Periodic Reporting for period 1 - NLO-DM (New Light On Dark Matter)
Reporting period: 2023-02-01 to 2025-07-31
Dark matter (DM) makes up most of the Universe’s matter, but its particle nature remains largely unkown. While large-scale observations strongly support a cold DM paradigm, DM may not be strictly collisionless. This motivates the concept of self-interacting DM, where DM scatterings help reconcile small-scale observations. If these collisions also dissipate energy (e.g. by radiating hidden particles), halo cooling and denser structures could ensue—a possibility rarely addressed in depth. One major aim here is to develop a comprehensive theoretical framework for such dissipative SIDM processes, and to investigate, whether they yield observable astrophysical or cosmological signals.
On the experimental side, as null searches for electroweak mass DM persist and attention shifts to sub-GeV DM, the experiments increasingly rely on rare secondary, but irreducible effects—for instance, the emission of soft photons (bremsstrahlung) or electrons (Migdal effect) during DM–nucleus scattering. These subtle processes can reveal energy transfers of lighter DM candidates, that otherwise go undetected. However, many existing calculations use simplifying assumptions that may fail under more general conditions. Our project seeks to put these direct-detection signals on solid footing, in a way that the full quantum and atomic/solid-state physics is captured. This will reinforce the interpretation of experimentally reported results.
By unifying advanced astrophysical and experimental approaches, the aim is to broaden the search window for DM and to equip the community with robust tools to interpret an eventual DM signal.
On the experimental side, as null searches for electroweak mass DM persist and attention shifts to sub-GeV DM, the experiments increasingly rely on rare secondary, but irreducible effects—for instance, the emission of soft photons (bremsstrahlung) or electrons (Migdal effect) during DM–nucleus scattering. These subtle processes can reveal energy transfers of lighter DM candidates, that otherwise go undetected. However, many existing calculations use simplifying assumptions that may fail under more general conditions. Our project seeks to put these direct-detection signals on solid footing, in a way that the full quantum and atomic/solid-state physics is captured. This will reinforce the interpretation of experimentally reported results.
By unifying advanced astrophysical and experimental approaches, the aim is to broaden the search window for DM and to equip the community with robust tools to interpret an eventual DM signal.
Dissipative SIDM Framework (in preparation)
We are developing a comprehensive theoretical description of DM self-collisions that radiate energy. By examining multiple models with both, short- and long-range forces, with massless or light mediating particles, we are finding a unifying description at leading order in the collision velocity of these particles. Our general formulas provide comprehensive radiative cooling rates in easy analytical form, making it far easier to implement them in astrophysical or cosmological simulations.
Time-Resolved Migdal Effect Theory (in preparation)
We are constructing a quantum mechanical approach of prompt electron ionziation from DM-nuclear scatterings that covers all kinematic regimes. In particular, a critical parameter entering the considerations is how long a DM–nucleus interaction lasts. This goes beyond the usual "instantaneous jolt" assumption, which can fail if DM interacts over a longer range. Our preliminary results show that the standard impulse approximation can overestimate the ionization efficiency for "slower'' collisions. A treatment that reveals this adiabatic crossover will directly impact future analyses of low-threshold DM experiments.
SIDM Dark Matter with Bound-State Catalysis (published, Phys.Rev.Lett.)
We showed how bound states of self-scattering strongly interacting DM can catalyze dark matter freeze out, enabling new processes once thought to require three initial DM particles. This “bound-state-assisted” freeze-out mechanism demonstrates that even conventional two-body annihilations can be effective if bound states are present, broadening the range of viable SIMP scenarios.
We are developing a comprehensive theoretical description of DM self-collisions that radiate energy. By examining multiple models with both, short- and long-range forces, with massless or light mediating particles, we are finding a unifying description at leading order in the collision velocity of these particles. Our general formulas provide comprehensive radiative cooling rates in easy analytical form, making it far easier to implement them in astrophysical or cosmological simulations.
Time-Resolved Migdal Effect Theory (in preparation)
We are constructing a quantum mechanical approach of prompt electron ionziation from DM-nuclear scatterings that covers all kinematic regimes. In particular, a critical parameter entering the considerations is how long a DM–nucleus interaction lasts. This goes beyond the usual "instantaneous jolt" assumption, which can fail if DM interacts over a longer range. Our preliminary results show that the standard impulse approximation can overestimate the ionization efficiency for "slower'' collisions. A treatment that reveals this adiabatic crossover will directly impact future analyses of low-threshold DM experiments.
SIDM Dark Matter with Bound-State Catalysis (published, Phys.Rev.Lett.)
We showed how bound states of self-scattering strongly interacting DM can catalyze dark matter freeze out, enabling new processes once thought to require three initial DM particles. This “bound-state-assisted” freeze-out mechanism demonstrates that even conventional two-body annihilations can be effective if bound states are present, broadening the range of viable SIMP scenarios.
Unified Dissipative DM Treatment:
We produced the first broad framework unifying many dissipative SIDM models. Rather than deriving scattered, model-specific formulas, researchers can now apply our general analytic results. This opens the door to systematically incorporating energy-radiation effects into simulations of galactic and cosmological structure.
Extended Migdal Effect Modeling:
Traditional calculations assumed a sudden nuclear recoil; our new method continuously interpolates between adiabatic (no ionization) and impulsive (max ionization) limits. Thereby, we identify the regime where the standard approximation breaks down. In consequence, this will allow for a more robust interpretation of low-energy signals in current and future detectors.
Catalyzed SIDM genesis through bound states:
The finding that lower-order annihilation can proceed if bound states exist significantly broadens the theoretical landscape for strongly coupled dark sectors. It also clarifies how composite or bound-state effects can influence DM’s cosmological abundance, providing new, testable scenarios that were not foreseen in conventional SIMP frameworks
We produced the first broad framework unifying many dissipative SIDM models. Rather than deriving scattered, model-specific formulas, researchers can now apply our general analytic results. This opens the door to systematically incorporating energy-radiation effects into simulations of galactic and cosmological structure.
Extended Migdal Effect Modeling:
Traditional calculations assumed a sudden nuclear recoil; our new method continuously interpolates between adiabatic (no ionization) and impulsive (max ionization) limits. Thereby, we identify the regime where the standard approximation breaks down. In consequence, this will allow for a more robust interpretation of low-energy signals in current and future detectors.
Catalyzed SIDM genesis through bound states:
The finding that lower-order annihilation can proceed if bound states exist significantly broadens the theoretical landscape for strongly coupled dark sectors. It also clarifies how composite or bound-state effects can influence DM’s cosmological abundance, providing new, testable scenarios that were not foreseen in conventional SIMP frameworks