C-parameter hadronisation in the symmetric 3-jet limit and impact on α
European Physical Journal C 81:2 (2021)
Abstract:© 2021, The Author(s). Hadronisation corrections are crucial in extractions of the strong coupling constant (αs) from event-shape distributions at lepton colliders. Although their dynamics cannot be understood rigorously using perturbative methods, their dominant effect on physical observables can be estimated in singular configurations sensitive to the emission of soft radiation. The differential distributions of some event-shape variables, notably the C parameter, feature two such singular points. We analytically compute the leading non-perturbative correction in the symmetric three-jet limit for the C parameter, and find that it differs by more than a factor of two from the known result in the two-jet limit. We estimate the impact of this result on strong coupling extractions, considering a range of functions to interpolate the hadronisation correction in the region between the 2 and 3-jet limits. Fitting data from ALEPH and JADE, we find that most interpolation choices increase the extracted αs, with effects of up to 4 % relative to standard fits. This brings a new perspective on the long-standing discrepancy between certain event-shape αs fits and the world average.
Calculating the primary Lund Jet Plane density
JOURNAL OF HIGH ENERGY PHYSICS (2020) ARTN 170
Parton showers beyond leading logarithmic accuracy
Physical Review Letters American Physical Society 125 (2020) 052002
Abstract:Parton showers are among the most widely used tools in collider physics. Despite their key importance, none so far have been able to demonstrate accuracy beyond a basic level known as leading logarithmic order, with ensuing limitations across a broad spectrum of physics applications. In this Letter, we propose criteria for showers to be considered next-to-leading logarithmic accurate. We then introduce new classes of shower, for final-state radiation, that satisfy the main elements of these criteria in the widely used large-NC limit. As a proof of concept, we demonstrate these showers’ agreement with all-order analytical next-to-leading logarithmic calculations for a range of observables, something never so far achieved for any parton shower.
Novel tools and observables for jet physics in heavy-ion collisions
JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS 47:6 (2020) ARTN 065102
FCC-hh: The Hadron Collider: Future Circular Collider Conceptual Design Report Volume 3
EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS 228:4 (2019) 755-1107