Dileptons from ηc in nucleus–nucleus collisions

Preliminary estimates suggest that excess dimuon production with invariant mass in the range 1.5–2.5 GeV in nucleus–nucleus collisions can be explained on the basis of ηc production. This appears to be consistent with all the peripheral and central collision data with various nuclei such as S–U at 200 GeV/nucleon except for the central collision data on Pb–Pb at 158 GeV/nucleon. Some explanations based on glueball production for Pb–Pb data are discussed.