1. V.I.Mokeev September 10 Meeting Reaction models for evaluation of  v NN* electrocouplings from the data on N  N  electroproduction and their extension toward photon virtualities up to 12 GeV 2 presented by V.I.Mokeev

2. V.I.Mokeev September 10 Meeting Major objective of the Meeting Determine the prospects for modeling of non-resonant N , N  electroproduction amplitudes at 1.1<W<2.0 GeV and Q 2 from 3.0 to 12 GeV 2, employing effective quark degrees of freedom. Ultimate goal: develop the tools for evaluation of  v NN* electrocouplings from the data of these exclusive channels at high Q 2 available from CLAS (3.0<Q 2 <5.0 GeV 2 ) and expected after 12 GeV Upgrade from new Hall B detector CLAS12 (3.0<Q 2 <12.0 GeV 2 ). Particular requirements of N* physics: describe the amplitudes of ALL possible helicities (trans. & long. photons); provide maximal coverage of the final hadron phase space. In particular, the models should describe the final hadron angular distributions in a full range of angles in order to determine electrocouplings for overlapping N*’s of different spins.

3. V.I.Mokeev User Group Meeting June 18 2008 3 Nucleon Resonance Studies with CLAS12 D. Arndt 4, H. Avakian 6, I. Aznauryan 11, A. Biselli 3, W.J. Briscoe 4, V. Burkert 6, V.V. Chesnokov 7, P.L. Cole 5, D.S. Dale 5, C. Djalali 10, L. Elouadrhiri 6, G.V. Fedotov 7, T.A. Forest 5, E.N. Golovach 7, R.W. Gothe* 10, Y. Ilieva 10, B.S. Ishkhanov 7, E.L. Isupov 7, K. Joo 9, T.-S.H. Lee 1,2, V. Mokeev* 6, M. Paris 4, K. Park 10, N.V. Shvedunov 7, G. Stancari 5, M. Stancari 5, S. Stepanyan 6, P. Stoler 8, I. Strakovsky 4, S. Strauch 10, D. Tedeschi 10, M. Ungaro 9, R. Workman 4, and the CLAS Collaboration JLab PAC 34, January 26-30, 2009 Approved for 60 days beamtime http://www.physics.sc.edu/~gothe/research/pub/nstar12-12-08.pdf. Argonne National Laboratory (IL,USA) 1, Excited Baryon Analysis Center (VA,USA) 2, Fairfield University (CT, USA) 3, George Washington University (DC, USA) 4, Idaho State University (ID, USA) 5, Jefferson Lab (VA, USA) 6, Moscow State University (Russia) 7, Rensselaer Polytechnic Institute (NY, USA) 8, University of Connecticut (CT, USA) 9, University of South Carolina (SC, USA) 10, and Yerevan Physics Institute (Armenia) 11 Spokesperson Contact Person*

4. V.I.Mokeev September 10 Meeting Physics objectives in the N* studies at Q 2 >3.0 GeV 2 Q 2 = 10 GeV 2 = (p times number of quarks) 2 = 10 GeV 2 → p = 1.05 GeV DSE: lines and LQCD: triangles explore the interactions between the dressed quarks, which are responsible for the formation of both ground and excited nucleon states. probe the mechanisms of light current quark dressing, which are responsible for >97% of nucleon mass. Approaches for theoretical analysis of N* electrocouplings: LQCD, DSE, relativistic quark models. Q 2 =10GeV 2 Combined analysis of the data on  v NN* electrocouplings and detailed information on the ground state structure from GPD and semi/inclusive DIS allow us:

