Theory seminar (11am): Giulia Marinelli: From scales to shapes: theory uncertainties with theory nuisance parameters in the Drell-Yan qT spectrum

Thursday 17 Apr 2025, 11:00 → 12:00 Europe/Amsterdam

Veltman Centre (Nikhef)

The transverse momentum $q_T$ spectrum in the Drell–Yan production is a key observable for precision physics at the LHC. Recent measurements have reached sub-percent accuracy, opening the door to detailed studies of theoretical inputs that are crucial within the Standard Model. Given this level of precision — and the fact that an accurate description of the $q_T$ spectrum involves many different theoretical ingredients — a robust treatment of theoretical predictions and their associated uncertainties is essential. Among these, perturbative uncertainties remain dominant and are traditionally estimated via scale variations. However, this method has well-known limitations.

In this talk, I will present a novel approach based on theory nuisance parameters (TNPs) to quantify such uncertainties. This method properly accounts for theoretical correlations and enables the data itself to constrain, and potentially reduce, these uncertainties in a consistent way. To illustrate the potential of this framework, I will discuss an ongoing project involving the extraction of ${\alpha }_s(m_Z)$ and its uncertainty using fits to pseudodata, analyzing both perturbative and non-perturbative uncertainties. Although this study does not yet include other subdominant sources of theoretical uncertainty, which will be addressed in future extractions of ${\alpha }_{s}s(m_Z)$ from real experimental data,

I will briefly comment on the recent CMS $m_W$ determination, which successfully employed TNPs as part of its uncertainty modeling.