Observation of resonances in the reaction ${\rm \bar p p} \rightarrow \pi^0\eta\eta$ at 1.94 GeV/ $c^2$

Abstract

Antiproton–proton annihilation into \(\pi^0\eta\eta\) has been studied with the Crystal Barrel spectrometer at CERN at an incident beam momentum of 1.94 GeV/c. The data were taken with a trigger requiring neutral final states. A new isovector state, the \(a_2(1660)\) decaying to \(\pi^0\eta\), is observed. In the \(\eta\eta\) invariant mass region around 2.1 GeV/\(c^2\), strong production of a heavy resonance is required, but our analysis does not distinguish between \(J^P = 0^+\), \(2^+\) and \(4^+\). The production of the \(f_0(1500)\) in reactions in flight is also observed.