistent results on the quark core contribution from:
DSEQCD.
bare
dressed
global meson photo-, electro-, and
 0 . 368 GeV
m q  0 . 007 GeV  m q
hadroproduction data analysis
within EBAC/ Argonne-Osaka approach.
Measured dressed electrocouplings are substantially different from the estimated quark
core contribution. Different data analyses suggest sizable meson-baryon cloud at Q2<5.0
GeV2 which gradually decreases with Q2 .
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
gvNN* Electrocouplings of D13(1520) and S11(1535) Resonances
D13(1520)
A3/2
S11(1535)
A1/2
D13(1520)
A1/2
MB dressing abs. values
(EBAC/Argonne-Osaka)
M.Giannini,E.Santopinto, PRC
86, 065202 (2012).
S.Capstick, B..D.Keister , PRD
51, 3598 (1995).
hp CLAS, Hall-C
•a good agreement between the results from Np, Nh and p+p-p exclusive channels.
•access to the lowest orbital excitation of 3-q system and DCSB manifestation through
comparison of the ground and S11(1535) state structure (chiral partners).
•contributions from inner quark core and external meson-baryon cloud, which depends
substantially on the resonance quantum numbers.
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
High lying resonance electrocouplings from the pp-p CLAS data analysis
Np world
V.D.Burkert,
et al., PRC
67, 035204
(2003).
Npp CLAS
preliminary
Np Q2=0,
CLAS
M.Dugger,
et al., PRC
79,065206
(2009).
Δ(1700)D33
BF(Npp): 80-90%
A1/2
pp-p electroproduction channel provided first
preliminary results on S31(1620), S11(1650), F15(1685),
D33(1700) , and P13(1720) electrocouplings with good
accuracy.
computed from the data on D13(1520) and
S11(1535) electrocouplings within the
framework of SQTM approach:
I.G. Aznauryan and V.D. Burkert, Progr.
Nucl. Part. Phys. 67, 1 (2012).
Single quark electromagnetic current and SU(6) spin-flavor
symmetry play an important role in the structure
and electroexcitation of D13(1520), S11(1535), and D33(1700)
states.
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
A3/2
High lying resonance electrocouplings from the pp-p CLAS data analysis
MAID analysis of Np electroproduction
L.Tiator et al., Eur. Phys. J. Spec. Top.
198, 141 (2011).
N (1685)F15
A1/2
BF(Np): 65-70%
BF(Npp): 30-40%
The results from pp-p channel confirmed the previous
MAID analysis of Np electroproduction
Hypercentral constituent quark model by
M.M.Giannini, E.Santopinto, PRC 86,
065202 (2012).
Bethe-Salpeter Bonn model by
M.Ronninger, B.Ch.Metsch, EPJ
A49, 8 (2013).
Difference between the experimental results and QM
expectations is likely related to meson-baryon cloud
contributions.
Evaluations of meson-baryon cloud contributions
to electrocouplings of high mass resonances
are needed.
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
A3/2
High lying resonance electrocouplings from the pp-p CLAS data analysis
Hypercentral constituent quark
model by M.Giannini,E.Santopinto,
PRC 86, 065202 (2012).
D(1620)S31
Bethe-Salpeter Bonn model by
M.Ronninger, B.Ch.Metsch, EPJ
A49, 8 (2013).
• Only known N*-state with dominant longitudinal
electroexcitation at Q2>0.5 GeV2 .
• This feature is well reproduced within
the framework of hypercentral quark model.
•
•
Data on electrocouplings of most excited proton
states in mass range up to 1.8 GeV demonstrated
distinctive differences in the structure of
resonances of different quantum numbers.
The studies of the ground and all prominent excited
state structure combined are needed in order to
explore the mechanisms of the ground and N*-state
formation from quarks and gluons.
