Observation of Prompt Single Muons and Dimuons in Hadron-Nucleus Collisions at 200 GeV/c

Abstract

We trigger a large-acceptance spectrometer by single muons and observe any additional muons with good efficiency. The effect of $\pi$ and $K$ decays is subtracted to obtain the prompt muon signal in the kinematic region $0.1<x<\mathrm{}0.4\mathrm{}$ and $p_T<1.0\mathrm{}$ GeV/c. We find 0.7 ± 0.2 of all prompt $\mu \text{'}\mathrm{s}$ are produced in pairs; the $\frac{\mu }{\pi }$ ratio decreases with $x$ but increases with $p_T$, averaging 3 × ${10}^{-5\mathrm{}}$.