5. V.I.Mokeev User Group Meeting June 18 2008 5 Theory Support Group V.M. Braun 8, I. Cloët 9, R. Edwards 5, M.M. Giannini 4,7, B. Julia-Diaz 2, H. Kamano 2, T.-S.H. Lee 1,2, A. Lenz 8, H.W. Lin 5, A. Matsuyama 2, C.D. Roberts 1, E. Santopinto 4,7, T. Sato 2, G. Schierholz 8, N. Suzuki 2, Q. Zhao 3, and B.-S. Zou 3 Argonne National Laboratory (IL,USA) 1, Excited Baryon Analysis Center (VA,USA) 2, Institute of High Energy Physics (China) 3, Istituto Nazionale di Fisica Nucleare (Italy) 4, Jefferson Lab (VA, USA) 5, University of Genova (Italy) 7, University of Regensburg (Germany) 8, and University of Washington (WA, USA) 9 Development of approaches that will be capable to relate phenomenological information on N* electrcocouplings at high photon virtualities to non perturbative strong interaction mechanisms, that are responsible for formation of ground and excited nucleon states from quark and gluons, and to study their emergence from QCD The current plans are outlined in the paper: “Theory Support for the Excited Baryon Program at the JLAB 12 GeV Upgrade”, arXiv:0907.1901 [nucl-th],[nucl-ex],[lat-ph], JLAB-PHY-09-993.

6. V.I.Mokeev User Group Meeting June 18 2008 6 How N* electrocouplings can be accessed vv N  p   p  e e’ γvγv N N’N’ N*,△ A 3/2, A 1/2, S 1/2 G M, G E, G C  Consistent results on N* electrocouplings obtained in analyses of major meson electroproduction channels πN, and ππN with entirely different non-resonant amplitudes will show that they are determined reliably. Advanced coupled-channel analysis methods are being developing at EBAC: B.Julia-Diaz, T-S.H.Lee et al., PRC76, 065201 (2007);B.Julia-Diaz, et al., arXiv:0904.1918[nucl-th]. Isolate the resonant part of production amplitudes by fitting the measured observables within the framework of reaction models, which are rigorously tested against data. N* electrocouplings can then be determined from resonant amplitudes under minimal model assumptions. N γvγv  N’N’ + Non-resonant amplitudes. *

7. V.I.Mokeev September 10 Meeting Meson-baryon vs Quark contributions in NΔ Transition Form Factor – G M. EBAC analysis. the quark-core contribution is dominant at Q 2 >5.0 GeV 2  One third of G * M at low Q 2 is due to contributions from meson–baryon (MB) dressing: Data from exclusive π 0 production bare quark core Q 2 =5GeV 2

8. V.I.Mokeev September 10 Meeting Meson-baryon dressing / Quark core contributions in the A 1/2 electrocouplings of the P 11 (1440) & D 13 (1520) states. Estimates from EBAC for the MB dressing (absolute values): B.Julia-Diaz et al., PRC 76, 5201 (2007). P 11 (1440)D 13 (1520) Light Front quark model by I.Aznauryan hypercentric - quark model by M.Giannini Contribution from dressed quarks increases with Q 2 and is expected to be dominant at Q 2 >5.0 GeV 2. Quark degrees of freedom could play an important role in non resonant amplitudes at Q 2 >5.0 GeV 2. Therefore, the reaction models accounting for relevant quark degrees of freedom are of particular interest for extraction of  v NN* electrocouplings at Q 2 >5.0 GeV 2.

9. V.I.Mokeev September 10 Meeting N  CLAS data at low & high Q 2 Observable [GeV 2 ] Number of Data points dσ/dΩ(π 0 ) 0.35-1.631 018 dσ/dΩ(π + ) 0.25-0.65 1.7-4.3 13 264 33 000 Ae(π0)Ae(π0) 0.40 0.65 956 805 Ae(π+)Ae(π+) 0.40 0.65 1.7 - 4.3 918 812 3 300 dσ/dΩ(η) 0.375 0.750 172 412 Number of data points > 83,000, W < 1.7 GeV Low Q 2 results: I. Aznauryan et al., PRC 71, 015201 (2005); PRC 72, 045201 (2005); High Q 2 results on Roper: I. Aznauryan et al., PRC 78, 045209 (2008). Prelim. high Q 2 results on D 13 (1520), S 11 (1535): V.Burkert, AIP Conf.Proc. 1056, 248 (2008). full data set in: http://clasweb.jlab.org/physicsdb/

10. V.I.Mokeev September 10 Meeting Unitary Isobar Model (UIM) for N  electroproduction Final-state  N rescattering was taken into account through the K-matrix approximation I. Aznauryan, Phys. Rev. C67, 015209 (2003) ++ Non-resonant contributions were described by gauge invariant Born terms: pole/reggeized meson t-channel exchange; s- and u-nucleon terms.  n + +

