Jun 13 – 17, 2011
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Proceedings are now available online at <a href="http://www.slac.stanford.edu/econf/C110613/">eConf</a>

Nucleon resonance electrocouplings from CLAS data on pion electroproduction

Jun 16, 2011, 2:55 PM
Club 1 (Künstlerhaus)

Club 1


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Dr Victor Mokeev (Jefferson Lab)


Studies of nucleon resonance electrocouplings for excited proton states at various photon virtualities Q2 represent an important part in the N* Program with the CLAS detector [1]. The CLAS measurements extend the data on differential cross sections for N\pi and N\eta electroproduction channels, longitudinally polarized beam/beam-target asymmetries for \pi electroproduction off protons considerably, providing a nearly complete coverage of the final hadron phase space. Electrocouplings of the P11(1440), D13(1520), and S11(1535) resonances were determined from analyses within the framework of two conceptually different reaction models [2] at Q2 from 0.3 to 5.0 GeV2, and at Q2 from 0.3 to 6.0 GeV2 for the P33(1232) state. Data were also collected on charged double pion electroproduction off protons leading to nine independent differential \pi+\pi-p cross sections [3]. Using a phenomenological approach [4] allowed us to establish all essential mechanisms contributing to this channel at invariant masses of final hadrons W less then 1.8 GeV, and Q2 up to 1.5 GeV2. The P11(1440) and D13(1520) electrocouplings were determined from the \pi+\pi-p electroproduction data for the first time. They are in a good agreement with the results of the independent N\pi electroproduction analyses [2], offering evidence for the reliable extraction of resonance electrocouplings. First results from the \pi+\pi-p electroproduction channel on electrocouplings of S11(1650), D33(1700), and P13(1720) resonances have also become available. Analyses of these results in quark models and evaluation of the N* meson-baryon dressing [5] strongly suggests two contributions to \gamma{v}NN* electrocouplings: a) an internal quark core, and b) an external meson-baryon cloud. A further extension of the N* Program with the CLAS12 detector after completion of JLAB 12 GeV Upgrade Project will be outlined. References. 1. I.G.Aznauryan, et al., arXiv:1102.0597 (2011). 2. I.G.Aznauryan, et al., Phys. Rev. C80, 055203 (2009). 3. G.V.Fedotov, et al., Phys. Rev. C80, 015204 (2009). 4. V.I.Mokeev, et al., Phys. Rev. C80, 045212 (2009). 5. B.Julia-Diaz, et al., Phys. Rev. C77, 045205 (2008).

Primary author

Dr Victor Mokeev (Jefferson Lab)


Dr Inna Aznauryan (Erevan Physics Institute) Dr Volker Burkert (Jefferson Lab)

Presentation materials