Observation of double ø-meson production in 100 and 175 GeV π−-Be interactions

Abstract Inclusive oo production has been studied in π − -Be interactions for 100 and 175 GeV incident momentum. An upper limit of 72 nb has been set for σ(π − Be → η c (2980) + X ) s BR (η c → oo) at 175 GeV . At both momenta the number of oo events is larger than expected for uncorrelated o pairs. A narrow width enhancement is observed at M oo ≈2100 MeV with a 4 standard deviation significance.