A collinear shower algorithm for NSL non-singlet fragmentation

Journal article

We formulate a collinear partonic shower algorithm that achieves next-to-single-logarithmic (NSL, αsnLn−1) accuracy for collinear-sensitive non-singlet fragmentation observables. This entails the development of an algorithm for nesting triple-collinear splitting functions. It also involves the inclusion of the one-loop double-collinear corrections, through a z-dependent NLO-accurate effective 1 → 2 branching probability, using a formula that can be applied more generally also to future full showers with 1 → 3 splitting kernels. The specific NLO branching probability is calculated in two ways, one based on slicing, the other using a subtraction approach based on recent analytical calculations. We close with demonstrations of the shower’s accuracy for non-singlet partonic fragmentation functions and the energy spectrum of small-R quark jets. This work represents an important conceptual step towards general NNLL accuracy in parton showers.

Authors: van Beekveld, M; Dasgupta, M; El-Menoufi, BK; Helliwell, J; Monni, PF

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Springer
• Journal: Journal of High Energy Physics
• Volume: 2025
• Issue: 3
• Article number: 209
• Publication date: 2025-03-28
• Acceptance date: 2025-01-28
• DOI: 10.1007/jhep03(2025)209
• EISSN: 1029-8479
• ISSN: 1126-6708
• Language: English
• Keywords: Jets and Jet Substructure; Parton Shower