Dimuon enhancement at 28 GeV and tentative (pseudo)scalar partner of the Z boson at 57.5 GeV.

The CMS Collaboration at the LHC recently reported an accumulation of data around 28 GeV in the invariant-mass distribution of muon pairs in association with a b quark jet and at least a second jet. This is analysed here in the light of the possible existence of a (pseudo)scalar boson with mass of about 57.5 GeV. We find that part of the data may originate in the radiative decay of Z bosons into pairs consisting of the lighter boson and a photon, giving rise to dimuon decay products that either stem from the photon or from the (pseudo)scalar boson.