1. A new & theoretical/experimental collaborative effort on baryon resonance extraction * Philip Cole Idaho State University April 22, 2009. *through a proposed NSF PIRE project 1 *through an overarching funding mechanism

2. Issues (1) They have very different contributions to the production background They have very different contributions to the production background. electron-positron collider electron-positron collider electron beam onto fixed target electron beam onto fixed target They separately have unique N* signatures They separately have unique N* signatures BES: J/   BN*  BBM (e.g. NNπ, NNη) BES: J/   BN*  BBM (e.g. NNπ, NNη) CLAS: N*  BM/BMM (e.g. Nπ/Nππ) CLAS: N*  BM/BMM (e.g. Nπ/Nππ) BES and CLAS datasets ──── 2

3. Issues (2) BES at BEPC has collected high statistics data on J/ψ production. Its decay into baryon-antibaryon channels offers a unique and complementary way of probing nucleon resonances (N*). CLAS at JLab has access to N* form factors at high Q 2, which is advantageous for the study of structure of nucleon resonances, guidance for the search for less-dominant The low-background BES results will be able to provide guidance for the search for less-dominant excited states at JLab. Several N* states have been seen at BES in the mass region of 2 GeV. M. Ablikim et al., (BES Collaboration), Phys. Rev. Lett. 97, 062001 (2006). existence of these new N* states be confirmed their properties to be precisely mapped out at various distances or Q 2 With the precision electron and photon beams afforded by JLab, not only would the existence of these new N* states be confirmed, but it would further allow for their properties to be precisely mapped out at various distances or Q 2. BES tells where to dig and CLAS has the steam shovel Coordination of efforts between BES and CLAS is timely 3

4. And the time has come; the talks have started… August 1-4, 2006: China-U.S. Symposium on Medium Energy Physics in Beijing. China. (Chinese Academy of Sciences) January 25-26, 2007: Workshop on Partial Wave Analysis and Dalitz Plot Analysis. IHEP. Beijing, China http://bes.ihep.ac.cn/conference/PWA/PWA%20workshop.htm October 13-15, 2008: JLab Workshop: “Electromagnetic N-N* Transition Form Factors,” (Organized by: V. Burkert, B. Julia-Diaz, R. Gothe, T.S. H. Lee, and V. Mokeev) http://conferences.jlab.org/EmNN/program.html http://conferences.jlab.org/EmNN/program.html which generated the whitepaper: JLAB-PHY-09-993, “Theory Support for the Excited Baryon Program at the JLab 12 GeV Upgrade,” Dec, 2008, 60 pp. See: https://www.jlab.org/~mokeev/white_paper/ https://www.jlab.org/~mokeev/white_paper/ (Editors: V. Burkert, T.-S. H. Lee, & V. Mokeev). April 19-22, 2009 NSTAR 2009 (This Conference) 4

5. OUTLINE  Introduction (Issues)  BES  CLAS  Theoretical Advances Partial-Wave Analysis (BES) Coupled-Channel Approach (EBAC) MAID SAID Bonn/Gatchina  CLAS12 approved experimental proposal  PIRE pre-proposal  Path Forward. 5

6. BES and BEPC 6

7. Baryon spectroscopy from J/  decays at BES/BEPC New mechanism for baryon production & an ideal isospin filter BingSong Zou MENU 07 7

8. 2. N* resonances observed in    N  N + c.c. BingSong Zou MENU 07 8

9.   Off-shell nucleon contribution N*(1440) N*(1520) N*(1535) N*(1650) N*(1675) N*(1680) ? BingSong Zou MENU 07 9

10. The new N*(2065) peak in  N mass spectrum J/    n N*(2065) with L=0 (small excess energy) limits its J P to be 3/2 + or 1/2 + (spin filter) PWA with event-based Maximum-Likelihood method  Both 3/2 + and 1/2 + are there. 10

11. Multiple Meson Final States Q: What about BN*  BBMM (+ c.c.)? A: BES III can sample this phase space for charged and neutral final-state particles. (cf. Yifang Wang’s talk on 19 April 2009) Complementary features to CLAS 11 ──

12. See: Physics at BES III. IHEP-Report-BES-III-2008-001-v2 (Yellow Book) Editors: Kuang-Ta Chao and Yifang Wang. (Yellow Book) arXiv:0809.1869v1arXiv:0809.1869v1 [hep-ex] 10 Sep 2008 12 3,000,000 (p     ) 650,000 (p   4,500 (p  With 500 Million J/  expected in April-June run 5x10 8 x B.R. 1,200,000 (p   ) 500,000 (p  0 ) 450,000 (K  Multiply the above numbers by 20 for 10 10 events!

