- th / 9 90 60 19 v 1 8 J un 1 99 9 MKPH - T - 99 - 4 Medium Effects in Coherent Pion Photo - and Electroproduction on 4 He and 12

ar X iv : n uc l - th / 9 90 10 54 v 1 1 9 Ja n 19 99 KVI

The chiral two-pion exchange component of the long-range pp interaction is studied in an energy-dependent partial-wave analysis. We demonstrate its presence and importance, and determine the chiral parameters c i (i = 1, 3, 4). The values agree well with those obtained from pion-nucleon amplitudes.

Medium Eeects in Coherent Pion Photo-and Electroproduction on 4 He and 12 C Typeset Using Revt E X

Coherent 0 photo-and electroproduction on 4 He and 12 C nuclei is investigated in the framework of a distorted wave impulse approximation in momentum space. The elementary process is described by the recently developed unitary isobar model. Medium eeects are considered by introducing a phe-nomenological self-energy. The recent experimental data for 4 He and 12 C can be well described over a wid...

l - th / 9 90 20 25 v 1 1 0 Fe b 19 99 1 Pre - critical Chiral Fluctuations in Nuclear Medium — precursors

It is shown that an enhancement in the spectral function near 2m π threshold in the I=J=0 channel is a good signal of the partial restoration of chiral symmetry in nuclear medium. Several experiments are discussed to detect the enhancement, which uses hadron-nucleus and photo-nucleus reactions.

ar X iv : n uc l - th / 9 90 10 97 v 2 3 0 Ja n 19 99 1 The Landau - Migdal Parameters , g ′ NN and g ′ N ∆ and Pion

l - th / 9 80 30 09 v 2 2 7 M ay 1 99 8 Coherent Photoproduction of Pions on Spin - Zero Nuclei in a relativistic , non - local Model ∗ †

A relativistic and non-local model for the coherent photoproduction of pions on spin-zero nuclei is presented. The production operator is derived from an effective Lagrangian model that contains all the degrees of freedom known to contribute to the elementary process. Using the framework of DWIA, the matrix elements of this operator are evaluated using relativistic bound state wave functions. F...