Systematic Regge theory analysis of omega photoproduction

Systematic analysis of available data for $\omega$-meson photoproduction is given in frame of Regge theory. At photon energies above 20 GeV the $\gamma{+}p{\to}\omega{+}p$ reaction is entirely dominated by Pomeron exchange. However, it was found that Pomeron exchange model can not reproduce the $\gamma{+}p{\to}\rho{+}p$ and $\gamma{+}p{\to}\omega{+}p$ data at high energies simultaneously with the same set of parameters. The comparison between $\rho$ and $\omega$ data indicates a large room for meson exchange contribution to $\omega$-meson photoproduction at low energies. It was found that at low energies the dominant contribution comes from $\pi$ and $f_2$-meson exchanges. There is smooth transition between the meson exchange model at low energies and Regge theory at high energies.Comment: 7 pages, 8 figures, revtex

Relativistic Heavy--Ion Collisions in the Dynamical String--Parton Model

We develop and extend the dynamical string parton model. This model, which is based on the salient features of QCD, uses classical Nambu-Got\=o strings with the endpoints identified as partons, an invariant string breaking model of the hadronization process, and interactions described as quark-quark interactions. In this work, the original model is extended to include a phenomenological quantization of the mass of the strings, an analytical technique for treating the incident nucleons as a distribution of string configurations determined by the experimentally measured structure function, the inclusion of the gluonic content of the nucleon through the introduction of purely gluonic strings, and the use of a hard parton-parton interaction taken from perturbative QCD combined with a phenomenological soft interaction. The limited number of parameters in the model are adjusted to $e^+e^-$ and $p$--$p$ data. Utilizing these parameters, the first calculations of the model for $p$--$A$ and $A$--$A$ collisions are presented and found to be in reasonable agreement with a broad set of data.Comment: 26 pages of text with 23 Postscript figures placed in tex

Measurement of the charged multiplicity of events containing bottom hadrons at Ec.m.=91 GeV.

Using an impact-parameter tag to select an enriched sample of Z0bb» events, we have measured the difference between the average charged multiplicity of bb» and all hadronic Z0 decays to be 2.11.8(stat) 0.6(syst) tracks per event. The resulting total (nonleading) charged multiplicity for Z0 bb» events is 23.1(12.0)1.8 0.6 tracks. A comparison of this nonleading multiplicity to hadronic multiplicity data in the range of 10 to 60 GeV supports the hypothesis of flavor-independent hadronic fragmentation, and yields a measurement of the average energy fraction of bottom hadrons in Z0 decays of xEb=0.620.100.04. © 1992 The American Physical Society