His M.Sc. thesis was based on research performed on two-pion correlations in proton-proton collision and simulations of two-particle correlations for ALICE experiment at the Large Hadron Collider. Chajecki’s Ph.D. thesis focused on global conservation laws and two-particle correlations at the Relativistic Heavy Ion Collider. He then worked as a research associate at the National Superconducting Cyclotron Laboratory at Michigan State University.