Measurement of the Recoil Polarization in thep(e→,e′p→)π0Reaction at theΔ(1232)Resonance

Autor: I. Ewald, Justin I. McIntyre, R. D. Ransome, Glen A. Warren, U. Müller, H. Schmieden, Th. Walcher, J.M. Friedrich, Michael Seimetz, Ingo Sick, D. Baumann, Harald Merkel, G. Rosner, Daniela Rohe, F. Klein, P. Bartsch, A. Wagner, J. Lac, Klemen Bohinc, S. Hedicke, M. O. Distler, M. Kahrau, P. Merle, R. Böhm, S. S. Kamalov, S. Širca, M. Ding, M. Weis, D. Elsner, A. Süle, R. Geiges, J. Bermuth, M. Potokar, L. Tiator, S. Derber, P. Jennewein, K. W. Krygier, Th. Pospischil, R. Neuhausen, A. Liesenfeld, Dieter Drechsel
Rok vydání: 2001
Předmět:
Zdroj: Physical Review Letters. 86:2959-2962
ISSN: 1079-7114
0031-9007
DOI: 10.1103/physrevlett.86.2959
Popis: The recoil proton polarization has been measured in the $p(\stackrel{\ensuremath{\rightarrow}}{e}{,e}^{\ensuremath{'}}\stackrel{\ensuremath{\rightarrow}}{p}){\ensuremath{\pi}}^{0}$ reaction in parallel kinematics around $W\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1232\phantom{\rule{0ex}{0ex}}\mathrm{MeV}$, ${Q}^{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.121\phantom{\rule{0ex}{0ex}}(\mathrm{GeV}/c{)}^{2}$, and $\ensuremath{\epsilon}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.718$ using the polarized cw electron beam of the Mainz Microtron. All three proton polarization components, ${P}_{x}/{P}_{e}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(\ensuremath{-}11.4\ifmmode\pm\else\textpm\fi{}1.3\ifmmode\pm\else\textpm\fi{}1.4)%$, ${P}_{y}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(\ensuremath{-}43.1\ifmmode\pm\else\textpm\fi{}1.3\ifmmode\pm\else\textpm\fi{}2.2)%$, and ${P}_{z}/{P}_{e}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(56.2\ifmmode\pm\else\textpm\fi{}1.5\ifmmode\pm\else\textpm\fi{}2.6)%$, could be measured simultaneously. The Coulomb quadrupole to magnetic dipole ratio, $\mathrm{CMR}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(\ensuremath{-}6.4\ifmmode\pm\else\textpm\fi{}{0.7}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.8}_{\mathrm{syst}})%$, was determined from ${P}_{x}$ in the framework of the Mainz Unitary Isobar Model. The consistency among the reduced polarizations and the extraction of the ratio of longitudinal-to-transverse response is discussed.
Databáze: OpenAIRE
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