We have observed production of monochromatic low-energy photons in $e^{+}$$e^{\mathrm{-}}$ interactions between 10.6 and 11.2 GeV/$c^2$. We show that this signal is associated with the production of b-flavored meson pairs, and interpret it as due to the decay $B^{\mathrm{*}}$→B+γ. This is the first experimental evidence for the existence of vector bū or bd¯ bound states. We determine the mass difference of the vector and pseudo- scalar states, M($B^{\mathrm{*}}$)-M(B), to be 52±2±4 MeV.

• Received 7 January 1985

DOI:https://doi.org/10.1103/PhysRevLett.55.36