Number 56 (Story #4), November 15, 1991 by Phillip F. Schewe and Ben Stein A HEAVY VERSION OF THE W BOSON , if it exists, must have a mass greater than 520 GeV/c2. Some versions of the Standard Model of particle interactions permit the possibility of such a particle, without specifying what its mass would be. (The W is one of the carriers of the weak nuclear force.) The Collider Detector at Fermilab (CDF) collaboration sought the W', as it is called, at energies up to 1.8 TeV, but found none, and can only specify a lower limit on its mass. (F. Abe et al., Physical Review Letters, 4 November 1991.)