Figure 1

(a) $d_{\mathrm 0}$ distributions of electrons from beauty and charm hadron decays as well as from decays of light hadrons and from photon conversions obtained from PYTHIA simulations in the electron $\pt$ range $1 < \pt < 6$ Gev/$c$. The distributions were normalized to the same integrated yield. (b) Ratios of the measured and the simulated $d_{\mathrm 0}$ distributions of conversion electrons in the ranges $1 < \pt < 2$ Gev/$c$ and $2 < \pt < 6$ Gev/$c$ (points shifted in $d_{\mathrm 0}$ by 10 $\mu$m for better visibility).