Self energies of the pion and the Δ isobar from the 3He(e, e′π+)3H reaction

M. Kohl, P. Bartsch, D. Baumann, J. Bermuth, R. Böhm, K. Bohinc, S. Derber, M. Ding, M. O. Distler, I. Ewald, J. Friedrich, J. M. Friedrich, P. Jennewein, M. Kahrau, S. S. Kamalov, A. Kozlov, K. W. Krygier, M. Kuss, A. Liesenfeld, H. MerkelP. Merle, U. Müller, R. Neuhausen, Th Pospischil, M. Potokar, C. Rangacharyulu, A. Richter, D. Rohe, G. Rosner, H. Schmieden, G. Schrieder, M. Seimetz, S. Širca, T. Suda, L. Tiator, M. Urban, A. Wagner, Th Walcher, J. Wambach, M. Weis, A. Wirzba

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9 Citations (Scopus)


In a kinematically complete experiment at the Mainz microtron MAMI, pion angular distributions of the 3He(e,e′π+)3H reaction have been measured in the excitation region of the Δ resonance to determine the longitudinal (L), transverse (T), and the LT interference part of the differential cross section. The data are described only after introducing self-energy modifications of the pion and Δ-isobar propagators. Using Chiral Perturbation Theory (ChPT) to extrapolate the pion self energy as inferred from the measurement on the mass shell, we deduce a reduction of the π+ mass of Δmπ+ = (-1.7-2.1+1.7) MeV/c2 in the neutron-rich nuclear medium at a density of p = (0.057-0.057+0.085) fm-3. Our data are consistent with the Δ self energy determined from measurements of π0 photoproduction from 4He and heavier nuclei.

Original languageEnglish
Pages (from-to)67-73
Number of pages7
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Issue number1-4
Publication statusPublished - 2002 Mar 28
Externally publishedYes


  • Delta resonance region
  • Few-body system
  • He
  • Longitudinal-transverse separation
  • Medium effects
  • Pion electroproduction
  • Self energy

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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