Search for the Intermediate Vector Boson

A search for the vector boson ($W$ particle), postulated as the mediator of the weak interaction, has been carried out by determining the intensity and polarization of muons originating very near the point of interaction of 28-GeV protons with nucleons. Bosons were not observed and the upper limit on the production cross section for $W$'s with masses between 2.0 and 4.5 $\frac{\mathrm{GeV}}{c^2}$ is $B{\sigma }_W\lesssim 6\times {10}^{-36\mathrm{}}$ ${\mathrm{cm}}^2$, where $B$ is the branching ratio for the $W$ decay to a muon and a neutrino. A comparison between the measured flux of muon pairs and the flux expected on the basis of a plausible model for the production and decay of both $W$'s and heavy virtual $\gamma$'s suggests that the experiment may not have been sensitive to $W$'s, if they exist in this mass region. The flux of high-energy muons produced directly by an unknown process, an $X$ process, is determined to be no greater than ${10}^{-6\mathrm{}}$ times the pion flux.