13. 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  electroproduction mechanisms is key for the entire N* Program Therefore knowledge on  electroproduction mechanisms is key for the entire N* Program 13

14. CLAS and JLab 14

15. Electromagnetic Excitation of N*s vv N  p   p  e e’ γvγv N N’N’ N*,△ A 3/2, A 1/2, S 1/2 M l+/-, E l+/-, S l+/-  Measure the electromagnetic excitations of low-lying baryon states (<2 GeV) and their transition form factors over the range Q 2 = 0.1 – 7 GeV 2 and measure the electro- and photo-production of final states with one and two pseudo-scalar mesons. DOE Milestone 2012 15

16. Electromagnetic Excitation of N*s The experimental N* Program has two major components: 1) Transition form factors of known resonances to study their internal structure and the interactions among constituents, which are responsible for resonance formation. 2) Spectroscopy of excited baryon states, search for new states. Both parts of the program are being pursued in various meson photo- and electroproduction channels, e.g. Nπ, pη, pπ + π -, KΛ, KΣ, pω, pρ 0 using cross sections and polarization observables. 16

17. 17 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 various meson channels (e.g. πN, ηp, ππN) with entirely different non-resonant amplitudes will show that they are determined reliably Advanced coupled-channel analysis methods are being developing at EBAC: See: B.Julia-Diaz, et al., arXiv:0904,1918v1 [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. These N* electrocouplings can then be determined from resonant amplitudes under minimal model assumptions. N γvγv  N’N’ + Non-resonant amplitudes. 17

18. Primary objectives in our studies of N* structure with CLAS Our experimental program seeks to determine N-N* transition helicity amplitudes (electrocouplings) their evolution with photon virtualities for Q 2 < 5.0 GeV 2 for almost all excited proton states by analyzing single- and double-meson electroproduction channels combined, employ advanced coupled-channel approach developing by EBAC. This comprehensive information on Q 2 evolution of the N-N* electrocouplings will allow us to: determine the active degrees of freedom in N* structure at various distances; study the nonperturbative strong interactions which are responsible for  the ground and excited nucleon state formation,  and how they emerge from QCD. 18

19. P 11 (1440) electrocouplings from the CLAS data on N  /N  electroproduction N  NN Light front models: I. Aznauryan S. Capstick hybrid P 11 (1440) [Q 3 g] 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. Zero crossing for the A 1/2 amplitude has been observed for the first time, indicating an importance of light-front dynamics. 19

20. Resonance Analysis Tools Amplitude & multipole analysis (GWU-SAID, MAID) Phenomenological analysis procedures have been developed, e.g. unitary isobar models (UIM), dispersion relations (DR), that separate non-resonant and resonant amplitudes in single channels. PWA from BES/IHEP – BingSong Zou, Jian-Xiong Wang Dynamical coupled channel approaches for single and double pion analysis are being developed within the Excited Baryon Analysis Center (EBAC) effort. They are most important in the extraction of transition form factors for higher mass baryon states. 20 Nucleon resonances are broad and overlapping careful analyses of angular distributions for differential cross sections and polarization observables are needed

21. Coupled-channels picture of resonance excitation (EBAC) T=T= T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  T  The same N* resonance must be found in different reaction channels in a consistent way!  N  N  N  N*   N KΛ KΣ 21

22. EBAC strategy (summary) Electromagnetic N-N* form factors QCDQCDQCDQCD Lattice QCD Hadron Models Dynamical Coupled-Channels Analysis @ EBAC Reaction Data Bruno Juliá Díaz 22

