Study of sequential semileptonic decays of b hadrons produced at the   Tevatron
  We present a study of rates and kinematical properties of lepton pairs contained in central jets with transverse energy E_T > 15 GeV that are produced at the Fermilab Tevatron collider. We compare the data to a QCD prediction based on the HERWIG and QQ Monte Carlo generator programs.We find that the data are poorly described by the simulation, in which sequential semileptonic decays of single b quarks (b --> l c X with c --> l s X) are the major source of such lepton pairs. 
G. Apollinari, M. Barone, I. Fiori, P. Giromini, F. Happacher, S.   Miscetti, A. Parri and F. Ptohos