Theory seminar: Jacob Spisak: Astrophysical searches for sterile neutrino and axion-like particle dark matter

Thursday 21 Mar 2024, 16:00 → 17:00 Europe/Amsterdam

In this talk I will discuss two dark matter candidates, sterile neutrinos and axion-like particles (ALPs). In the first part of my talk I will describe a novel mechanism for producing a cosmologically-significant relic density of sterile neutrinos. This scheme invokes a dark population transfer involving two (or more) sterile neutrinos, producing a dark matter candidate that can evade current electromagnetic and structure-based bounds, but may nevertheless be probed by future observations. In the second part of my talk I will pivot to a discussion of astrophysical searches for ALPs. Recently a detection technique using the CMB was proposed which relies on the fact that the ALP oscillates at a frequency set by its mass, leading to a time-dependent birefringence that may be observed in the polarization of the CMB. Using two years of data from the POLARBEAR telescope, we searched for this effect and placed a median 95% upper limit of 0.65 degrees on the sinusoid amplitude for oscillation periods between 2 days and 50 days.