From 2001 to 2003, Spiropulu continued on the CDF experiment as an Enrico Fermi fellow at the University of Chicago, using signatures of missing transverse energy to search for extra dimensions and supersymmetry. In 2004, she moved to CERN as a research scientist with the CMS experiment. For the years 2005 to 2008, she served as co-convener of the CMS physics analysis group searching for supersymmetry and other phenomena beyond the Standard Model. She was a senior research physicist at CERN until 2012, and has been professor of Physics at the California Institute of Technology since 2009. She invented, with her student Chris Rogan and collaborators Maurizio Pierini and Joseph Lykken, a new set of kinematic variables ("razor") targeting the discovery and characterization of new physics at the LHC.