The Monte Carlo program KORALZ version 4.0 for lepton or quark pair production at LEP/SLC energies

Abstract

A Monte Carlo program for τ pair production and decay applicable to the experiments in e +e − colliders in the Z resonance energy range is presented. The program includes initial and final state bremsstrahlung corrections up to the O (α 2) (with exclusive exponentiation), and O (α) electroweak corrections. More than twenty distinct τ decay modes can be generated: (a) leptonic modes τ −→ v̄ve −(γ) and v̄vμ -(γ); (b) one-meson modes, vπ − and vK −; (c) two-me son modes, ν{π − π 0} ρ − , ν{K − π 0} K ∗− and ν{K 0π −} K ∗− ; (d) three-meson modes, ν {π − 2π 0} a − 1 , ν{2π − π +} a − 1 , νK + K − π −, νK̄ 0K 0π −, νK −K̄ 0π 0, νK −π 0π 0, νK −π −π +, νK 0π 0π - and νηπ −π 0; (e) four-pion modes, νπ −3π 0, and ν2π −π +π 0 (including the ωπ − contribution); (f) multi-pion modes, ν nπ ±,0 with n>4; and finally the decay τ -→νπ -π 0γ from the ω→πγ. Complete O (α) QED corrections are included in the leptonic decay channels, and for other decay channels an interface is provided to the PHOTOS Monte Carlo generator for approximate simulation of the QED corrections. The program includes three libraries of pure electroweak corrections from three independent groups of authors. The program can also be used for the generation of final states different from τ +τ - pairs, i.e., it is able to generate μ +μ -, νḡn, and under some restrictions uū, dd̄, cc̄, ss̄ and bb̄ final states.