EPJ

2021 Impact factor 3.131
EPJ A - Hadrons and Nuclei
Hadrons and Nuclei
Eur. Phys. J. A 1, 427-433

Proton polarization in the $\bf p(\mathaccent''017E e,e'\mathaccent''017E p\,)\pi^0$ reaction and the measurement of quadrupole components in the N to $\bf \Delta$ transition

H. Schmieden

Institut für Kernphysik der Johannes Gutenberg-Universität, 55099 Mainz, Germany

Received: 3 November 1997 Communicated by B. Povh

Abstract
The recoil proton polarization in the $\pi^0$ production off the proton with longitudinally polarized electron beam has been studied as a means to measure quadrupole components in the N to $\Delta$ transition. On top of the $\Delta$ resonance a high sensitivity to a possible Coulomb quadrupole excitation is found in parallel kinematics. The ratio of S1+/M1+ multipole amplitudes can be determined from the ratio of the two in-scattering-plane recoil proton polarization components. Avoiding the absolute measurement of the polarizations, such a ratio allows small experimental uncertainties. Furthermore, the electron helicity independent proton polarization component enables the characterization of resonant and non-resonant pieces.

PACS
14.20.Gk Baryon resonances with S=0 - 13.60.Rj Baryon productions - 13.60.Le Meson production - 13.40.-f Electromagnetic processes and properties - 13.60.-r Photon and charged-lepton interactions with hadrons

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