11. V.I.Mokeev September 10 Meeting Fixed-t Dispersion Relations for invariant Ball amplitudes (Devenish &Lyth) Dispersion relations for 6 invariant Ball amplitudes: 17 UnsubtractedDispersion Relations 1 Subtracted Dispersion Relation γ*p→Nπ (i=1,2,4,5,6)

12. V.I.Mokeev September 10 Meeting Fits to   n diff. cross sections & structure functions DR UIM DR w/o P11 DR UIM Q 2 =2.44 GeV 2 Q 2 =2.05 GeV 2

13. V.I.Mokeev September 10 Meeting     p  electroproduction data from CLAS The measurements with an unpolarized e - beam onto a proton target offer nine independent differential cross sections in each (W,Q 2 ) bin.. Number data points > 8200 1.3 < W < 2.1 GeV ; 0.25 < Q 2 < 1.5 GeV 2 M. Ripani et al., PRL,91, 022002 (2003); G. Fedotov et al., PRC 79, 015204 (2009).

14. V.I.Mokeev User Group Meeting June 18 2008 14 JLAB-MSU meson-baryon model (JM) for N  electroproduction. 3-body processes: Isobar channels included: All well established N*s with   decays and 3/2 + (1720) candidate, seen in CLAS 2  data. Reggeized Born terms with effective FSI & ISI treatment. Extra  contact term. All well established N*s with  p decays and 3/2 + (1720) candidate. Diffractive ansatz for non-resonant part and  -line shrinkage in N* region.  -  ++ pp

15. V.I.Mokeev User Group Meeting June 18 2008 Born diagrams in  isobar channels 15

16. V.I.Mokeev User Group Meeting June 18 2008 16 Evidence for extra contact terms in     isobar channel. full calcu- lations extra contact term is taken off Parametrization of extra  contributions

17. V.I.Mokeev September 10 Meeting JLAB-MSU meson-baryon model (JM) for N  electroproduction. 3-body processes: Isobar channels included:  + D 0 13 (1520),  + F 0 15 (1685),  - P ++ 33 (1640) isobar channels; observed for the first time in the CLAS data at W > 1.5 GeV. Direct 2  production mechanisms without formation of unstable hadrons in the intermediate states were established in the CLAS N  data analysis for the first time and shown in the slides #18-22. They are most relevant at W<1.65 GeV, contributing <30 % to fully integrated N  cross sections. F 0 15(1685) (P ++ 33(1640)) (-)(-) (+)(+) V. Mokeev, V.Burkert, J. Phys. 69, 012019 (2007); V. Mokeev et al., arXiv:0809:4158[hep-ph], submitted to PRC All details of JM model may be found in:

18. V.I.Mokeev September 10 Meeting 18 Evidence for exchange processes in direct 2  production from the CLAS N  data W=1.49 GeV Q 2 =0.65 GeV 2 Q 2 =0.95 GeV 2 Fit of the CLAS data on  - angular distributions with direct 2  production mechanisms parameterized as : 3-body phase space contribution from direct 2  production, described by diagrams in slide # 19 exchange processes, shown in the slide # 19

19. V.I.Mokeev User Group Meeting June 18 2008 19 Direct 2  production mechanisms derived from the CLAS data on the final hadron invariant masses and   angular distributions The amplitudes were parameterized as:

20. V.I.Mokeev User Group Meeting June 18 2008 20 Description of invariant mass and angular distributions with direct 2  production mechanisms shown in the slide #19 full 2  direct The  + p,      - p mass and  - angular distributions were described successfully Failure in description of  + and proton angular distributions, revealed necessity to modify direct 2  production mechanisms.

