More data on the new particles: theory uncertain

High‐energy experimentalists are starting to paint a more complete, although still sketchy, picture of the new particles at 3.1 and 3.7 GeV that were discovered by surprise last November (see PHYSICS TODAY, January, page 17). Results so far are consistent with the early expectations that both particles are vector particles. They have been photoproduced, and the high‐energy resonance has been seen to decay into the lower one. Finally, these two particles appear to stand alone, as searches for other narrow resonances have so far yielded nothing except a broad peak at 4.1 GeV. Such was the picture presented by experimentalists from several institutions at the Annual APS Meeting in Anaheim, California from 29 January to 1 February. While the new results fit into some of the proposed theoretical schemes better than into others, they do not mesh completely with any of them. In a possibly related development, a weakly interacting particle carrying a new quantum number has been suggested by recent neutrino experiments. (See box on page 24.)