Search for prompt neutrinos and new penetrating particles from 28-GeV proton-nucleus collisions

This paper describes a search for weakly or semistrongly interacting particles produced in the collision of 4.9 x 1018 28-GeV protons with a thick copper and brass beam stop. 104 events have been observed; their characteristics are similar to those produced by neutrinos arising from proton interactions in a 15-cm-thick brass target. However, compared to the number expected, an excess of 48 events is found with uncertainties of +- 10 (statistical) and +- 12 (systematic). At most ten events (68% confidence level) are attributable to beam losses