## Abstract

We present the general properties of jets produced by e^{+}e^{-} annihilation. Their production and fragmentation characteristics have been studied with charged particles for c.m. energies between 12 and 43 GeV. In this energy range e^{+}e^{-} annihilation into hadrons is dominated by pair production of the five quarks u, d, s, c and b. In addition, hard gluon bremsstrahlung effects which are invisible at low energies become prominent at the high energies. The observed multiplicity distributions deviate from a Poisson distribution. The multiplicity distributions for the overall event as well as for each event hemisphere satisfy KNO scaling to within ∼20%. The distributions of x_{p}=2 p/W are presented; scale breaking is observed at the level of 25%. The quantity x_{p}dδ/dx_{p} is compared with multigluon emission calculations which predict a Gaussian distribution in terms of ln(1/x). The observed energy dependence of the maximum of the distributions is in qualitative agreement with the calculations. Particle production is analysed with respect to the jet axis and longitudinal and transverse momentum spectra are presented. The angular distribution of the jet axis strongly supports the idea of predominant spin 1/2 quark pair production. The particle distributions with respect to the event plane show clearly the growing importance of planar events with increasing c.m. energies. They also exclude the presence of heavy quark production, e^{+}e^{-}→Q {Mathematical expression} for quark masses up to 5QQ|=2/3) and 7QQ|=1/3). The comparison of 1/σ_{tot}dδ/dp_{T} measured at 14, 22 and 34 GeV suggests that hard gluon bremsstrahlung contributes mainly to transverse momenta larger than 0.5 GeV/c. The rapidity distribution for W≧22 GeV shows an enhancement away from y=0 which corresponds to an increase in yield of 10-15% compared to the centre region (y=0). The enhancement probably results from heavy quark production and gluon bremsstrahlung. The particle flux around the jet axis shows with increasing c.m. energy a rapidly growing number of particles collimated around the jet axis, while at large angles to the jet axis almost no W dependence is observed. For fixed longitudinal momentum p_{{norm of matrix}} approximate "fan invariance" is seen: The shape of the angular distribution around the jet axis is almost independent of W. The collimation depends strongly on p_{{norm of matrix}}. For small p_{{norm of matrix}}, p_{{norm of matrix}}{norm of matrix} the particles tend to be emitted closer and closer to the jet axis.

Original language | English (US) |
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Pages (from-to) | 307-340 |

Number of pages | 34 |

Journal | Zeitschrift für Physik C Particles and Fields |

Volume | 22 |

Issue number | 4 |

DOIs | |

State | Published - Dec 1984 |

## All Science Journal Classification (ASJC) codes

- Physics and Astronomy (miscellaneous)