21. V.I.Mokeev User Group Meeting June 18 2008 Direct 2  production mechanisms determined from analysis of all available CLAS data on N  electroproduction

22. V.I.Mokeev September 10 Meeting Description of the CLAS N  differential cross sections within the framework of JM model full JM calc.  -  ++ +0+0 2  direct pp  + D 0 13 (1520)  + F 0 15 (1685)

23. V.I.Mokeev September 10 Meeting Fully integrated  p→  +  - p cross sections: the contributions from various isobar channels and direct 2  production Q 2 =0.95 GeV 2 full calculation  -  ++ ++  +  D 13 (1520)  +  F 15 (1685)  p  +  P 33 (1640) direct 2  production

24. V.I.Mokeev September 10 Meeting Isobar channel cross sections derived from N  CLAS data band of differential cross sections calculated in JM model that are closest to experimental N  data, being determined under requirement :  2 /d.p.<  2 /d.p._max differential cross sections for contributing isobar channels:    ++ 00 may be used in development of reaction models W=1.51 GeV Q 2 =0.43 GeV 2

25. V.I.Mokeev September 10 Meeting P 11 (1440) electrocouplings from the CLAS data on N  /N  electroproduction N  preliminary NN Light front models: I. Aznauryan S. Capstick hybrid P 11 (1440) Good agreement between the electrocouplings obtained from the N  and N  channels: Reliable measure of the electrocouplings. The electrocouplings for Q 2 > 2.0 GeV 2 are consistent with P 11 (1440) structure as a 3-quark radial excitation of the nucleon. Zero crossing for the A 1/2 amplitude has been observed for the first time, indicating the importance of light-front dynamics.

26. V.I.Mokeev September 10 Meeting High lying resonance electrocouplings from N  CLAS data analysis N  CLAS preliminary N  world N  CLAS Q 2 =0 Δ(1700)D 33 N(1720)P 13 Preliminary

27. V.I.Mokeev September 10 Meeting Modeling of non-resonant  amplitudes at high Q 2 Evaluate the prospects for modeling of non-resonant  + n and  0 p amplitudes at 1.1<W<2.0 GeV and 3.0<Q 2 <12 GeV 2 employing effective quark degrees of freedom. Explore feasibility for description of observables in combined approaches, utilizing quark degrees of freedom for major contributions and phenomenological parameterization of the remaining parts. Using available N  electroproduction data from the CLAS at 3.0<Q 2 <5.0GeV 2, to study the possibilities of complete or partial replacement of meson-baryon degrees of freedom by quark degrees of freedom in reaction models for N* analyses. ( see full N  data sets in: http://clasweb.jlab.org/physdb/ )

28. V.I.Mokeev September 10 Meeting How we can extend reaction models for N  electroproduction toward 3.0<Q 2 <12 GeV 2 ? Analysis of the CLAS N  data clearly demonstrated our capabilities to establish all relevant mechanisms from their manifestation in observables and to achieve reliable separation between resonant/ non-resonant parts of amplitudes, if the contributions from mechanisms described within the framework of phenomenological parameterizations are less than 30 %. Substantial part of N  cross sections (>50%) should be described implementing relevant diagrams explicitly. Meson-baryon diagrams with typical cut-off parameters  ~ 1.0 GeV look questionable for description of N  electroproduction at Q 2 >5.0 GeV 2. They should be replaced, at least in part, by effective quark degrees of freedom that are relevant at these distance scales.

29. V.I.Mokeev September 10 Meeting Modeling of non-resonant  amplitudes at high Q 2 Evaluate the prospects for modeling of non-resonant amplitudes in a major isobar channel  v p      at 1.1<W<2.0 GeV and 3.0<Q 2 <12 GeV 2, employing relevant quark degrees of freedom. Priority#1 Study possibilities to implement quark degrees of freedom for non- resonant amplitudes in isobar channels of smaller cross sections:  v p  p;  v p   D 13 0 (1520);  v p   F 15 0 (1685) Priority#2 Could direct 2  production processes be interpreted in terms of quark degrees of freedom? Subject for discussions

30. V.I.Mokeev September 10 Meeting Back-up

31. V.I.Mokeev September 10 Meeting CLAS data on meson electroproduction at Q 2 < 4.0 GeV 2 Why N  /N  electroproduction channels are important N  /N  channels are the two major contributors in N* excitation region; these two channels combined are sensitive to almost all excited proton states; they are strongly coupled by  N→  N final state interaction; may substantially affect exclusive channels having smaller cross sections, such as  p,K , and K . Therefore knowledge on  electro production mechanisms is key for the entire N* studies at high photon virtualities with CLAS12 detector

32. V.I.Mokeev September 10 Meeting 32 Energy-Dependence of  + Multipoles for P 11, S 11 imaginary partreal part Q 2 = 0 GeV 2 Resonance contributions become more pronounced at higher Q 2. Q 2 = 2.05 GeV 2 I. Aznauryan (UIM)

33. V.I.Mokeev September 10 Meeting 33 Resonance signals in the CLAS data on N  electroproduction at 2.0< Q 2 <5.0 GeV2 Resonance structures are clearly seen in an entire Q 2 area covered by the CLAS data on N  electroproduction Resonances with masses above 1.65 GeV becomes more pronounced at high Q 2.

