Title: Picolensing as a probe of massive compact DM states


Abstract: Compact supermassive dark-matter states act as gravitational lenses. Widely spatially separated space-based gamma-ray detectors would observe parallax of such an intervening lens with respect to cosmologically distant gamma-ray bursts (GRB). This parallax can be of order the Einstein angle of the lens, resulting in a significant differential magnification of the source as viewed from the two detectors. Simultaneous brightness measurements of the same GRB made by two detectors can therefore detect or exclude such DM states, via this so-called “picolensing” effect. Recent studies have shown this approach could be a promising way to search in particular for primordial black hole (PBH) dark matter in part of the “asteroid mass window”, roughly 1e-15 < M_{PBH}/ M_{Sun} < 1e-10. In this talk, I will discuss my work to explore the robustness of this signal to various uncertainties not previously carefully accounted for: most importantly, to uncertainties in the transverse extent of the observed GRB emission region. I’ll show that, while large GRB source-size uncertainties do degrade previous projections somewhat, it is still possible to probe most of the PBH DM asteroid mass window with a future mission that employs two Swift/BAT-class detectors separated by a distance on the order of an AU. Depending on the total number of GRBs that such a mission ultimately observes, it may even be possible to robustly probe new subcomponent dark-matter parameter space at PBH masses above the window, potentially as high as 2e-8 M_{Sun}. Time permitting, I will also discuss ongoing work to extend this observable to detect QCD axion miniclusters.

https://lbnl.zoom.us/j/94928022788?pwd=emVQWG1mTnhSbHVqekVuenk0VEVQZz09