Searching for small droplets of hydrodynamic fluid in proton–proton collisions at the LHC Wenbin Zhao, You Zhou, Koichi Murase and Huichao Song Eur. Phys. J. C, 80 9 (2020) 846 Published online: 12 September 2020 DOI: 10.1140/epjc/s10052-020-8376-x