Dimuon production in 15.5-GeV/<i>c</i><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>π</mml:mi><mml:mi>p</mml:mi></mml:math>interactions and the observation of a low-mass continuum

Abstract

We report the results of an experiment which examines the entire final state of events in which muon pairs were produced in 15.5-GeV/c ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}p$ interactions. A portion of this data was presented earlier. Here we report on the final data sample of 890 events obtained from a total of 2.5\ifmmode\times\else\texttimes\fi{}${10}^{8}$ interactions [a sensitivity of (8.65 events/nb)\ifmmode\times\else\texttimes\fi{}trigger efficiency]. The experiment was sensitive primarily to the low-mass region and the good mass resolution made it possible to identify the contributions from the $\ensuremath{\rho}$ and $\ensuremath{\omega}$ decays and the $\ensuremath{\eta}$ and $\ensuremath{\omega}$ Dalitz decays. An excess of events is observed in the dimuon mass region \ensuremath{\sim}400 - 600 MeV which is not accounted for by the above-mentioned decays. The final states were examined to search for characteristic differences from those in events without dimuons.