On the absorption of antibaryons in nuclei

Antiproton ($\bar{p}$) and antilambda ($\bar{\Lambda}$) production has been measured for minimum bias in $p$ + A collisions and central A$_{1}$ +A$_{2}$ collisions at the CERN-SPS by the collaborations NA35/49 and NA44. The measurements are extrapolated from rapidity distributions to absolute minimum bias cross sections. It is shown that the $\bar{p}$ cross sections divided by A$_{1} \cdot$ A$_{ 2}$ follow an exponential trend as a function of a characteristic length obtained from a Glauber type absorption model, while the $\bar{\Lambda}$ cross sections divided by A$_{1} \cdot$ A$_{ 2}$ are constant. The exponential trend also holds for $\bar{p}$ production at the lower energies of the Brookhaven AGS. A discussion of the physics interpretation of the established trends in terms of an effective absorption cross section is presented.