Evidence for narrow $\Delta^0(1232)$ states in the ${}^{12}C(e,e'p\pi^-){}^{11}C$ Reaction

P. Bartsch; D. Baumann - et al.

doi:doi:10.1007/s100500050220

EPJ

Evidence for narrow $\Delta^0(1232)$ states in the ${}^{12}C(e,e'p\pi^-){}^{11}C$ Reaction

P. Bartsch¹ - D. Baumann¹ - J. Bermuth² - K. Bohinc³ - R. Böhm¹ - D. Bosnar⁴ - N. Clawiter¹ - S. Derber¹ - M. Ding¹ - M.O. Distler¹ - A. Ebbes¹ - I. Ewald¹ - J. M. Friedrich¹ - J. Friedrich¹ - P. Jennewein¹ - M. Kahrau¹ - M. Kohl⁵ - A. Kozlov¹ - K.W. Krygier¹ - M. Kuss⁵ - A. Liesenfeld¹ - H. Merkel¹ - P. Merle¹ - U. Müller¹ - R. Neuhausen¹ - T. Pospischil¹ - M. Potokar³ - D. Rohe² - G. Rosner¹ - H. Schmieden¹ - S. Sirca³ - A. Wagner¹ - T. Walcher¹ - M. Weis¹ - S. Wolf¹

¹ Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, D-55099 Mainz, Germany
² Institut für Physik, Johannes Gutenberg-Universität Mainz, D-55099 Mainz, Germany
³ Institut "Jozef Stefan'', University of Ljubljana, SI-1001 Ljubljana, Slovenia
⁴ Department of Physics, University of Zagreb, HR-10000 Zagreb, Croatia
⁵ Institut für Kernphysik, Technische Universität Darmstadt, D-64289 Darmstadt, Germany

Received: 23 December 1998 Communicated by B. Povh

Abstract
The reaction ${}^{12}C(e,e'\Delta^0){}^{11}C\rightarrow {}^{12}C(e,e'p\pi^-){}^{11}C$ was investigated at the Mainz Microtron MAMI in a triple coincidence measurement using the three spectrometer setup of the A1 Collaboration. The good missing mass resolution of $\sigma_{\mathrm m} = 0.27\,MeV/c^2$ allowed to select the events belonging to the ground state of ¹¹C. Cutting on these events the excitation energy spectra of ${}^{12}C_{\Delta^0}$ show evidence for two peaks of about $4\,MeV$ width (FWHM) at $282\,MeV$ and $296\,MeV$ with a significance of about 4.5 standard deviations. The peaks are interpreted in a simple weak coupling model as bound $\Delta^0$ states in ${}^{12}C_{\Delta^0}$ .

PACS
24.30.Gd Nuclear physics: Resonance reactions - 25.30.Rw Electroproduction reactions - 14.20.Gk Baryon resonances with S=0 - 21.80.+a Hypernuclei

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Evidence for narrow states in the Reaction

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Evidence for narrow $\Delta^0(1232)$ states in the ${}^{12}C(e,e'p\pi^-){}^{11}C$ Reaction