Abstract:
One of the biggest challenges in fundamental physics is understanding the microscopic nature of dark matter. Scalar ultralight dark matter (ULDM) is a well-motivated extension to the standard model (SM) of particle physics, hypothesized to couple to SM parameters like the electron mass and the fine-structure constant, thereby inducing coherent oscillations in the size of macroscopic solids at the ULDM Compton frequency.
This talk presents the first experimental demonstration of a novel optomechanical ULDM sensor that employs two cryogenic sapphire Fabry-Pérot optical cavities. This apparatus leverages the cavities' longitudinal mechanical resonances to achieve sensitivity to differential cavity length variations induced by ULDM.
A four-day observation period with this sensor achieved an improvement of up to two orders of magnitude in the limits to ULDM coupling to the SM for the ULDM's Compton frequencies ranging from 5 kHz to 100 kHz. This was demonstrated for both the galactic halo and the Earth-bound relaxion halo models. This work represents a crucial step towards future upgrades, which are projected to yield an improvement of up to five orders of magnitude over a wider frequency range (100 Hz to 1 MHz), ultimately surpassing the theoretical naturalness threshold.
Speaker: Tejas Deshpande, Northern Arizona University
Faculty host: Tim Kovachy
Keywords: CFP, Physics