Beyond Scale Variations: Perturbative Uncertainties from Theory Nuisance Parameters

by Frank Tackmann

Monday 3 Feb 2025, 14:15 → 15:30 Europe/Berlin

I will discuss a new approach to estimate the theory uncertainty due to
missing higher orders in perturbative predictions. In this approach the true
underlying sources of the theory uncertainty are parameterized in terms of
theory nuisance parameters (TNPs), which has many advantages compared to
traditional methods based on scale variations: It provides correct theory
correlations and allows for consistent error propagation and combination.
Furthermore, the TNPs can be profiled in fits, allowing the data to reduce the
theory uncertainties. It also allows maximally exploiting all available,
even partial, higher-order information to reduce the theory uncertainty.
I will explain why these advantages are becoming mandatory for precision
analyses. As a concrete application, I will discuss the case of
the resummed transverse momentum spectrum in Drell-Yan production,
where the TNP approach has enabled the precise W-boson mass measurement
by CMS and will allow for a precise determination of the strong coupling
constant from the Z pT spectrum.