Search for an eta bound state in pion double charge exchange on 18O.

Abstract

The search for an \ensuremath{\eta} bound state in the double charge exchange (DCX) reaction $^{18}\mathrm{O}$(${\mathrm{\ensuremath{\pi}}}^{+}$,${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$${)}^{18}$Ne(DIAS) has been carried out at LAMPF using the ${\mathit{P}}^{3}$ channel and the LAS spectrometer. An excitation function for this reaction was measured for energies ranging from 350 to 440 MeV and for momentum transfers of 0, 105, and 210 MeV/c. The measured cross sections tend to agree with previous results for DCX on $^{18}\mathrm{O}$. The measured excitation function shows some evidence for structure near the \ensuremath{\eta} production threshold.