V.I.Mokeev NSTAR2007 at Bonn, September presented by V.I.Mokeev The studies of N* electrocouplings at various Q 2 elucidate relevant degrees of freedom in their structure and allow us to understand quark interactions, which are responsible for baryon formation from fundamental constituents. Promising way to study non-Abelian origin of strong interactions in non- perturbative domain, predicted in lattice simulations for quark binding in baryons. gluon self coupling in pQCD Lattice QCD calculation of gluon flux distribution in a system of 3 heavy quarks. Results from the analysis of the CLAS data on double charge pion electroproduction.

V.I.Mokeev NSTAR2007 at Bonn, September How to obtain reliable information on N* electrocouplings. Non-resonant amplitudes and N* hadronic couplings in various meson electroproduction channels are entirely different, while N* electrocouplings are expected to be the same. vv N  p   p  e e’ γvγv N N’N’ N*,△ A 3/2, A 1/2, S 1/2 Gm, Ge, Gc  Credible evaluation of N* electrocouplings should be achieved in successful description of all available observables in various electroproduction channels combined with common resonance electrocouplings.

V.I.Mokeev NSTAR2007 at Bonn, September CLAS data on meson electroproduction at Q 2 <4.0 GeV 2 Why the data on 1  /2  electroproduction mechanisms are vital for N* electrocoupling evaluation in any exclusive channel. Exclusive channels in  N scattering responsible for FSI in meson electroproduction 1  2  channels are major contributors. 1  2  channels are strongly coupled by FSI. W (GeV)

V.I.Mokeev NSTAR2007 at Bonn, September New opportunities for phenomenological studies of  electroproduction, offered by the CLAS data. Simplest measurements with unpolarized e - beam and p target, no use of polarization observables in the final state offer 9 independent single differential cross-sections in each (W,Q 2 ) bin. All these cross-sections are available from CLAS for the first time. Contributing mechanisms may be established from theirs manifestations in variety of observables JM approach..

V.I.Mokeev NSTAR2007 at Bonn, September JLAB-MSU model (JM) for 2-  electroproduction. 3-body processes: Quasi-2-body mechanisms included: All well established N*’s with  decays and 3/2 + (1720) candidate/P13(1720) with major decays to , seen in CLAS 2  data. Reggetized Born terms & effective FSI&ISI treatment. Extra  contact term. All well established N*’s with  p decays and 3/2 + (1720) candidate /modified P13(1720). Diffractive ansatz for non-resonant part &  -line shrinkage in N* region.

V.I.Mokeev NSTAR2007 at Bonn, September con’d 3-body processes: Quasi-2-body mechanisms included:  + D 0 13 (1520),  + F 0 15 (1685),  - P (1640) isobar channels, observed for the first time in CLAS data at W>1.65 GeV the amplitudes were described at phenomenological level (see ref. below). Direct 2  production in JM05. F 0 15(1685) (P ++ 33(1640)) (-)(-) (+)(+) Exchange processes, parameterized as: V.Mokeev, V.Burkert, et al., Proc. of NSTAR2005 Workshop p. 47

V.I.Mokeev NSTAR2007 at Bonn, September Direct 2  production mechanisms, established from analysis of the CLAS data: M.Ripani, V.Burkert, et.al., Phys.Rev. Lett. 91, (2003). W=1.49 GeV Q 2 =0.65 GeV 2 Q 2 =0.95 GeV 2 CLAS data fit under various assumptions on direct 2  production mechanisms: 3-body phase space the contributions from direct 2  mechanisms, described on previous slide exchange processes

V.I.Mokeev NSTAR2007 at Bonn, September Fit of CLAS 2  data on 3 invariant masses and  - angular distributions within the framework of JM05. , mcbn W, GeV Q 2 =0.65 Gev 2 Q 2 =0.95 Gev 2 Q 2 =1.30 Gev 2 Reasonable description of invariant mass and  - angular distributions was achieved in entire kinematics area covered by CLAS data. CLAS data M.Ripani, V.D.Burkert, et. al.

V.I.Mokeev NSTAR2007 at Bonn, September Fit of single differential cross-sections from recent CLAS 2  data (1.3<W<1.6 GeV, 0.25<Q 2 <0.6 GeV 2 ) within the framework of JM05 model. full  -  ++  +  0 2  direct Failure in description of  + and p angular distributions is related to the shortcomings in treatment of direct 2  production (dashed magenta lines). Preliminary Reasonable description of 4 differential cross-sections, studied previously, was achieved.

V.I.Mokeev NSTAR2007 at Bonn, September Modification of direct 2  production mechanisms. From JM05 to JM06. JM05JM06

V.I.Mokeev NSTAR2007 at Bonn, September Fit of CLAS data at low W and Q 2 (G.Fedotov, L.Elouadrhiri, et.al) within the framework of JM06 model.  -  ++  +  0 2  direct All significant mechanisms, contributing to ep→  -  + p channel at W<1.6 GeV and Q 2 <0.6 GeV 2 were established from the CLAS data analysis. Reasonable description of  i -angular distributions with model parameters fitted to 6 other diff. cross-sections offers compelling evidence for reliability of JM06 model. Preliminary JM06 full resonant part non-resonant part

V.I.Mokeev NSTAR2007 at Bonn, September Evaluation N* electrocouplings & isobar channel contributions from the CLAS 2  data fit. Q 2 -interv., GeV 2  2 /d.p < < <1.8 preliminary CLAS data of E experiment Preliminary  2 /d.p. for selected in fit cross-sections: N* electrocouplings and parameters for non-resonant mechanisms were varied. The  2 /d.p. were estimated from comparison between measured and calculated differential cross- sections.