34. V.I.Mokeev September 10 Meeting 34 Resonance signals in N  electroproduction at high Q 2 from CLAS detector. Fully integrated N  cross sections at Q 2 from 4.5 to 5.2 GeV 2 Resonant contributions to N  exclusive channel remains substantial at high Q 2 and does not decrease considerably with Q 2. D13(1520) S11(1535) D33(1700),P13(1720) 3/2 + (1720),F15(1685)

35. V.I.Mokeev September 10 Meeting Projections for N* Transitions The projected electrocouplings were estimated based on expected counting rate and requirements for statistical accuracy of measured observables determined in analyses of the available data on N  and N  electroproduction CLAS published CLAS PRL subm. CLAS12projected CLAS published CLAS preliminay CLAS12 projected CLAS12 Fully unexplored area of 5.<Q 2 <12. GeV 2 will be covered for the first time. These distance scales correspond to a new regime in N* excitation

36. V.I.Mokeev User Group Meeting June 18 2008 36 W GeV Q 2 GeV 2 Kinematic Coverage of CLAS12 60 days L= 10 35 cm -2 sec -1,  W = 0.025 GeV,  Q 2 = 0.5 GeV 2 Genova-EG (e’,p     ) detected

37. V.I.Mokeev September 10 Meeting 37 Evidence for extra contact term in     isobar channel. full calculation: extra contact term: +0+0 W=1.76 GeV Q 2 =0.95 GeV 2 W=1.81 GeV Q 2 =0.95 GeV 2  p→  +  0 contributin:  - p mass, GeV   p mass, GeV d  /dM, mcbn/GeV on off on off extra contact term:

38. V.I.Mokeev User Group Meeting June 18 2008 38 Manifestation of  p→  - P 33 ++ (1640) and  p→  + F 15 (1685) isobar channels.  p→  + F 15 (1685)  p→   P 33 (1640) W=1.89 GeV Q 2 =0.95 GeV 2 full calculations  - P 33 ++ (1640)   F 15 0 (1685) Contributions from isobar channels:  - P 33 ++ (1640) and  + F 15 0 (1685) isobar channels off

39. V.I.Mokeev September 10 Meeting 39 Ground state and P11(1440) electrocouplings & quark model expectations 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 3q core 3q core +?? P11(1440) electrocouplings at Q 2 >2.0 GeV 2 are consistent with substantial contribution from 3-quarks in first radial excitation, while at Q 2 <0.6 GeV 2 additional contributions become evident.

40. V.I.Mokeev User Group Meeting June 18 2008 40 An additional contact terms in  channels needed to fit data.  2 = 1.64 GeV 2

41. V.I.Mokeev User Group Meeting June 18 2008 41 The amplitudes for  p  + F 0 15 (1685) and  p  - P ++ 33 (1600) channels.

42. V.I.Mokeev September 10 Meeting Input for N  /N  coupled channel analysis : partial waves of total spin J for non-resonant helicity amplitudes in  -  ++ isobar channel Born terms Extra contact terms J 1/2 3/2 5/2 Will be used for N* studies in coupled channel approach developing by EBAC.

43. V.I.Mokeev September 10 Meeting 43 Manifestation of  + D 0 13(1520) isobar channel in the CLAS N  data full calculation:  + D 0 13 (1520) channel on  + D 0 13(1520) contribution W=1.79 GeV  + D 0 13 (1520) channel off

44. V.I.Mokeev September 10 Meeting Resonant & non-resonant parts of N  cross sections as determined from the CLAS data fit within the framework of JM model full cross sections resonant part non-resonant part