23. Meson-baryon dressing vs Quark core contribution in NΔ Transition Form Factor – G M. EBAC analysis. Within the framework of relativistic QM [ B. Julia-Diaz et al., PRC 69, 035212 (2004 )], the bare-core contribution is very well described by the three-quark component of the wf.  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 core 23

24. Conclusions (so far on CLAS stuff) The CLAS Collaboration has developed phenomenogical approaches with the goal of determining N* electrocouplings from combined fits of measured observables in both the N  & N  electroproduction data. The CLAS Collaboration has developed phenomenogical approaches with the goal of determining N* electrocouplings from combined fits of measured observables in both the N  & N  electroproduction data. A good description of the CLAS data on N  electroproduction and differential cross sections in     p channel has been achieved, affording us to access the resonant parts of amplitudes, which are directly related to N* electrocouplings. A good description of the CLAS data on N  electroproduction and differential cross sections in     p channel has been achieved, affording us to access the resonant parts of amplitudes, which are directly related to N* electrocouplings. The consistent results extracted from these two channels strongly indicate a reliable electrocoupling measurement. The consistent results extracted from these two channels strongly indicate a reliable electrocoupling measurement. Comparison of the data on N* electrocouplings with quark model expectations in coordination with EBAC evaluations for MB cloud show that for Q 2 <1.0 GeV 2 both the MB cloud and quark core play an important role in the N* structure. Comparison of the data on N* electrocouplings with quark model expectations in coordination with EBAC evaluations for MB cloud show that for Q 2 <1.0 GeV 2 both the MB cloud and quark core play an important role in the N* structure. Contribution from the MB cloud decreases with Q 2, but can be still sizable at Q 2 5.0 GeV 2 quark degrees of freedom are expected to dominate Contribution from the MB cloud decreases with Q 2, but can be still sizable at Q 2 5.0 GeV 2 quark degrees of freedom are expected to dominate. 24

25. Highest priority recommendation in the DOE/NSF Nuclear Science Advisory Committee (NSAC) Long-Range Plan, 174 pages, Dec. 2007 Highest priority recommendation in the DOE/NSF Nuclear Science Advisory Committee (NSAC) Long-Range Plan, 174 pages, Dec. 2007. http://www.sc.doe.gov/np/nsac/docs/Nuclear-Science.High-Res.pdfhttp://www.sc.doe.gov/np/nsac/docs/Nuclear-Science.High-Res.pdf Recommendation I: We recommend completion of the 12 GeV CEBAF Upgrade at Jefferson Lab. The Upgrade will enable new insights into  the structure of the nucleon,  the transition between the hadronic and quark/gluon description of nuclei, and  the nature of confinement. JLab’s Future 25

26. Hadron Structure with e.m. Probes resolution of probe low high ,.. Allows to address central question: What are the relevant degrees-of-freedom at varying distance scale? q e.m. probe LQCD/DSE quark mass (GeV)     3-q core pQCD 3-q core+ MB cloud 26

27. Physics objectives in the N* studies with CLAS12 explore the interactions between the dressed quarks, which are responsible for the formation for both ground and excited nucleon states. probe the mechanisms of light current quark dressing, which is responsible for >97% of nucleon mass. Approaches for theoretical analysis of N* electrocouplings: LQCD, DSE, relativistic quark models. See details in the White Paper of EmNN* JLAB Workshop, October 13-15, 2008: http://www.jlab.org/~mokeev/white_paper/ 27 Need to multiply by 3p 2 to get the Q 2 per quark Q 2 = 12 GeV 2 Independent QCD Analyses Line: DSE Points: LQCD

28. Projections for N* Transitions For the foreseeable future, CLAS12 will be the only facility worldwide, which will be able to access the N* electrocouplings in the Q 2 regime of 5 GeV 2 to 10 GeV 2, where the quark degrees of freedom are expected to dominate. Our experimental proposal “Nucleon Resonance Studies with CLAS12” was approved by PAC34 for the full 60-day beamtime request. http://www.physics.sc.edu/~gothe/research/pub/nstar12-12-08.pdf. CLAS published CLAS PRL subm. CLAS12 projected CLAS published CLAS preliminay CLAS12 projected CLAS12 28

