Efficiently simulating quarkonium's evolution beyond the dipole approximation

¹ INFN - Sezione di Torino, via Pietro Giuria 1, Torino, Italy
² Institut de Ciències del Cosmos, Universitat de Barcelona, Martí i Franquès 1, Barcelona, Catalonia
³ Dipartimento di Fisica, Università di Torino and INFN Torino, Via Pietro Giuria 1, Torino, Italy

^* e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Published online: 17 April 2026

Abstract

The open quantum system framework allows one to compute quarkonium's evolution in a medium, keeping track of the needed quantum features. However, computing this evolution is a computationally demanding task. QTRAJ is an efficient code that allows one to simulate the behavior of quarkonium in a medium in the case in which the medium sees quarkonium as a small color dipole rT ≪ 1. While this limit is accurate for ϒ(1S), its applicability to other quarkonium states is unclear. In this talk, we present a generalization of this code that incorporates the regime where rT ~ 1 in the one-gluon exchange approximation. In its new version, QTRAJ implements new jump operators connecting different states, which are then expanded in plane waves, giving rise to a variation of the algorithm present in QTRAJ 1.0 where jumps with Δℓ> 1 are allowed. We will show a review of this approach comparing the rT ≪ 1 and rT ~ 1 cases, and we present preliminary phenomenological results.