Identified Hadron Production as a Function of Event Multiplicity and Transverse Spherocity in pp Collisions at √s = 7 and 13 TeV with the ALICE Detector

Abstract: This study reports on identified hadron production as a function of event multiplicity (dNch/dη) and transverse spherocity (SO) in proton-proton collisions at √s = 7 and 13 TeV measured with the ALICE detector at the LHC. The particle spectra and their ratios measured in high-multiplicity events show signatures of an expanding medium. Integrated particle yields as a function of multiplicity measured in pp collisions at √s = 7 and 13 TeV are compared to those measured in p-Pb and Pb-Pb collisions. Hadrochemical composition of particles are found to be similar in different colliding systems under different √s, provided similar multiplicities are compared. This suggests that hadron yields are dominantly driven by dNch/dη , and not the colliding system or center-of-mass energy. On the other hand, particle spectra measured in pp collisions at √s = 13 TeV is harder than that at 7 TeV, when similar dNch/dη are compared. In addition, hadron production as a function of multiplicity is studied in the context of statistical, hydrodynamical and pQCD-inspired models. In order to disentangle the soft QCD component from the hard, high-multiplicity pp collisions at √s = 13 TeV are studied as a function of transverse spherocity. It is found that the amount of flow-like effects in the data sample can be controlled using event shape observables.