Correlations at Small Relative Momenta among Protons Produced in Collisions of 1.8-GeV/nucleonAr40with a KC1 Target

Correlations between two protons produced in the inclusive reaction $\mathrm{Ar}+\mathrm{KCl}\to p+p+X$ at 1.8 GeV/nucleon have been measured for proton rapidities near the beam rapidity $Y_B$ and near $\frac{Y_B}{2}$. Comparison with model calculations suggests that the size of the region of final scattering is 3.5 fm at $Y_B$ and corresponds to that expected for a projectile remnant. The sizes we obtain at $\frac{Y_B}{2}$ (with or without high multiplicity requirements) are smaller (2.4-2.8 fm) and seem inconsistent with a thermalized source containing a large fraction of the available nucleons.