Possible lepton universality breaking in Upsilon decays: a light CP-odd Higgs interpretation and consequences

A light CP-odd Higgs boson mixing with ηb hadronic resonances can show up by inducing a slight but observable lepton universality breaking in Upsilon decays. Besides, hyperfine splittings mϒ(nS)−mηb(nS) might also be sensitive to the mixing providing another hint of the existence of such a light pseudoscalar Higgs. On the other hand, recent findings from astroparticle and cosmology favouring a light dark matter constituent (with mass about 10 GeV or less) cast a new interest into the search for invisible decays of ϒ resonances performed at B factories.