[SEMINARI]: Dr. Kamalov: Excitation on the nucleon resonances in pion photo- and electroproduction

[Arcadi Santamaria]

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                              S E M I N A R I

             [Image]   Departament de Física Teòrica    [Image]
                          Universitat de València
                       Institut de Física Corpuscular
                       Universitat de València - CSIC

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             Excitation on the nucleon resonances in pion photo- and
                                electroproduction

                            Dr. Sabit S. Kamalov

          (Laboratory of Theoretical Physics, JINR, Dubna, Russia)

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                              Seminari del IFIC
                Thursday 21 of September of 2000 at 11:30 AM
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                                    Resum

    Using recently developed Unitary Isobar and Dynamical models nucleon
  resonances in the first, second and third resonance regions are analysed.
  Within Dynamical Model we find that the bare $\Delta(1232)$ resonance is
 almost spherical and the electric E2 and Coulomb C2 quadrupole excitations
      are nearly saturated by pion cloud contribution. From the recent
    $p(e,e'p)\pi^0$ at $Q^2=$ 2.8 and 4.0 (GeV/c)$^2$ we demonstrate that
  contribution from the electric E2 excitations, starting from a small and
 negative value at real photon point, shows a clear tendency to cross zero,
  and change sign with increasing $Q^2$. This is a possible indication of a
                   slow approach toward the pQCD region.

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