New Decay Descriptor Parsing for LHCb

Since LHCb physics measurements focus on specific particle decays, the ability to locate certain decays (whether simulated or reconstructed) within the data is vital. The existing decay-finding code is in a state of partial migration away from the old LoKi-based framework which is intended to be dropped from the LHCb software stack. A new implementation was required with several new features in order to work with simulation.

The primary goals of this project were to add an interface to HepMC particles as well as integrate the new decay finder in the new generic generator-level cut tool for Gauss-on-Gaussino. Additionally, the parser needed to be extended to support simulation-specific syntax whilst being ported from regex to an appropriate parsing library.

This report documents the motivation for the new decay descriptor parser and decay finding solution for the LHCb Collaboration and describes the newly created implementation.