A search was made at the Brookhaven alternating gradient synchrotron for magnetic monopoles produced either in collisions of 30-BeV protons with light nuclei, or produced by $\gamma$ rays secondary to these protons in the Coulomb field of protons or of carbon nuclei. In runs using 5.7×${10}^{15}$ circulating protons, no monopolelike event was found. This implies an upper limit for production in proton-nucleon interactions of about 2×${10}^{-40\mathrm{}}$ ${\mathrm{cm}}^2$. Experimental limits are also derived for the photoproduction of pole pairs.

• Received 30 October 1962

DOI:https://doi.org/10.1103/PhysRev.129.2326