Is Upsilon(10580) really Upsilon(4S)?

Abstract

We analyse electron-positron data for b-bbar production published by the BABAR Collaboration, in the invariant-mass interval delimited by the B-Bbar and Lambda(b)-Lambda(b) thresholds. In particular, we describe the Upsilon(10580) enhancement, not as a b-bbar resonance, but rather as a threshold phenomenon due to the opening of the B-Bbar decay channel and enhanced by the Upsilon(2D) bound-state pole not far below this threshold. The same data provide evidence for the true Upsilon(4S) resonance, which we find at 10.735 GeV with a width of 38 MeV. At higher energies, two more known Upsilon resonances are observed by us in the data and classified. The vital role played in our analysis by the universal confinement frequency omega is again confirmed, via a comparison with the charmonium spectrum.