1. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 1 Nucleon Resonance Studies with CLAS12 D. Arndt, H. Avakian, I. Aznauryan, A. Biselli, W.J. Briscoe, V. Burkert, V.V. Chesnokov, P.L. Cole, D.S. Dale, C. Djalali, L. Elouadrhiri, G.V. Fedotov, T.A. Forest, E.N. Golovach, R.W. Gothe*, Y. Ilieva, B.S. Ishkhanov, E.L. Isupov, K. Joo, T.-S.H. Lee, V. Mokeev*, M. Paris, K. Park, N.V. Shvedunov, G. Stancari, M. Stancari, S. Stepanyan, P. Stoler, I. Strakovsky, S. Strauch, D. Tedeschi, M. Ungaro, R. Workman, and the CLAS Collaboration Theory Support Group V.M. Braun, I. Cloët, R. Edwards, M.M. Giannini, B. Julia-Diaz, H. Kamano, T.-S.H. Lee, A. Lenz, H.W. Lin, A. Matsuyama, M.V. Polyakov, C.D. Roberts, E. Santopinto, T. Sato, G. Schierholz, N. Suzuki, Q. Zhao, and B.-S. Zou JLab PAC 34, January 26-30, 2009  Motivation: N* electrocoupling & mechanisms of baryon formation  Methods of the data analysis: DM,UIM,JM CLAS models  Experiment feasibility: Resolution, Acceptance and Beam Time Estimates  Conclusion

2. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 2 Physics Goals  Determine electro-couplings of prominent excited nucleon states (N *, Δ * ) in the range Q 2 = 5 - 12 GeV 2.  Experimental tools are differential cross sections and polarization observables in single and double pseudo-scalar meson production:  + n  0 p,  p and  +   p measured in full polar and azimuthal angle ranges. These data for the first time will allow us to:  Study the structure of excited nucleon states in domains where dressed quarks are major active degrees of freedom  Explore the formation of excited nucleon states in interactions of dressed quarks and their emergence from QCD

3. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 Progress in Experiment and Phenomenology 3 Dressed quarks (I. Aznauryan; M.Giannini, et al ; B.Julia-Diaz, et al.) Meson-baryon cloud (EBAC) Nππ Nπ Nππ Nπ pπ 0 Δ(1232)P 33 N(1440)P 11 N(1520)D 13 Recent experimental and phenomenological efforts show that meson- baryon contributions to resonance formation drop with Q 2 faster than contributions from dressed quarks.

4. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 Resonance electrocouplings from Lattice QCD 4 Comparison of N* electro-couplings at high Q 2 with LQCD projections will test to what degree the strong interactions of dressed quarks is responsible for the formation of excited nucleon states.  LQCD calculations of the Δ(1232) and N(1440) transitions have been carried out with large π-mass. By the time of the Upgrade LQCD calculations of N* electro-couplings will be extended to Q 2 = 10 GeV 2 near the physical  -mass as part of the commitment of the JLAB LQCD and EBAC groups in support of this proposal. Δ(1232)P 33 N(1440)P 11

5. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 LQCD & Light Cone Sum Rule (LCSR) Approach 5 LQCD is used to determine moments of N* distribution amplitudes (DA). N* electro-couplings are determined from respective DA’s within the LCSR framework. N(1535)S 11 Calculations of N(1535)S 11 electro-couplings at Q 2 up to 12 GeV 2 are already available and shown by shadowed bands on the plot. By the time of Upgrade electro-couplings of others N*’s will be evaluated. These studies are part of the commitment of the U. Regensburg group in support of this proposal. CLAS Hall C

6. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 Dyson-Schwinger Equation (DSE) Approach 6 DSE provides a way of relating N* electro-couplings at high Q 2 to QCD and to test theory capability to describe N* formation based on QCD. DSE approaches provide the link between dressed quark propagators, form factors, scattering amplitudes and QCD N* electro-couplings can be determined by applying Bethe-Salpeter /Fadeev equations to 3 dressed quarks with properties and interactions derived from QCD By the time of Upgrade DSE electro-couplings of several excited nucleon states will be available as part of the commitment of Argonne NL, the U. of Washington, and EBAC.

7. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 The dynamical mass of light dressed quarks 7 LQCD and DSE predict generation of dynamical momentum dependent mass of dressed quark, that comes from gluon dressing of current quark propagator. Dynamical contributions account for ~97% of light dressed quark mass, while < 3 % come from Higgs mechanism. Data on N* electro-coupling at 5.<Q 2 <12 GeV 2 will allow us to chart the momentum evolution of dressed quark mass, in particular, to explore a rapid transition from dressed to almost bare current quark shown in the plot. per dressed quark Q 2 ~ (1. [GeV]*3[number of quarks]) 2 ~9 GeV 2

8. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 Cont’d 8 N* electro-couplings should be sensitive to the momentum dependence of the dressed quark mass. This affects the dressed quark propagator qq-correlations. Detailed studies of manifestation of dressed quark mass momentum dependence in Q 2 -evolution of N* electro-couplings will be carried out by Argonne NL/U. of Washington groups by 2014 NJL calculations of elastic form factors with two different values of non- running dressed quark mass shown in plots demonstrate the sensitivity to the dressed quark mass. m q =0.360 GeV m q =0.425 GeV

9. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 Constituent Quark Models (CQM) 9 Relativistic CQM are the currently only available tool for studies of electro-couplings for the majority of excited proton states. The approximate agreement between LC-CQM calculations of N* electro-couplings and data suggests that CQM can be used in initial phenomenological analysis of resonance electro-couplings at high Q 2 in order to: determine relevant degrees of freedom: major 3 quark and possible admixture of multi-quark components, and sea quarks determine symmetries of binding interactions and their evolution at small distance scales that will be achieved for the first time constrain N* light cone wave functions This activity represent part of the commitment of the University & INFN of Genova, and the Beijing IHEP groups.

10. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 10 PDG value Active degrees of freedom in N(1440)P 11 structure vs Q 2 Pion Cloud (EBAC) |q 3 +qq  (Li, Riska) 3q NπNπ, Nππ combined analysis Different LC CQM calculations give similar results Meson-Baryon contributions drop rapidly with Q 2.

11. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 Impact of proposed experiment on hadron physics 11 Data on N* electro-couplings at high Q 2 will extend considerably information on nucleon structure in terms of dressed quarks. Non-perturbative interactions of dressed quarks are responsible for formation of both ground and excited nucleon states. In order to fully explore these mechanisms and their emergence from QCD, combined analysis of the data on structure of ground and excited nucleon states is required. CLAS12 is the only facility that will be capable of investigating N* structure at high Q 2. Proposed experiment is only available in 12 GeV Research Program, that addresses the studies of excited nucleon states, providing crucial piece of information on non- perturbative strong interactions responsible for nucleon and baryon formation from fundamental constituents: quarks and gluons.

12. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 Transverse Charge Densities of the N ➞ Roper The charge distribution of the Roper + shows a dense core and a large ‘halo’. Pion cloud ? M. Vanderhaeghen, L. Tiator 12

13. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 13 Nucleon Resonances in N  /Nπ  Electroproduction p(e,e’)X p(e,e’p)   p(e,e’  + )n p(e,e’p  + )  -   channel is sensitive to N*’s heavier than 1.4 GeV  Provides information that is complementary to the N  channel  Many higher-lying N*’s decay preferably to N  final states Q 2 < 4.0 GeV 2 W in GeV

14. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 Tools for Phenomenlogical Analysis Unitary Isobar Model (UIM) approach in single p.s. meson production Fixed-t Dispersion Relations (DR) Isobar Model for Nππ final state (IM) Coupled channel approach (EBAC) 14

15. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 Unitary Isobar Model (UIM) for N  Analysis  N re-scattering in the final state are taken into account in the K- matrix approximation I. Aznauryan, Phys. Rev. C67, 015209 (2003) + + ++ + + n n ++ Non-res. amplitudes: gauge inv. Born terms; pole/regge-ized meson t-channel exchange+ s- u- nucleon terms          15

16. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 Dispersion relations for 6 invariant Ball amplitudes: 17 UnsubtractedDispersion Relations 1 Subtracted Dispersion Relation γ*p→Nπ (i=1,2,4,5,6) Fixed-t Dispersion Relations for invariant Ball amplitudes 16

17. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 17 Legendre Moments of Unpolarized Structure Functions Q 2 =2.05GeV 2 Two conceptually different approaches DR and UIM are consistent. The CLAS data offer sufficient constraints to check validity of the models K. Park et al. (CLAS), Phys. Rev. C77:015208, 2008 I. Aznauryan DR fit w/o P11 I. Aznauryan DR fit I. Aznauryan UIM fit

18. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 18 Legendre Moments of Full Set of Structure Functions Analysis approaches utilize model-independent PW decomposition in Legendre polynomials, while resonant contributions were isolated within the framework of the models tested against most extensive worldwide data sets on various observables in N  electro-production unpolarized LT, TT LT’ Q 2 =2.44 GeV 2 DR UIM

19. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 19 JM model for analysis of p  +  - electroproduction

20. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 Mechanisms of JM model determined from the CLAS 2  data 20 Any contributing mechanism has considerably different shapes of cross sections in various observables, defined by particular behavior of their amplitudes. Successful description of all observables allowed us to check or to establish dynamics of all essential contributing mechanisms Full JM calc  -   ++  + D 13 (1520)  + F 15 (1685) pp 2  direct

21. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 Separation of resonant/non-resonant contributions in 2  cross sections 21 Considerable resonant contributions and substantial differences in the shapes of resonant/non-resonant parts of cross sections in all observables make it possible to isolate the resonant contributions and to determine the N* parameters. resonant part non-resonant part

22. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 Electrocouplings of N(1440)P 11 from CLAS data 22 Nπ (UIM, DR) PDG estimation , Nπ  combined analysis Nπ  -electroproduction (JM)

23. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 23 Electrocouplings of D13(1520) state from the CLAS 1  /2  data world data before CLAS experiments Consistent values of N* electro-couplings determined from analyses of 2 major electro- production channels with fundamentally different non-resonant mechanisms. Allows us to establish model uncertainties for the extracted electro-couplings.

24. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 24 Electrocouplings of high lying N*’s from CLAS 2  data. D33(1700) P13(1720) First consistent mapping of Q 2 - dependence for D33(1700), P13(1720) electrocouplings Analysis of 1  /2  electroproduction channels open up an opportunity to determine electrocouplings for majority of excited proton states

25. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 25 Kinematic Coverage of CLAS12 Genova-EG SI-DIS (e ’,  + ) detected (e ’, p) detected (e ’,  + ) detected (E,Q 2 )(5.75 GeV, 3 GeV 2 )(11 GeV, 3 GeV 2 )(11 GeV, 12 GeV 2 ) N+N+ 1.41  10 5 6.26  10 6 5.18  10 4 NpNp - 4.65  10 5 1.45  10 4 NpNp - 1.72  10 4 1.77  10 4 60 days L=10 35 cm -2 sec -1, W=1535 GeV,  W= 0.100 GeV,  Q 2 = 0.5 GeV 2

26. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 26 Angular Acceptance of the CLAS12 Acceptance  Acceptance for cos  = 0.01

27. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 27 W (GeV) W Resolution with CLAS12 1.5 < W < 2 GeV 2 < W < 2.5 GeV2.5 < W < 3 GeV W as calculated from electron scattering: 26 MeV 18 MeV 13 MeV

28. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 28 W Resolution with CLAS12 2 < W < 2.5 GeV2.5 < W < 3 GeV W as calculated from exclusive p  +   final state: 7.5 MeV 10 MeV W (GeV) 1.5 < W < 2 GeV 4.5 MeV

29. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 29 Missing Mass Resolution and Final State Selection ep  e’p’  + X W < 2 GeV ep  e’p’  +  - X EXEX 2  : black curve 3  : red curve In 20% of all events 4 particles are reconstructed 22 33 33 22

30. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 30 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

31. Ralf W. Gothe NSTAR12 Proposal JLab PAC 34 31 Conclusion 60 days at E = 11 GeV,  W = 0.025 GeV,  Q 2 = 0.5 GeV 2, and L= 10 35 cm -2 sec -1 provide data for  1  and 2  independent analyses in the unexplored 5<Q 2 <12 GeV 2 region  Combined 1  and 2  analysis  Full coupled channel analysis developing by EBAC at Jlab.  First results on N* electrocouplings at the distance scales corresponding to major contribution from dressed quarks needed for broad international collaboration between experimentalists and theorists in order to explore non- perturbative strong interactions of dressed quarks responsible for baryon formation and their emergence from QCD  Shed light on origin of major part of hadronic mass in Universe