Observation of Missing Energy Associated withμ+μ−Produced inp-Fe Interactions

Abstract

In a study of interactions of 400-GeV protons in an iron calorimeter, we have observed ${\mu }^{+}{\mu }^{-}$ pairs associated with a significant amount of missing energy indicative of final-state neutrinos. This missing energy is not due to any instrumental effects, nor to any trivial sources like double $K\overline{K}$ (or $\pi \pi$) decay. Interpretation of these data as production of a $D\overline{D}$ pair followed by a double muonic decay leads to a model-dependent estimate of a total production cross section of the order of 7-20 μb.