V.I.Mokeev NSTAR2007 at Bonn, September Isobar channel contributions from CLAS data fit within the framework of JM06. CLAS data the contributions from all isobar channels CLAS data fit The data on isobar channel contributions are available for N* studies in the coupled channel analysis, under development at EBAC.

V.I.Mokeev NSTAR2007 at Bonn, September P11(1440) and D13(1520) electrocouplings determined from the CLAS data on 1  and 2  electroproduction. from analysis of CLAS 2  data within the framework of JM06 from analysis of 1  CLAS data combined analysis of 1  CLAS data P11(1440)D13(1520) CLAS 2  data provided compelling evidence for sign flip of P11(1440) A 1/2 electrocoupling. Electrocouplings obtained in two independent analyses of 1  and 2  channels are in reasonable agreement.

V.I.Mokeev NSTAR2007 at Bonn, September N * electrocouplings from exp. data & expectations from the models, accounting for quark degrees of freedom only. Ground p stateP11(1440) S.Capstick light cone (LC) model B.Metsch Bethe-Salpeter model I.Aznauryan LC model M.Giannini/ E.Santopinto hyper-centric CQM data on electromagnetic form factors for ground and excited nucleon states offer complementary information on baryon structure. various degrees of freedom in the structure of P11(1440), D13(1520) are surfaced at low and high Q 2 3q core 3q core +meson -baryon cloud +??

V.I.Mokeev NSTAR2007 at Bonn, September cont’d D13(1520) EBAC is developing coupled channel approach to disentangle meson- baryon dressing and “bare” quark core contributions to N* electrocouplings. After 12 GeV Upgrade CLAS12 will be only facility foreseen worldwide, capable to study electrocouplings for full spectrum of N*’s at Q 2 from 5.0 to 10 GeV 2. 3q core 3q core +meson –baryon cloud +?? The contribution from quark core increases with Q 2. Data on N* electrocouplings at high Q 2 are needed to study quark interactions in baryons.

V.I.Mokeev NSTAR2007 at Bonn, September N* electrocouplings & mechanisms responsible for baryon formation. The contributions from quark models of baryon structure are needed. In particular: contributions from potential quark models, allowing us to relate N* electrocouplings to the binding potential and the interactions, responsible for 3q configuration mixing; contributions from the models, based on Bethe-Saltpeter formalism, which allow us, using the data on N* electrocouplings, to constrain/establish quark scattering amplitudes, dressed quark propagators and elucidate their connection to QCD within the framework Dyson-Schwinger equations; establish constraints, imposed by the data on N* electrocouplings to light cone wave functions (LCWF) for N*, and relate LCWF to QCD. (S.Brodsky hep-ph/ ) it will be important to have LQCD predictions for understanding of the results from N* phenomenology.

V.I.Mokeev NSTAR2007 at Bonn, September Conclusions and outlook. Analysis of the most comprehensive worldwide CLAS data on ep→  -  + p cross- sections, carried out with the framework of JM approach, allowed us to establish from successful data fit the mechanisms with significant contributions to this exclusive channel in N* excitation region at Q 2 from 0.2 to 1.5 GeV 2. The amplitudes/cross-sections of various isobar channels were determined from the fit of the CLAS 2  data. They will be used by EBAC for evaluation of N* electrocouplings in advanced coupled channel analysis of various exclusive channels combined. The resonant amplitudes in 2  electroproduction were isolated in the data fit. P11(1440) and D13(1520) electrocouplings at Q 2 from 0.2 to 0.6 GeV 2 were obtained for the first time from analysis of 2  electroproduction data. Extension of this analysis is in progress with a goal to obtained electrocuplings for almost all N*’s with M < 3.0 GeV at 0.3<Q 2 <5.0 GeV 2. Comparison of the CLAS data on P11(1440), D13(1520) electrocouplings with quark model expectations showed, that various degrees of freedom contribute to the structure of N*’s at low and high Q 2. Focused effort of baryon structure theory is needed to relate N* phenomenology to fundamental strong interaction mechanisms, responsible for baryon formation.

V.I.Mokeev NSTAR2007 at Bonn, September Back-up

V.I.Mokeev NSTAR2007 at Bonn, September Manifestation of direct 2  production mechanisms in recent preliminary CLAS data (G.Fedotov, L.Elouadrhiri, et.al.). W=1.49 GeV Q 2 =0.325 GeV 2 full calculations 2  direct production W=1.49 GeV Q 2 =0.425 GeV 2 W=1.46 GeV Q 2 =0.525 GeV 2 Direct 2  production mechanisms, initially established at 0.5<Q 2 <1.5 GeV 2, were also observed in recent CLAS data at 0.25<Q 2 <0.6 GeV 2. Preliminary

V.I.Mokeev NSTAR2007 at Bonn, September Further studies of N* electrocoupling from the CLAS data on 2  electroptoduction. Short term objective: evaluation of electrocouplings for all well established N*’s with M<2.0 GeV at 0.25<Q 2 <1.5 GeV 2 from E93-006,E data within the framework of JM06. Intermediate term objective: evaluation of electrocouplings for all well established N*, search for new N* in mass range W<3.0 GeV and 0.<Q 2 <5.0 GeV 2 from analysis of e1-6,e1e,g1c,g11 CLAS data. Update of JM06 is expected, implementing partonic degrees of freedom in combination with meson-baryon content. Final goal: comprehensive information on electrocouplings for all established N*’s as well as for possible new baryon states in entire N* excitation region and at photon virtualities from 0. to 5.0 GeV 2.

V.I.Mokeev NSTAR2007 at Bonn, September Very preliminary results on 2  electroproduction at high Q 2. Fully integrated 2  cross section at Q 2 from 4.5 to 5.2 GeV 2 Evidence for substantial N* contributions