ANOMALOUS MASS-NUMBER DEPENDENCE OF NUCLEAR TRANSPARENCY

We examine the target mass number (A) dependence of the nuclear transp arency calculated for (e, e' p) reactions. Generally, the transparency is proportional to A(-1/3) for large A's and has weaker A-dependence as A decreases. The conventional nuclear physics calculation yields a transparency whose A(-1/3) dependence is reached in rather light nucle i (around A = 20). If either the proton mean-free path in nuclei becom es substantially longer, or the internal structure of the proton is ex plicitly incorporated in the calculation, however, the A(-1/3) depende nce is reached only in extremely heavy nuclei. The A-dependence should thus serve as a signature of the so-called color-transparency phenome non.