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Theory uncertainties and missing higher orders at LHC
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Europe/Rome
Aula Conversi (Dip. di Fisica - Edificio G. Marconi)
Aula Conversi
Dip. di Fisica - Edificio G. Marconi
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Description
The topic of this afternoon is the quantification of theory uncertainty due to the missing higher orders in perturbative predictions. The canonical approach, based on the variation of unphysical scales, suffers from several limitations and may lead to unreliable estimates of these uncertainties, particularly in their correlations. Moreover, it lacks a clear probabilistic foundation.
The talks will present new approaches aimed at overcoming the limitations of scale variation. After a general introduction to probabilistic methods in high-energy physics and to the comparison between data and theory, alternative and powerful techniques to quantify theoretical uncertainties based on a Bayesian framework will be discussed.
A novel approach based on theory nuisance parameters (TNPs) will then be introduced. This method consistently accounts for theoretical correlations and enables the data itself to constrain, and potentially reduce, these uncertainties. To illustrate the potential of this framework, an ongoing project on the extraction of $\alpha_s(m_Z)$ and its uncertainty from the Z $q_T$ spectrum through fits to pseudodata will be presented. In addition, the recent CMS $m_W$ determination, which successfully employed TNPs as part of its uncertainty modelling, will be briefly discussed.
Finally, a modified version of the TNP approach that benefits from the Bayesian methods previously discussed will be introduced.