We present the first full $(3+1)\mathrm{D}$ dynamical simulations of ultraperipheral $\mathrm{Pb}+\mathrm{Pb}$ collisions at the Large Hadron Collider. Extrapolating from $p+\mathrm{Pb}$ collisions, we explore whether a quasireal photon ${\gamma }^{*}$ interacting with the lead nucleus in an ultraperipheral collision can create a many-body system exhibiting fluid behavior. Assuming strong final-state interactions, we provide model results for charged hadron multiplicity, identified particle mean transverse momenta, and charged hadron anisotropic flow coefficients, and compare them with experimental data from the ALICE and ATLAS Collaborations. The elliptic flow hierarchy between $p+\mathrm{Pb}$ and ${\gamma }^{*}+\mathrm{Pb}$ collisions is dominated by the difference in longitudinal flow decorrelations and reproduces the experimental data well. We have demonstrated that our theoretical framework provides a quantitative tool to study particle production and collectivity for all system sizes, ranging from central heavy-ion collisions to small asymmetric collision systems at the Relativistic Heavy-Ion Collider and the Large Hadron Collider and even at the future Electron-Ion Collider.

• Received 24 March 2022
• Revised 27 September 2022
• Accepted 8 November 2022

DOI:https://doi.org/10.1103/PhysRevLett.129.252302