Observation of Massive Muon Pairs in Hadron Collisions

Muon pairs in the mass range $1<{m}_{\ensuremath{\mu}\ensuremath{\mu}}<6.7 \frac{\mathrm{Gev}}{{c}^{2}}$ have been observed in collisions of high-energy protons with uranium nuclei. At an incident energy of 29 GeV, the cross section varies smoothly as $\frac{d\ensuremath{\sigma}}{d{m}_{\ensuremath{\mu}\ensuremath{\mu}}}\ensuremath{\approx}\frac{{10}^{\ensuremath{-}32}}{m_{\ensuremath{\mu}\ensuremath{\mu}}^{}{}_{}{}^{5}} {\mathrm{cm}}^{2} {(\frac{\mathrm{GeV}}{c})}^{\ensuremath{-}2}$ and exhibits no resonant structure. The total cross section increases by a factor of 5 as the proton energy rises from 22 to 29.5 GeV.