The negative-pion multiplicity is measured for central collisions of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ with KCl at eight energies from 0.36 to 1.8 GeV/nucleon and for ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ on KCl and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ on Ba${\mathrm{I}}_2$ at 977 and 772 MeV/nucleon, respectively. A systematic discrepancy with a cascade-model calculation which fits proton- and pion-nucleus cross sections but omits potential-energy effects is used to derive the energy going into bulk compression of the system. A value of the incompressibility constant of $K=240\mathrm{}$ MeV is extracted in a parabolic form of the nuclear-matter equation of state.

• Received 2 July 1982

DOI:https://doi.org/10.1103/PhysRevLett.49.1236