Comment on quark searchers

We argue that due to a small difference in the current masses of u- and d-quarks, white quarks with screened colour could be bound electromagnetically only to a medium size nucleus, but not to the iron nucleus, studied in the experiments of Marinelli and Morpurgo. We indicate also that existing beam-dump experiments can be used to reach higher sensitivity in order to search for quarks in hadronic collisions. (orig.)