Adequacy of Effective Born for electroweak effects and TauSpinner algorithms for LEP, Tevatron, HL-LHC and FCC simulated samples

Abstract

Matching and comparing the measurements of the past and future experiments calls for consistency checks of calculations used for their interpretation. On the other hand, new calculation schemes of the field theory can be beneficial for precision, even if they may obscure comparisons with earlier results. Over the years concepts of Improved Born, Effective Born as well as of effective couplings, in particular of sin 2 θ e f f W mixing angle for electroweak interactions, evolved. In our discussion we use four DIZET electroweak library versions; that of today and of the last 30 years. They were used for phenomenology of practically all HEP accelerator experiments. Versions differ by incremental updates of certain types of corrections which became available with time. We rely on the codes published and archived with KKMC Monte Carlo program for e + e − → f f n(γ). All these versions became recently available for TauSpinner algorithm of simulated event reweighting as well. Such reweighting can be performed after events are generated and stored in the data files. To this end DIZET is first invoked, and its results are used. Documentation of TauSpinner upgrade, to version 2.1.0, and of its arrangement for semi-automated EW effects benchmark plots are provided. Some details of the tool which can be used to complete simulation sample with electroweak effects are given.Focus is however on the numerical results, on the different approximations introduced in Improved Born to obtain Effective Born, suited better to match with QCD corrections. The τ lepton polarization P τ , forward backward asymmetry A FB and parton level total cross section σ tot are used to monitor size of electroweak effects and effective sin 2 θ e f f W picture limitations for precision physics. Collected results enumerate: (i) feasibility of Effective Born approximation and sin 2 θ e f f W , (ii) differences between versions of electroweak libraries and (iii) parametric ambiguities due to e.g. m t or ∆α (5) h (s). These results can be considered as examples only, but allow to evaluate adequacy of Effective Born with respect of Improved Born (definitions are addressed too).