Studies of charged particle multiplicity inb quark events

Abstract

Using the distance from the average primary vertex to reconstructed secondary vertices in jets, samples of events withb purity varying from about 13% to 89% have been selected. The charged particle multiplicity in the hemispheres opposite those containing these jets has been studied as a function of theb purity of the events. Extrapolating to 0% and 100%b purity, values of the hemisphere charged particle multiplicity inZ ⁰→$b\bar b$ events and in non-$b\bar b$ events have been measured to be

$$\begin{gathered} \bar n_b = 11.71 \pm 0.03 \pm 0.18 \pm 0.21, \hfill \\ \bar n_{udsc} = 10.32 \pm 0.01 \pm 0.07 \pm 0.19. \hfill \\ \end{gathered}$$

The first error is statistical, the second systematic and the third is a common systematic error.

The difference in charged particle multiplicity betweenb quark events and light (u, d, s) quark events has been measured and found to be

$$\delta _{bl} = 3.02 \pm 0.05 \pm 0.79.$$

The result is compared to the predictions of MLLA QCD calculations.

By studying the impact parameter distributions of charged particles in the hemispheres opposite these jets, the charged particle decay multiplicity ofB hadrons fromZ ⁰ decay, including particles fromK ⁰ _s and Λ decay, has been measured to be

$$\bar n^B = 5.51 \pm 0.05 \pm 0.51.$$

From the mean momentum of these decay products and separately from the number of primary charged particles perb event, the averagex _E ofb flavoured hadrons has been measured to be

$$\left\langle {x_E } \right\rangle _b = 0.693 \pm 0.003 \pm 0.030.$$