Small systems and the single-hit approximation in the AMY parton cascade Alpaca

• DOI: 10.1016/j.physletb.2024.138952
• Publication Date: 2024-08-08T17:29:19Z
• Authors: Robin Törnkvist; Korinna Zapp
• Keywords: Kinetic Theory; Momentum (technical analysis)

Understanding how momentum anisotropies arise in small collision systems is important for a quantitative understanding of collectivity terms QCD dynamics and large systems. In this letter we present results from the newly developed parton cascade Alpaca, which faithfully encodes AMY effective kinetic theory. Alpaca reproduces quantitatively previously known calculation single-hit approximation values coupling. We discuss detail such comparison to be carried out. Particularly at larger coupling generic difference between two approaches becomes apparent, namely that cascades particles interact over finite distance while direct integrations Boltzmann equation interactions are local. This leads differences extracted elliptic flow coefficient. These discrepancies appear situations where mean free path not compared interaction time applicability theory thus questionable.