A standard convention for particle-level Monte Carlo event-variation weights

TL;DR

This paper proposes a standardized, extensible naming convention for particle-level Monte Carlo event-variation weights, improving systematic uncertainty representation and interoperability across tools in particle physics analyses.

Contribution

It introduces a community standard for labeling and interpreting event-variation weight streams in Monte Carlo generators, facilitating consistent analysis.

Findings

Standardized naming improves compatibility across tools

Enables more accurate systematic uncertainty analysis

Supports both theoretical and experimental studies

Abstract

Streams of event weights in particle-level Monte Carlo event generators are a convenient and immensely CPU-efficient approach to express systematic uncertainties in phenomenology calculations, providing systematic variations on the nominal prediction within a single event sample. But the lack of a common standard for labelling these variation streams across different tools has proven to be a major limitation for event-processing tools and analysers alike. Here we propose a well-defined, extensible community standard for the naming, ordering, and interpretation of weight streams that will serve as the basis for semantically correct parsing and combination of such variations in both theoretical and experimental studies.