Fixed-Order Corrections in Sector Showers

by Christian Preuss (ETH Zürich)

Wednesday 22 Mar 2023, 14:00 → 15:00 Europe/Helsinki

FYS2 (JYFL)

While parton-shower algorithms provide reliable and versatile tools to describe collider observables in regions of phase space where radiation occurs at low energies or angles, they are insufficient to describe hard, well-separated jets. In order to achieve an accurate description over all of phase space, parton showers are therefore typically “matched” or “merged” with fixed-order calculations. These matching and merging strategies often build upon the construction of so-called “shower histories“, accounting for all possible branching sequences to arrive at a given multi-particle configuration. Constructing these histories at high particle multiplicities mandates fairly complex and resource-intensive algorithms. This issue can be mitigated by so-called sector showers, which divide the branching phase space into distinct “sectors”, each of which receives contributions from a single branching history only. 

I will give a comprehensive review of parton showers and matching and merging techniques and introduce the concept of sector showers as implemented in the Vincia antenna shower in Pythia 8.3. I will discuss how their bijective nature not only allows to improve the efficiency of merging algorithms but also facilitates the matching of parton showers to higher-order perturbative calculations.

talk.pdf