2001/04/30 by M. Köhl, M. Kohl, M. Kuss +41 · 1 citation
Physics and Astronomy · #Nuclear physics research studies #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #nucl-ex
paper · pdf · doi:10.1016/s0370-2693(02)01345-x
published as Phys.Lett.B530:67-73,2002 · Elsart, 12 pages and 4 figures, Correspondent: Professor Dr. Dr. h.c. mult. Achim Richter, [email protected], submitted to Phys. Rev. Lett
arxiv created 2002/01/30 · openalex publication_date 2002/03/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
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+ 1.7- 2.1) MeV/c2 in the neutron-rich nuclear medium at a density of ρ= (0.057+ 0.085- 0.057) fm-3. Our data are consistent with the Δ self energy determined from measurements of π0 photoproduction from 4He and heavier nuclei.