29. 29 CLAS12 Detector 29

30. 30 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 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* 30

31. 31 Theory Support Group V.M. Braun 8, I. Cloët 9, R. Edwards 5, M.M. Giannini 4,7, B. Juliá-Díaz 2, H. Kamano 2, T.-S.H. Lee 1,2, A. Lenz 8, H.W. Lin 5, A. Matsuyama 2, M.V. Polyakov 6, 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 JLab PAC 34, January 26-30, 2009 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, Ruhr University of Bochum (Germany) 6, University of Genova (Italy) 7, University of Regensburg (Germany) 8, and University of Washington (WA, USA) 9 Open invitation. List is open to any and all who wish to participate ! 31

32. Need Need to find the best way to theoretically extract the most pertinent observables from this huge database. Need Need a coordinated and dedicated effort between theorists and experimentalists to develop new and efficient analysis tools. Need Need complementary techniques for extracting these observables for extracting baryon resonances from BES and Jlab. Need Need an infusion of young talent to maintain the N* “lifeblood.” Need Need a partnership among experimentalists centered at CLAS and at BES and theorists working in BES and based in China and theorists working with the Excited Baryon Analysis Center at JLab. CLAS BES There is a huge amount of high-quality data streaming in from CLAS and BES J /   BN*  BBM(M) in BES is complementary to N*  BM/BMM (e.g, N π/ N ππ) in CLAS Coordination of efforts between BES and CLAS is timely ─ ─ And this collaborative work can lead to significant discovery potential 32

33. Partnership for International Research and Education (PIRE) We are seeking NSF PIRE support for a new U.S./China collaboration formed of experimentalists, theorists, and phenomenologists. 11 institutions in the U.S. and in the PRC with 18 PIs/senior personnel/ foreign collaborators for analyzing this torrent of data from CLAS and BES Many talented theorists:  China: Partial-Wave Analysis of excited baryons at the Institute for High Energy Physics in Beijing and at the Beijing Electron Positron Collider.  USA: Coupled-Channel Approach at Excited Baryon Analysis Center at JLab Many talented experimentalists We submitted a pre-proposal on Feb. 16, 2009 for $3M for this five-year program. We will hear word on invite-to-proposal stage by late May or early June. ~650 pre-proposals → ~75 invited → ~15 funded 33

34. List of Participants – PIRE: Nucleon Resonance Studies (Pre-Proposal) PI/CoPIs: PI and Program Manager  Philip L. Cole (PI and Program Manager, Associate Professor of Physics) Department of Physics, Idaho State University, Pocatello, ID 83209 First CoPI and Deputy Program Manager  Ralf W. Gothe (First CoPI and Deputy Program Manager, Professor of Physics) Steffen Strauch (CoPI, Associate Professor of Physics) Department of Physics and Astronomy, University of South Carolina, Columbia, SC 29208  Kyungseon Joo (CoPI, Associate Professor of Physics) Department of Physics, University of Connecticut, Storrs, CT 06269 Senior Personnel:  Volker D. Burkert ( Hall B Leader)  Latifa Elouadrhiri (Assistant Project Manager for the 12 GeV Upgrade – Hall B)  Victor I. Mokeev (Hall B Staff Scientist II) Thomas Jefferson National Accelerator Facility, Physics Division, Newport News, VA 23606  Tsung-Shung Harry Lee (Senior Physicist and Director of Excited Baryon Analysis Center – JLab) Physics Division. Argonne National Laboratory. Argonne, IL 60439  Debra M. Easterly 1 (Director of Research Development & Compliance, NSF ADVANCE Grant Project Director for ISU)  Angela V. Petit 2 ( Assistant Professor of English) 1 Office of Research, 2 Department of English, Idaho State University, Pocatello, ID 83209  Kevin Kelley 1 ( Professor of Physics)  Scott Galer 2 (Associate Professor of Chinese and Chair of Foreign Languages and Literatures) 1 Department of Physics, 2 Department of Foreign Languages and Literatures, Brigham Young University – Idaho, Rexburg, ID 83460 Foreign Collaborators: Chief Chinese Liaison  Qiang Zhao ( Chief Chinese Liaison, Professor of Physics and Group Leader of the Theory Division) Deputy Chinese Liaison  Bing-Song Zou ( Deputy Chinese Liaison, Professor of Physics and Director of the Theory Division) Theory Division, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, P.R. China  Cong-Feng Qiao (Executive Dean and Professor of Physics) College of Physical Sciences, Graduate School of the Chinese Academy of Sciences Beijing 100049, P.R. China  Xue-Qian Li (Professor of Physics) Physics Department, Nankai University, Tianjin 300071, P.R. China  Bi-Tao Hu (Vice Dean and Professor of Physics) The School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, P.R. China  Inna Aznauryan (Leading Staff Scientist) Yerevan Physics Institute – Yerevan State University, Yerevan, Armenia, 375036 34

