The role of parity in pseudo-Dirac inelastic dark matter

We investigate the role of parity violation in inelastic dark matter (iDM) models featuring pseudo-Dirac fermions coupled through vector and scalar portals. By relaxing the usual assumption of parity conservation, we develop the not-so-inelastic Dark Matter (niDM) framework, which continuously interpolates between the Dirac, inelastic, and Majorana dark matter limits. In the dark photon–mediated scenario, parity violation generates small but nonzero diagonal couplings that enable large mass splittings while maintaining viable parameter space, much of which can be explored by current collider experiments such as Belle~II. In the scalar portal case, parity violation reduces the number of degrees of freedom, leading to a minimal fermionic iDM realization—minimal-inelastic Dark Matter (miDM)—which provides an s-wave thermal target and a promising benchmark for future direct detection experiments like DARWIN. Overall, our results demonstrate that parity violation can open new predictive and testable regions of thermal dark matter parameter space, emphasizing the complementarity between collider, direct, and cosmological probes in exploring dark sectors.