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
S1/2
A1/2
Conclusions and Outlook
•
High quality meson electroproduction data from the CLAS detector allowed us to
determine electrocouplings of P33(1232), P11(1440), D13(1520), and S11(1535) resonances
from analyses of Np and Nh channels at Q2<5.0 GeV2 and Q2 <4.0 GeV2 , respectively, as
well as from the p+p-p electroproduction at Q2<1.5 GeV2. Consistent values of gvNN*
electrocouplings from independent analyses of Np/Npp and Np/Nh channels confirmed
reliable extraction of these fundamental quantities.
•
Preliminary results on electrocouplings of S31(1620), S11(1650), F15(1680), D33(1700), and
P13(1720) resonances were obtained from analysis of p+p-p electroproduction at 0.5<Q2
<1.5 GeV2 for the first time.
•
Analyses of the results on gvNN* electrocouplings revealed the N*-structure as internal
core of three constituent quarks surrounded by external meson-baryon cloud.
Resonances of different quantum numbers provided complementary information on the
N* structure. The data on electrocouplings of all prominent N*-states are needed.
•
Electrocouplings of most N*-states in mass range up to 2.0 GeV will be determined in
few years from independent analyses of Np and Npp electroproduction at photon
virtualities up to 5.0 GeV2.
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
Conclusions and outlook
•
The dedicated experiment on N* studies with the CLAS12 detector at the
largest photon virtualities ever achieved 5.0<Q2<12 GeV2 is scheduled for
the first year of running after completion of the Jefferson Lab 12 GeV
Upgrade Project.
•
The N* program with the CLAS12 detector opens up the prospects to
elucidate the emergence of >98 % of nucleon and N* masses from QCD.
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
Back up
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
CLAS12
Central
Detector
CLAS12 supports a
broad program in
hadronic physics.
Plans to study excited
baryons and mesons:
• Search for hybrid
mesons and baryons
• Spectroscopy of Ξ* , Ω• N* Transition form
factors at high Q2.
Forward
Detector
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
Resonance Transitions with the CLAS12
Resonance electrocouplings in
regime of quark core dominance can
be related to the running quark
masses and their dynamical structure.
quark mass (GeV)
accessible
at 6 GeV
12 GeV experiment E12-09-003 will
extend access to electrocouplings for all
prominent N* states in the range up to
Q2=12GeV2.
LQCD
DSE
accessible
at 12 GeV
P11(1440) A1/2
Light front quark model:
I.G.Aznauryan, V.D. Burkert,
PRC85, 055202 (2012).
DSEQCD :
contact interaction;
realistic QCD
interaction.
CLAS12 projected
Probe the transition from confinement to pQCD regimes, allowing us to explore how
confinement in baryons emerge from QCD and how >98 % of baryon masses are
generated non-perturbatively via dynamical chiral symmetry breaking.
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
• I. G. Aznauryan, A. Bashir, V. Braun,
S.J. Brodsky, V.D. Burkert, L.
Chang, Ch. Chen, B. El-Bennich,
I.C. Cloët, P.L. Cole, R.G. Edwards,
G.V. Fedotov, M.M. Giannini, R.W.
Gothe, F. Gross, Huey-Wen Lin, P.
Kroll, T.-S.H. Lee, W. Melnitchouk,
V.I. Mokeev, M.T. Peña, G.
Ramalho, C.D. Roberts, E.
Santopinto, G F. de Teramond, K.
Tsushima, D.J. Wilson
27 authors – 99 pages
•
Will be published in Int. J. Mod. Phys.
E22, 1330015 (2013).
http://arxiv.org/abs/1212.4891
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
Evidence for new N* states and couplings
State
N((mass)
JP
PDG 2010 PDG 2012
KΛ
KΣ
Nγ
N(1710)1/2+
***
(not seen in
GW
analysis)
***
***
**
***
N(1880)1/2+
**
**
*
**
N(1895)1/2-
**
**
*
***
***
***
**
***
N(1875)3/2-
***
***
**
***
N(2150)3/2-
**
**
***
**
N(1900)3/2+
N(2000)5/2+
N(2060)5/2-
**
*
***
**
*
**
**
***
Bonn-Gatchina Analysis – A.V. Anisovich et al., EPJ A48, 15 (2012)
Strong impact from the CLAS KY photoproduction data on the signala from new states
New states still need to be confirmed
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
Why studies of ground and excited nucleon states combined
are needed?