35. Letter of Recommendation from Prof. T.D. Lee* * Nobel Prize in 1957, parity violation in the weak decay. 35

36. Message to take home. 36 Why N*s are important Why N*s are important. (quoted from Nathan Isgur 1,2 ) The first is that nucleons are the stuff of which our world is made. My second reason is that they are the simplest system in which the quintessentially nonabelian character of QCD is manifest. The third reason is that history has taught us that, while relatively simple, baryons are sufficiently complex to reveal physics hidden from us in the mesons ” 1 Workshop on Excited Nucleons and Hadronic Structure (2000). 2 Baryon Spectroscopy, E. Klempt and J.-M. Richard, arXiv:0901.2055v1[hep-ph]1 4 Jan 2009 We need to spread the word to lay and expert audiences alike that excited baryon research is indeed exciting and crucial to science.

37. Questions to the N* Community: 1. How best to coordinate efforts between JLab and IHEP? 2. How best to coordinate efforts between BES and CLAS? 3. How best to open and fund unique opportunities for students,students, postdoctoral researchers,postdoctoral researchers, senior experimentalists, andsenior experimentalists, and senior theoristssenior theorists. on collaborating between CLAS and BES on N* Physics? How to proceed – in a transformational way – so as to tackle the fundamental issue of what generates mass in the proton, say? 37

38. Path Forward We need overarching funding so that  Experimentalists from BES and CLAS can collaborate,  Theorists from EBAC and IHEP can collaborate, and  Open opportunities for young bright physicists on both sides of the Pacific to work on this problem. A grant from the Partnership for International Research and Education (PIRE) from the Office of International Science and Engineering of the National Science Foundation would offer this transformational opportunity. 38 We need to understand how strong interactions evolve from pQCD to the quark confinement regime in baryons. This can only be done by understandi ng N* structure.

39. Thanks to BingSong Zou (IHEP and BES) Victor Mokeev (JLab) for providing me their slides 39

40. Extra Slides 40

41. 1. Experimental observables – Starting point for PWA P 1, M 1 P 2, M 2 k 1, m 1 k 2, m 2 k n, m n Experimental distribution probability: W exp (k 1, …, k n ) ~ | M (k 1, …, k n ) | 2  (k 1, …, k n ) d  n (k 1, …, k n ) amplitude efficiency phase space various projections BingSong Zou PWA at BES Workshop 07 41

42. 2. PWA framework R1R1 R2R2 = + + …… M (k 1, …, k n ) = C 1 A R1 (k 1, …, k n ) + C 2 A R2 (k 1, …, k n ) + … W th (k 1, …, k n ; C 1,C 2, … ) PWA: fitting experimental data to get C 1,C 2, … Old fashion :  2 -fit to various projections Modern technique: event-based, multi-dimensional Maximum Likelihood fit to W exp (k 1, …, k n ) CERNLIB programs : FUMILI, MINUIT BingSong Zou PWA at BES Workshop 07 42

