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Yilda Boukhtouchen has successfully defended her PhD thesis. Her thesis’s title is "New Searches for Heavy and Composite Dark Matter”. Dr. Boukhtouchen carried out her research under the supervision of Prof. Joe Bramante. 

This thesis develops the observable signatures of heavy dark matter, focusing on models in which dark matter forms composite states bound by an attractive force, analogous to atomic nuclei. These composites can grow large, especially in the loosely bound regime that is the central focus here—where binding energy per constituent is much smaller than constituent mass. This thesis derives the distinct scattering regimes such composites exhibit as a function of binding energy (tied to size) and constituent mass, and identifies regions of parameter space where composites scatter multiple times during a single detector passage, producing a signature suited to multi-scattering analyses. Pushing into the extremely loosely bound regime, this thesis shows that successive recoils can fully disassemble a composite, and by modelling the resulting constituents' trajectories through the Earth, characterizes the cascade of particles reaching a detector, which is markedly different from a single heavier particle, and capable of producing multiple non-collinear scatters or correlated scatters across detectors. As a complementary probe, this thesis constructs a novel model of dark matter-driven baryonic feedback—in which heavy dark matter triggers excess Type Ia supernovae from collapsing white dwarfs—and incorporates it into galaxy simulations, demonstrating that this mechanism can suppress a dwarf galaxy's star formation rate and dark matter density profile, and in extreme cases, quench star formation entirely.

The plot shows the different DM-nucleus scattering regimes for composite dark matter with a total mass of 10¹⁵ GeV, and assuming a liquid argon target. The scattering regimes vary with constituent mass and with inter-constituent spacing, which is related to the binding energy. The detection phenomenology of such a composite is very closely linked to its scattering regime.