Collective flow in high-multiplicity proton-proton collisions

Understand

We present an evidence of strong radial flow in high-multiplicity pp collisions.

• We analyze the CMS data on the inclusive spectra of the charged pions, kaons and protons in the LHC $\sqrt{s}=7$ TeV collisions.
• For $<N_{\mathrm{tracks}} >\gtrsim 75$ we demonstrate the consistency of the hydrodynamic description with the (idealized) Gubser's flow.
• Using a one parameter fit of the model to experimental data, we obtain the initial fireball size to be of the order of 1 fm.