43. Some references : W.Rarita, J.Schwinger, Phys. Rev. 60, 61 (1941) E.Behtends, C.Fronsdal, Phys. Rev. 106, 345 (1957) S.U.Chung, PRD48, 1225 (1993); PRD57, 431 (1998) B.S.Zou, D.V.Bugg, Eur. Phys. J. A16, 537 (2003) for mesons B.S.Zou, F.Hussian, PRC67, 015204 (2003) for baryons Basic ingredients : (1)spin wave-function for single particle (2)orbital wave-function for two-particle system (3) g ,   (4) Breit-Wigner propagator, form factor BingSong Zou PWA at BES Workshop 07 43 3. Construction of PWA covariant tensor amplitudes

44. The first experiment “seeing” N*(1440) in  N mass spectrum BESII  MeV PDG06 M =  MeV BingSong Zou MENU 07 44

45. High-lying resonance electrocouplings from N  CLAS data analysis D 33 (1700)P 13 (1720) N  CLAS N  world N  world Q 2 =0 Analysis of the CLAS data provides first-time information on the electrocouplings for N*s that decay primarily to the N  final states The A 1/2 electrocoupling of P 13 (1720) decreases rapidly with Q 2. At Q 2 >0.9 GeV 2 |A 3/2 | > |A 1/2 |. Search for Q 2 regime where the helicity conserving A 1/2 amplitude of P 13 (1720) dominates and is important question for N* studies at high Q 2 45

46. 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: B.Juliá- Díaz 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 MB dressing effects have substantial contribution to low lying N* electrouplings at Q 2 <1.0 GeV 2 and gradually decrease with Q 2 ; Contribution from dressed quarks increases with Q 2 and are expected to be dominant at Q 2 >5.0 GeV 2. 46

47. 1. Fixing hadronic parameters 2. Good model to describe  N reactions at Q 2 = 0. What is needed for extracting electromagnetic N-N* form factors? Pure hadronic process; Determined from  N   N,  N,  N Pure hadronic process; Determined from  N   N,  N,  N Before analyzing eN  e’  N, e’  N, …, we need Determined from  N   N,  N,  N Determined from  N   N,  N,  N Critical for the model construction Starting point to explore Q 2 > 0 region Bruno Juliá Díaz 47

48. Coupled Channel Analysis (EBAC)  Pion-nucleon and two-pion-nucleon contributions to the non-resonant T matrix. T.-S. Harry Lee 48

49. List of the questions relating to the motivation of N* studies using an 11-GeV electron beam for probing photon virtualities from 5.0 to 10 GeV 2. proposed N* transition helicity amplitude data in the Q 2 region of 5.0 to 10 GeV 2 impact your theoretical approach 1.How will our proposed N* transition helicity amplitude data in the Q 2 region of 5.0 to 10 GeV 2 impact your theoretical approach and, in general, how will this data extend our overall understanding of strong interactions responsible in the formation of N*s? A set 7 Questions was sent to all theorists who attended the Workshop 49

50. Need for Theoretical Support Small exclusive channel cross sections, channel couplings due to unitary constraints can lead to strong distortions of amplitudes. Requires a complete and thorough coupled-channel analysis which includes all major channels with all attendant observables. The Excited Baryon Analysis Center (EBAC) was established in 2006 at JLab to provide theoretical support for the excited baryons experimental program. PWA efforts at BES 50

51. To justify this claim of being able to access quark-core degrees of freedom at high photon virtualities, we ask you to make estimates of the Q 2 -behavior of the two components, i.e. a) constituent quark core b) meson-baryon dressing of N-N* photon vertices, A 1/2 A 3/2 S 1/2 which contribute to the A 1/2, A 3/2, S 1/2 N-N* transition amplitudes: for the N* P 33 (1232), P 11 (1440), D 13 (1520), S 11 (1535), F 15 (1685), P 13 (1720), D 33 (1700)5.0 < Q 2 < 10 GeV 2 states: P 33 (1232), P 11 (1440), D 13 (1520), S 11 (1535), F 15 (1685), P 13 (1720), D 33 (1700) in the region 5.0 < Q 2 < 10 GeV 2. vv N  p   p  photon virtualities ranging from 5.0 to 10 GeV 2 meson-baryon dressing to the N-N* vertices are presumably small. probe will allow for effectively delineating the constituent quark-core configurations from other competing processes 2.We anticipate that by studying N* behavior at photon virtualities ranging from 5.0 to 10 GeV 2, it will give us access to resonance structure at distances, where the expected contributions from meson-baryon dressing to the N-N* vertices are presumably small. *Hence this probe will allow for effectively delineating the constituent quark-core configurations from other competing processes. γvγv N N*,△ A 3/2, A 1/2, S 1/2 M l+/-, E l+/-, S l+/- e e’ 51

