Production of muon pairs inKL0−Cuinteractions

The dimuon production mass spectrum has been measured with a beam of 4-20-GeV/c $K_L^0\text{'}\mathrm{s}$ incident on a copper target. The production of ${\mu }^{+}{\mu }^{-}$ pairs resulting from the decay of vector mesons ($\rho , \omega \mathrm{and} \phi$) was observed with a cross section of 55 ± 10 nb per nucleon for $x_F>0.25\mathrm{}$ based on a specific production model. In addition we measured upper limits for ${\mu }^{+}{\mu }^{-}$ pair production cross sections with $x_F>0.25\mathrm{}$ of 20 nb per nucleon for $m_{\mu \mu }<0.5\mathrm{}$ GeV/${\mathit{c}}^2$ and 35 nb per nucleon at the $\psi \mathrm{}\left(3100\right)\mathrm{}$.