Global Fits to Electroweak Data Using GAPP

TL;DR

Global Fits to Electroweak Data Using GAPP introduces a dedicated FORTRAN framework for performing high-precision global electroweak analyses within the $\overline{\rm MS}$ scheme. The tool computes pseudo-observables from a broad set of data (e.g., Z pole measurements, low-energy tests) and fits SM parameters such as $M_Z$, $M_H$, $m_t$, $\alpha_s$, and $\hat{m}_c$, while allowing new-physics parameters like oblique $S,T,U$ and anomalous $Z$ couplings. It incorporates state-of-the-art radiative corrections, including full one-loop EW, enhanced two-loop, mixed EW/QCD, and four-loop QED running for $\hat{\alpha}$, and handles mass schemes to avoid renormalon ambiguities by using $\overline{\rm MS}$ masses for quarks. The package also covers $Z$-widths and asymmetries, low-energy observables, neutrino scattering, and the $b\to s\gamma$ transition (NLO RG-evolved Wilson coefficients), enabling consistent global constraints on the SM and potential new physics. Overall, GAPP provides a flexible, up-to-date platform for extracting fundamental parameters, assessing theory uncertainties, and forecasting the impact of ultrahigh-precision measurements such as $M_W$ on the electroweak fit.

Abstract

At Run II of the Tevatron it will be possible to measure the W boson mass with a relative precision of about 2 times 10^-4, which will eventually represent the best measured observable beyond the input parameters of the SM. Proper interpretation of such an ultrahigh precision measurement, either within the SM or beyond, requires the meticulous implementation and control of higher order radiative corrections. The FORTRAN package GAPP, described here, is specifically designed to meet this need and to ensure the highest possible degrees of accuracy, reliability, adaptability, and efficiency.