We show how pion-nucleus scattering data can be used to constrain four-quark in-medium matrix elements, whose uncertainty is currently the most important problem inhibiting the use of QCD sum rules to study hadrons in nuclear matter, a problem related to early-universe phase transitions. We take an important step towards determining the matrix elements by extracting a value for a particular linear combination using the Isobar-Doorway model propagator of the in-medium Δ(1232) and a QCD sum rule analysis of both the free and in-medium Δ.

• Received 7 February 1995

DOI:https://doi.org/10.1103/PhysRevC.52.1022