Vibrational States in theϒSpectroscopy

Abstract

Vibrational states, which are expected (in the string picture) in addition to ordinary $Q\overline{Q}$ bound states, are investigated in the $\Upsilon$ spectroscopy by use of a phenomenalogical approach. The lowest $1^{--}$ vibrational state is predicted to be below the continuum threshold, between the radial excitations ${\Upsilon }^{\prime \prime }$ and ${\Upsilon }^{\prime \prime \prime }$. Its mass is estimated to be 990 (±90) MeV above $\Upsilon$ with a leptonic width of 0.20 (±0.15) keV.