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HK: Fachverband Physik der Hadronen und Kerne

HK 36: Focus Session II: Emergence of Collectivity in Few-Body Hadron Systems

HK 36.1: Invited Talk

Wednesday, March 13, 2024, 14:00–14:30, HBR 14: HS 1

Observing the emergence of elliptic flow — •Sandra Brandstetter, Philipp Lunt, Carl Heintze, Maciej Galka, Keerthan Subramanian, Marvin Holten, Philipp Preiss, and Selim Jochim — Physikalisches Institut, Universität Heidelberg

Elliptic flow, the redistribution of energy between axes during the expansion due to anisotropic pressure gradients, is considered a signature of hydrodynamics. It has been observed in systems ranging from ultracold quantum gases (1) to heavy ion collisions (2), where surprisingly small systems show elliptic flow. Our cold atom experiment opens up a new pathway to study elliptic flow in few body systems with an unprecedented control over its microscopic parameters.

We start by deterministically preparing a small number of ultracold fermionic Li6 in the ground state of an elliptically-shaped optical trap and study the dynamics of the system after release from the trap at different interaction strengths and particle numbers (3). Owing to our experimental ability to measure both momentum- and real- space density with single particle resolution we observe the redistribution of momenta as well as the inversion of the aspect ratio over time. Additionally, we observe a formation of pairs as the system expands. In the near future, this will allow us to study the connection between the formation of pairs, entanglement and the emergence of collectivity in few body systems.

(1)K. M. OHara et al. Science 298.5601 (2002)

(2)Braun-Munzinger, P., Stachel, J. Nature 448, 302-309 (2007)

(3)S. Brandstetter, P. Lunt et al. arXiv: 2308.09699v1 (2023)

Keywords: Fermions; Ultracold; Hydrodynamics; Elliptic Flow; Few-body