Higher Moments of Underlying Event Distributions

We perform an Underlying Event analysis for real data sets from pp collisions at center of mass energy $ \sqrt{s}=5 $ and 13 TeV and pPb collisions at $ \sqrt{s}=7 $ TeV at the LHC, together with the Monte Carlo data sets generated with Pythia8 and EPOS in the same conditions. The analysis is focused on the transverse region which is more sensitive to the Underlying Event, and performed as a function of the leading track transverse - momentum $p_t$ in each event. In our work, not only the average underlying event activity but also its fluctuation, namely its root mean square (RMS), Skewness and Kurtosis, are analyzed. We find that the particle density, energy density and their fluctuation magnitude (RMS) are suppressed at leading $p_t\approx$ 5 GeV/c for all these cases, with EPOS having evident deviation of 10\%-25\%. The higher moments skewness and kurtosis decrease rapidly in low leading $p_t$ region, and follow an interesting Gaussian-like peak centered at leading $p_t\approx$ 15 GeV/c.