Speaker
Description
Ultralight dark matter with quadratic couplings to the Standard Model need not have a homogeneous local profile. Scattering on macroscopic bodies can distort the field configuration near Earth and, for sufficiently large couplings, the atmosphere acts as an efficient shield. I will discuss this effect in the context of clock searches and show that space-based platforms offer a natural way around it. When the orbital altitude exceeds the dark-matter de Broglie wavelength, the orbit-averaged field amplitude is restored to its unscattered value.
In addition, for $m_{\rm DM} \gtrsim 10^{-10}\,\mathrm{eV}$, when the de Broglie wavelength becomes shorter than Earth’s radius, the dark-matter profile near Earth develops a dipole structure. For clocks in low Earth orbit, this produces a characteristic temporal modulation that can enhance sensitivity and provide a nontrivial cross-check of the signal interpretation. I will show that optical clocks on the ISS can set leading bounds in some regimes, and that future orbiting nuclear clocks could extend the reach further into parameter space inaccessible to ground-based searches.