October 14, 2025 (remote)

Dr. Shengli Huang (Stony Brook University)

Location:  Room 328, Birge Hall, UC Berkeley Campus MAP 

Time: 4:00pm Pacific Time

ZOOM for those who are unable to come in-person: LINK

Host: Zhenyu Ye

Title: Probing the Origin of Azimuthal Anisotropy in Small Systems with Symmetric and Asymmetric Collisions by STAR at RHIC

Abstract: The observation of azimuthal anisotropy in small collision systems challenges our understanding of quark–gluon plasma (QGP) formation and evolution. To investigate the origin of this anisotropy, we compare anisotropic harmonics as functions of multiplicity in O+O and d+Au collisions at sqrt(sNN) = 200 GeV, which feature distinctly different initial geometries. The elliptic flow coefficients (v_2{2} and v_2{4}), extracted from two- and four-particle correlations, show strong system dependence, whereas the triangular flow (v_3{2}) exhibits only weak sensitivity. These trends are well reproduced by 3D-Glauber+MUSIC hydrodynamic calculations and are consistent with geometric expectations: the ratio v_n{2}/epsilon_n{2} remains approximately system-independent once sub-nucleonic fluctuations are included. This supports the interpretation that the observed anisotropy originates from QGP-driven hydrodynamic expansion. Our results demonstrate that comparing small symmetric and asymmetric systems enables the engineering of droplet shapes with unprecedented geometric control, thereby providing enhanced sensitivity to QGP properties.