Di-quark
Jp
Ground
state
P11
½+(1440)
S11
½-(1535)
S11
½-(1650)
0-
51%
43%
1-
49%
57%
0+
77%
1+
23%
100%
Di-quark content of ground and N* states
from DSEQCD with vector x vector
interaction, C.D.Roberts et al.,
AIP Conf. Proc. 1432, 309 (2012).
N* spectrum and structure from LQCD,
J.J.Dudek, R.G.Edwards, Phys. Rev. D85,
054016 (2012).
• N* states of different quantum
numbers offer complementary
information on mechanisms of baryon
generation from quarks and gluons.
•N* electrocouplings allow us to
explore strong regime of QCD at
larger transverse distances with larger
s than the ground state form factors.
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
Impact of the Recent LQCD studies of N* Spectrum and Structure on
the N* Program with CLAS/CLAS12
J.J.Dudek, R.G.Edwards, Phys.
Rev. D85, 054016 (2012).
•each N* state with MN* <1.8 GeV
has partner in computed LQCD
spectrum, but level ordering is
not always consistent to the data
•wave functions of the low-lying
N* states dominate by 1-2 SU(6)
configurations, while the wave
function of high lying N*’s may
contain many SU(6) configurations
•presence of hybrid-N*s with
dominant contribution of hybrid
components at MN*>1.9 GeV marked by
Should be verified by experiment !
New direction in N* studies proposed in V.D.Burkert, arXiv:1203.2373 [nucl-ex]:
Search for hybrid N*-states looking for:
overpopulation of SU(6)-multiplet;
particular behavior of gvNN* electrocouplings, which reflects presence of the hybrid
component.
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
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 18 invariant Np
electroproduction amplitudes are
computed from their imaginary
parts employing model
independent 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).
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
p
p+
Resonant /non-resonant contributions from the fit of p+p-p
electroproduction cross sections within the JM model
W=1.51 GeV, Q2=0.43 GeV2
W=1.51 GeV, Q2=0.38 GeV2
Reliable isolation of the resonant cross sections is achieved
full cross sections
within the JM model
resonant part
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
non-resonant part
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.
M. Ripani, MENU 2013, Rome, September 30 – October 4, 2013
gvNN* Electrocouplings: A Unique Window into the Quark Structure
Meson-Baryon
Dressing
D13(1520)
P11(1440)
absolute meson-baryon
cloud amplitudes (EBAC)
quark core contributions
(constituent quark
models)
CLAS: Np
and Np/Npp combined
Data on gvNN* electrocouplings from E12-09-003 experiment (Q2 > 5 GeV2) will afford
for the first time direct access to the non-perturbative strong interaction among
dressed quarks, their emergence from QCD, and the subsequent N* formation.
V.I.Mokeev User Group Meeting June 18 2008
33
Anticipated N* Electrocouplings from data on Np & Npp electroproduction
P11(1440)
D13(1520)
S11(1535)
CLAS
Hall C
CLAS
CLAS
Open circles represent projections and all other markers the available results with the 6-GeV electron beam
 Examples of published and projected results obtained within 60d for three prominent
excited proton states from analyses of Np and Npp electroproduction channels. Similar
results are expected for many other resonances at higher masses, e.g. S11(1650), F15(1685),
D33(1700), P13(1720), …
 This experiment will – for the foreseeable future – be the only experiment that can
provide data on gvNN* electrocouplings for almost all well established excited proton states
at the highest photon virtualities ever achieved in N* studies up to Q2 of 12 GeV2.
V.I.Mokeev User Group Meeting June 18 2008
34