Pion interferometry analysis for 1.2 GeV/nucleon Ar on KCl

The technique of pion interferometry is used to study the pion source for central collisions of 1.2 GeV/nucleon Ar on KCl. The data are described by a Gaussian source of radius 3.8 +- 0.5 fm, a lifetime of 5.4 +- 1.8 fm/c and a degree of coherence of 0.74 +- 0.17. The sensitivity of the analysis to the two-particle phase space is discussed. A comparison with previously reported results at 1.5 GeV/nucleon is presented.