Study of event activities in high-multiplicity proton + proton collisions using Pythia8

Abstract

Heavy-ion collisions provide a unique opportunity for the laboratory tests for understanding the evolution of our Universe. The nuclear matter experiences several stages of evolution, starting from the production of partons to the nal state particles like hadrons. In order to collect the evidences about these stages of matter we need to examine some of the signals predicted in the evolution of the early universe. Heavy quarks and their bound states like J= plays an important role in describing the properties of matter at high energy density since they are produced at the early stages of collisions. This thesis comprises the study from the quark level to the formation of hadrons. In this work we have shown the production of charm quarks and its correlation with the production of heavy avour (J= ) and open heavy avour (D meson) particles in high multiplicity p+p collision using the pQCD inspired model PYTHIA8. In order to have the information about screening e ect due the presence of medium, we have done a study regarding the suppression of yields in case of high multiplicity p+p collisions. We have explained another important method called two particle azimuthal correlation, to explain the properties of the strongly interacting nuclear matter produced in ultra-relativistic heavy ion collisions. In this current work we have presented the measurements of two particle azimuthal correlation with neutral pion ( 0), neutral kaon (k0) and proton as trigger particles having the highest transverse momentum (pT ) and associated charged hadrons having transverse momentum (pT ) > 0.5 GeV/c in an event. This has been done on the basis of the difference in azimuthal angle ( ) and pseudorapidity ( ) at midrapidity in p+p collisions at p s = 13 TeV using a widely accepted theoretical model - PYTHIA8. Measurements based on the multiplicity dependent study can also explain the particle production as well as hadronization mechanisms at different multiplicities. We have used the two particle angular correlation function in order to extract the flow coefficients, which explains the collectivity of the matter formed and the effect of multi-partonic interactions in case of collectivity is briefly discussed.