01506732

j

01506732 Jadach, S. Ward, B.F.L. W\c{a}s, Z. The precision Monte Carlo event generator ${\cal{KK}}$ for two-fermion final states in $e^+ e^-$ collisions. Comput. Phys. Commun. 130, No.3, 260-325 (2000). 2000 Elsevier Science B.V. (North-Holland), Amsterdam EN coherent exclusive exponentiation electroweak corrections Yennie-Frautschi-Suura exponentiation parton shower model spin polarization effects

doi:10.1016/S0010-4655(00)00048-5

Summary: We present the Monte Carlo event generator ${\cal K}{\cal K}$ version 4.13 for precision predictions of the electroweak standard model for the process $e^+ e^-\to f\overline f+ n\gamma$, $f= \mu,\tau,d,u,s,c,b$, at centre-of-mass energies from $\tau$ lepton threshold to 1 TeV, that is for LEP, SLC, future linear colliders, $b$, $c$, $\tau$-factories, etc. Effects due to photon emission from initial beams and outgoing fermions are calculated in QED up to second-order, including all interference effects, within Coherent Exclusive Exponentiation (CEEX), which is based on Yennie-Frautschi-Suura exponentiation. Electroweak corrections are included in first order, with higher-order extensions, using the DIZET 6.21 library. Final-state quarks hadronize according to the parton shower model using JETSET. Beams can be polarized longitudinally and transversely. Decay of the $\tau$ leptons is simulated using the TAUOLA library, taking into account spin polarization effects as well. In particular the complete spin correlations density matrix of the initial-state beams and final state $\tau$'s is incorporated in an exact manner. Effects due to beamstrahlung are simulated in a realistic way. The main improvements with respect to KORALZ are: (a) inclusion of the initial-final state QED interference, (b) inclusion of the exact matrix element for two photons, and (c) inclusion of the transverse spin correlations in $\tau$ decays (as in KORALB).