Recursive Soft Drop

TL;DR

Recursive Soft Drop is a novel jet grooming technique that applies multiple Soft Drop layers to improve mass resolution of boosted objects, maintaining effectiveness under high pileup conditions.

Contribution

It introduces Recursive Soft Drop, a generalization of Soft Drop with multiple layers, enhancing jet mass resolution and pileup robustness, including a global event-wide grooming variant.

Findings

Improves jet mass resolution for boosted objects.

Maintains performance under high pileup conditions.

Provides a global grooming approach for entire events.

Abstract

We introduce a new jet substructure technique called Recursive Soft Drop, which generalizes the Soft Drop algorithm to have multiple grooming layers. Like the original Soft Drop method, this new recursive variant traverses a jet clustering tree to remove soft wide-angle contamination. By enforcing the Soft Drop condition N times, Recursive Soft Drop improves the jet mass resolution for boosted hadronic objects like W bosons, top quarks, and Higgs bosons. We further show that this improvement in mass resolution persists when including the effects of pileup, up to large pileup multiplicities. In the limit that N goes to infinity, the resulting groomed jets formally have zero catchment area. As an alternative approach, we present a bottom-up version of Recursive Soft Drop which, in its local form, is similar to Recursive Soft Drop and which, in its global form, can be used to perform event-wide grooming.