Improving Parton Shower Physics in Herwig 7
The next era of particle physics is rapidly approaching. With the upcoming High-Luminosity LHC and proposals for a Future Circular Collider, experiments will deliver collision data with unprecedented precision. Our simulation tools must match that accuracy.
While significant progress has been made in fixed-order calculations, the event-generator and resummation communities are now pushing parton showers to higher logarithmic accuracy. As of 2025, several formalisms achieve Next-to-Leading-Log (NLL) accuracy — including:
- PanLocal and PanGlobal
https://gsalam.web.cern.ch/panscales/ - FHP (Forshaw–Holguin–Plätzer)
https://arxiv.org/abs/2003.06400 - Alaric
https://arxiv.org/abs/2404.14360 - Apollo
https://arxiv.org/abs/2403.19452
— with exploratory steps toward NNLL precision.
This project integrates the PanGlobal and FHP showers into Herwig, alongside its existing Catani–Seymour shower, enabling NLL-accurate predictions within mainstream collider simulations.
Preliminary results are shown below. More details will be added once our publication is released. In the meantime, please see my recent presentation:
📌 NLL Showers in Herwig – LHC Monte Carlo Working Group (Oct 2025)
