Femtoscopy of rotating sources

In this talk, we present a novel approach to probing the vorticity of collective flow in heavy-ion collisions. We begin by performing coarse graining of the output from a transport model to reconstruct the collective flow profile and confirm the presence of both global and local vorticity. Our analysis demonstrates that the system's rotation influences the space-time structure of particle emission and, in particular, leaves measurable imprints in proton–pion femtoscopic correlations. We show that the displacement between proton and pion emission centers serves as a quantitative indicator of the system's rotational strength. This leads to the identification of a new femtoscopic signal of vorticity in heavy-ion collisions. We further discuss the implications of this finding for studies of the nuclear equation of state and Λ hyperon polarization, highlighting how this new observable can help resolve persistent challenges in the spin physics of relativistic fluids.