QM 2022

Angular Momentum in Heavy-Ion Collisions via the Hadronic Transport Approach SMASH

6 Apr 2022, 17:34

4m

Poster Chirality, vorticity and spin polarization Poster Session 1 T02

Speaker

Nils Sass

Description

We investigate the angular momentum in heavy-ion collisions applying the hadronic transport approach SMASH. In contrast to geometrical models (e.g. a Glauber approach) our transport approach allows to access the full phase-space information of every particle at any time. The importance of understanding the non-equilibrium angular momentum transferred to the fireball and in turn the quark-gluon plasma (QGP) was highlighted by recent results of the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The spin polarization measurement of the $\mathrm{\Lambda }$-hyperon revealed a high angular momentum of the heavy ions and provided experimental evidence for vorticity in the QGP for the first time. Therefore, a systematic exploration of the angular momentum within a dynamic calculation for beam energies from ${\sqrt{s}}_{NN}=2.41GeV$ to ${\sqrt{s}}_{NN}=200GeV$ is a crucial step towards the full description of vorticity as a fundamental property of the QGP. Results for the angular momentum of Au-Au collisions as function of the impact parameter are presented and the influence of the initial Fermi momentum is studied. Moreover, it is shown that the angular momentum exhibits a distinct maximum for a specific impact parameter, independent of the beam energy. We show that the remaining angular momentum $L_r$ of the system grows with increasing system size in a range of $A=16$ ${(}_8^{16}O)$ to $A=208$ ${(}_{82}^{208}Pb)$ while we observe that for smaller beam energies a larger fraction of the initial angular momentum is transferred to $L_r$. The findings are important to guide future experimental programs and indicate where the largest transfer of angular momentum is expected.

Presentation materials

Sass_QM22_AngularMomentum.pdf