A study of charm hadron production in$Z^0 \to c\bar c$ and$Z^0 \to b\bar b$ decays at LEPdecays at LEP

Abstract

Measurements of the production of the weakly decaying charmed hadrons: D⁰, D⁺, D ⁺ _s andΛ ⁺ _c in both$Z^0 \to c\bar c$ and$Z^0 \to b\bar b$ events are reported. By summing the partial contributions from each of these states we measure the partial width for Z⁰ decays into a$c\bar c$ pair as:

$$\frac{{\Gamma _{c\bar c} }}{{\Gamma _{had} }} = 0.167 \pm 0.011(stat) \pm 0.011(sys) \pm 0.005(br)$$

where the errors are statistical, systematic and due to the uncertainties in the charmed hadron branching ratios, respectively. The relative production rates for the formation of the charmed hadrons from primaryc quarks is found to be in good agreement with continuum e ⁺ e ⁻ data at √s≈10 GeV.

The measured rates of these four charmed hadrons inb hadron decays is found to account for

$$1.061 \pm 0.045(stat) \pm 0.060(sys) \pm 0.037(br)$$

c or$\bar c$ quarks perb hadron decay. Comparison of the relative rates of the different charmed hadron species withϒ(4S) data indicates higher rates for D ^Emphasis>+ _s andΛ ⁺ _c hadrons and lower rates of D⁰ and D⁺ mesons as expected due to the different mixture ofb hadrons.