On the precision of calculations of initial state radiation in the LEP Z line-shape fits

Calculation of initial state radiation (ISR) in the fitting program MIZA and in the Standard Model program BHM is improved within the analysis of the Z line-shape measurements at LEP. The uncertainty on the determination of the Z line-shape parameters coming from the precision of ISR calculations is 2×10−4 on σ0 and 0.1 MeV on mZ and ΓZ.