52. How will the data on N-N* transition helicity amplitudes, obtained at 5.0 < Q 2 < 10 GeV 2, extend our knowledge on the binding potential and effective interactions responsible for 3-quark configuration mixing 3. How will the data on N-N* transition helicity amplitudes, obtained at 5.0 < Q 2 < 10 GeV 2, extend our knowledge on the binding potential and effective interactions responsible for 3-quark configuration mixing (i.e. OGE, OPE, instanton,…) within constituent quark models?  How will such data on N* electrocouplings at high Q 2 help us in getting access to light-cone wave functions of excited proton states and the associated currents?  What can we learn about the evolution constituent quark form factors?  What are the prospects of relating the constituent quark, covariant and Dyson-Schwinger models to the underlying QCD and, in turn, how will this data on N* electrocouplings at high Q 2 be useful in establishing these relations? 4. Is it possible or likely that data on N* electrocouplings at high Q 2 will afford us access to excited flux tubes as a possible active degree of freedom in the N* structure? And could this be used to study flux tube self-interactions ? 52

53. rapid risedressed-quark running mass 5.How does the rapid rise of the dressed-quark running mass impact the N-N* transition helicity amplitudes, as revealed from both the studies of the dressed-quark propagator within the framework of Dyson-Schwinger equations and from lattice calculations? How then may this running mass phenomenon be established in the studies of N* electrocouplings at high Q 2 ? 6. What are the prospects of having lattice calculations  which relate the underlying QCD data in N-N* helicity transition amplitudes at Q 2 up to 10 GeV 2 ?  And would such N* electrocoupling data be of significant benefit in making lattice calculations within this high Q2 regime, where the expected contributions from meson- baryon dressing of N-N* photon vertices become negligible? 53

54. Summary-I (from Workshop N-N*) P 33 (1232), P 11 (1440), D 13 (1520), & S 11 (1535). Transition form factors for P 33 (1232), P 11 (1440), D 13 (1520), & S 11 (1535). measured over large Q 2 range.  no sign of approaching asymptotic QCD limit --> need for 12 GeV upgrade  pion dressing of vertex needed to describe form factors. Roper P 11 (1440) transition form factor determined for the first time.  zero-crossing of magnetic form factor  behaves like a Q 3 radial excitation at short distances  Q 2 <0.7 GeV 2 determined from the 1π and 2π exclusive channels, as well as from a combined analysis of both these channels, are in a good agreement (also in agreement with MAID – Tiator) Able to extract reliable results on N* electrocouplings from meson electroproduction data. P 11 (1440) and D 13 (1520)  the P 11 (1440) and D 13 (1520). 1π and 2π channels have completely different nonresonant mechanisms AND ARE IN AGREEMENT!  description of all observables in both these channels with common N* electrocouplings good testing ground for efficacy of 2π: JM06, 1π: JLab/GWU- SAID/MAID reaction models. 54

55. Summary II (from Workshop N-N*) Exists good prospect to relate QCD and Q 2 evolution of N*s within the framework of Dyson-Schwinger & Bethe-Salpeter approaches and Lattice QCD (with caveat of more powerful computers) as determined through Light Cone wavefunctions. Healthy progress in Constituent Quark Models Can extract reliable information on N* electrocouplings from combined fit of multiple polarization observables in Nπ, Nππ, pη, and KY in electro- and photoproduction needed to resolve ambiguities in baryon resonance analysis. EBAC essential to support the baryon resonance program with coupled channel calculations 55