Model Independent Methods for Determining B(Y(5S)->Bs^{(*)}   anti-B}_s^{(*)})$
  We describe a method that provides a model independent measurement of the Bs fraction in Y(5S) resonance decays, fs, using the relative rates of like-sign versus opposite sign dileptons; the like-sign leptons result from B^0 and Bs mixing. In addition, we show that determining the rates of single, double and triple Ds mesons provides an alternative way of finding fs. 
Radia Sia and Sheldon Stone