On the absorption of antibaryons in nuclei

Antiproton (p̄) and antilambda (Λ̄) production has been measured for minimum bias in p+A collisions and central A₁+A₂ 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 p̄ cross sections divided by A₁·A₂ follow an exponential trend as a function of a characteristic length obtained from a Glauber type absorption model, while the Λ̄ cross sections divided by A₁·A₂ are constant. The exponential trend also holds for p̄ 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.