Study of soft QCD phenomena and double parton interactions with ATLAS

Despite the success of perturbative QCD predictions in the high-energy regime, QCD itself remains mysterious at its nominal non-perturbative QCD scale. The LHC offers rich opportunities to probe the core of QCD related questions by studying minimum bias events, double parton interactions, small-x and diffractive processes, as well as correlations in hadronization processes. This talk summarizes recent results from ATLAS, based on Run-2 LHC data samples: the first ATLAS observation of double parton scattering in leptonic decays of WW events, the measurement of strange particle production in the framework of underlying event, and the first combined measurement of parameters of helical QCD string in proton-proton and heavy ion collisions.