Talk 1: Precision Probes of New Physics
Speaker: Surjeet Rajendran ( Johns Hopkins University)
Abstract: The existence of dark matter strongly suggests that there is new physics that might interact weakly with the standard model. The mass range of this new physics is ill constrained and can span many decades of energy. Given the vastness of the unknown, it is necessary to devise experiments that can probe large parts of this parameter space, while being mindful of the cost of such probes. If this new physics is light, a comprehensive experimental program to search for a variety of such particles over a broad range of energy appears possible. This program is enabled by the advances that have occurred in diverse fields of precision metrology (such as atom interferometry, superconducting quantum technologies etc) over the past few decades. In this talk, I will give examples of new experiments that have recently been proposed to search for axion dark matter using nonlinear crystals, short distance forces using Mossbauer spectroscopy, monopole-dipole forces between nucleons and electrons using atom interferometry and scalar-pseudo scalar interactions between matter and light using superconducting cavities.

Talk 2: Superfluid acoustic search for ultralight dark matter:
a newbie's perspective and prospects
Speaker: Jack Sankey, McGill University

Abstract: We know from multiple astrophysical observations that the vast majority of matter in our galaxy is of totally unknown nature, and, as such, its direct detection promises to revolutionize our understanding of the universe. For a well-motivated range of “ultralight dark matter” (UDM) candidates (peV-scale particle mass), superfluid helium represents an ideal, extraordinarily low-noise acoustic sensor that will place new and deep constraints on UDM, notably outperforming long-running experiments (e.g., Eot-Wash and LIGO-Virgo) after just an hour of operation. The current prototype (HeLIOS) relies on helium’s high-Q mechanical resonance to place deep constraints over a needle-thin (swept) range of frequencies. However, using our group's specialized membrane and fiber-cavity systems, we can create a pressure transducer capable of achieving the prototype's resonant sensitivity over the broad band, thereby covering previously inaccessible masses while turning years-long frequency sweeps into hours-long single acquisitions that are sensitive to transients. Moreover, the sensitivity floor exhibits notches at special frequencies (due to destructive interference canceling the UDM drive) that can also be swept to help validate candidate signals. Our long-term goal is to realize a global array of these “UDM antennas” to reject local noise sources and provide new information about the UDM “wind” direction.