[Clas_hadron] Contrinuted talk for the Fall DNP Meeting

[Viktor Mokeev]

Dear Colleagues,

 Please find below the draft of my contributed talk for Mini-Symposium 14e-"Advances in the exploration of the excited nucleon spectrum and structure" at the Fall DNP Meeting. I appreciate your comments. The deadline for submission is July 1st.

 Best Regards,
                            Victor



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                           Recent results in the studies of the high-lying nucleon resonances
                           from the CLAS data on \pi^+\pi^-p electroproduction.

                                    V.D.Burkert, R.W.Gothe and V.I.Mokeev for the CLAS Collaboration.

                                Jefferson Lab, University of South Carolina, and Moscow State University.


  The exclusive double-pion electroproduction represents the primary source of information on the structure of excited proton states in the mass region M_{N^*}>1.6 GeV. Most of these resonances decay preferentially to the final states with two pions. The recent preliminary results on electrocouplings and \pi \Delta and \rho p hadronic decays of almost all prominent excited proton states in the mass range from 1.6 to 1.8 GeV will be presented. They were obtained from analysis of the CLAS data on \pi^+\pi^-p electroproduction at photon virtualities 0.5<Q^2<1.5 GeV^2 [1] within the framework of the reaction model [2] updated based on the analysis of the \pi^+\pi^-p electroproduction cross sections at invariant masses of the final hadron system up to 1.8 GeV.  Our results confirmed the electrocouplings of F15(1680) resonance determined in the studies of N\pi exclusive channels [3], which have particular sensitivity to this state.  Instead, the S31(1620), D33(1700), and  P13(1720) resonances have dominant decays to the N\pi\pi final states. Electrocouplings of these resonances were determined for the first time from analysis of \pi^+\pi^-p electroproduction with a good accuracy. The results on electrpocouplings of most excited proton states in the mass range up to 1.8 GeV available from CLAS provide stringent constraints for the development of QCD-based
approaches aimed at describing the complex structure of excited nucleon
states and the dynamics of non-perturbative strong interaction which is responsible for the resonance formation.

References
1. M.Ripani et al., CLAS Collaboration, Phys. Rev. Lett. 91, 022002 (2003).
2. V.I.Mokeev et al., Phys. Rev. C80, 045212 (2009).
3. L.Tiator et al., Eur. Phys. J. ST198, 141 (2011).



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-- 
Prof. Ralf W. Gothe
Department of Physics and Astronomy
University of South Carolina
Columbia, SC 29208

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