Distinguishing Dark Matter Stabilization Symmetries at Hadron Colliders with Mass Variables

Cosmological and astrophysical observations, yet all gravitational, suggest that there exists stable matter, so-called dark matter (DM), in our universe, which is exerting gravity but hardly detectable in relevant experiments. The stability of DM indicates that DM needs to be either massless or protected by a new symmetry (henceforth called DM stabilizing symmetry) preventing its decay. It turns out that cosmological consideration suggests that massless particles be unlikely to constitute a dominant portion of the DM, motivating DM candidates with a sizable mass. While a massive particle, in general, may decay into lighter particles, the charge conservation associated with the symmetry ensures the stability of DM. There is a tremendous amount of effort in the search for DM candidates and it also comprises collider experiments. DM is, by definition, hard to be detected at colliders such as the LHC. So, its existence may be inferred from (visible) Standard Model (SM) particles emitted from a decay chain of a heavier state (henceforth denoted as a DM partner) into DM. One compelling situation to be considered is a pair creation of DM partner particles followed by decay of each of those into DM particles. Different symmetries protecting the DM stability may allow different event topologies for the decaying process of the pair-produced partners. Although many well-motivated new physics models accompany a $Z_2$/parity-type symmetry as the DM stabilization symmetry, $Z_2$ is not the only option. My CERN summer student programme was devoted to constructing a systematic method for determining whether or not a given decay process is induced from a $Z_2$ symmetry, with limited information encoded in relevant visible states.