Narrow Results

A new scheme for calculating masses and boost-invariant wave functions of heavy quarkonia is developed in a light-front Hamiltonian formulation of QCD. Only the simplest approximate version with one flavor of quarks and an ansatz for the mass gap for gluons is discussed. The resulting spectra look reasonably good in view of the crude approximations made in the simplest version.

Hadronic events at the Z pole have been investigated in search for Colour Reconnection effects and QCD coherence. Colour Reconnection effects are searched for in three-jet events and the data results are compared to the predictions of different Monte Carlo models. QCD colour coherence effects are tested through the multiplicity distributions of hadrons with restricted momenta, and the LEP1 e⁺e^- data is compared to HERA e⁺p data under the equivalence assumption of the e⁺e^- hemisphere with the current region of the Breit frame of reference.

It is shown that the conventional mesons and the lowest glueball state can be reasonably described within a simple relativistic quantum-field model of interacting quarks and gluons under the analytic confinement by using a path-integral approach. The ladder Bethe-Salpeter equation is solved for the meson and glueball (gg) spectra. A minimal set of parameters (the quark masses m_f, the coupling constant α_s and the confinement scale Λ) is used to fit the latest experimental data. In spite of the simplicity, the model provides a reasonable framework to estimate the decay constants f_π and f_K as well as the non-exotic meson and glueball masses in a wide range of energy up to 10 GeV.