# Exposing the QCD Splitting Function with CMS Open Data

## TL;DR

This paper demonstrates how to measure the QCD splitting function directly using jet substructure data from CMS Open Data, providing new insights into fundamental QCD properties at the LHC.

## Contribution

First measurement of the QCD splitting function using CMS Open Data through jet substructure analysis, establishing a novel method for probing fundamental QCD properties.

## Key findings

- Successful extraction of the QCD splitting function from CMS Open Data
- Validation of jet substructure observable as a probe for QCD properties
- First physics analysis based on publicly released CMS data

## Abstract

The splitting function is a universal property of quantum chromodynamics (QCD) which describes how energy is shared between partons. Despite its ubiquitous appearance in many QCD calculations, the splitting function cannot be measured directly since it always appears multiplied by a collinear singularity factor. Recently, however, a new jet substructure observable was introduced which asymptotes to the splitting function for sufficiently high jet energies. This provides a way to expose the splitting function through jet substructure measurements at the Large Hadron Collider. In this letter, we use public data released by the CMS experiment to study the 2-prong substructure of jets and test the 1 -> 2 splitting function of QCD. To our knowledge, this is the first ever physics analysis based on the CMS Open Data.