MHz gravitational wave constraints with decameter Michelson interferometers

Abstract

A new detector, the Fermilab Holometer, consists of separate yet identical 39-meter Michelson interferometers. Strain sensitivity achieved is better than 10⁻²¹/√H̅z̅ between 1 to 13 MHz from a 130-hr dataset. This measurement exceeds the sensitivity and frequency range made from previous high frequency gravitational wave experiments by many orders of magnitude. Constraints are placed on a stochastic background at 382 Hz resolution. The 3σ upper limit on Ω_(GW), the gravitational wave energy density normalized to the closure density, ranges from 5.6 × 10¹² at 1 MHz to 8.4 × 10¹⁵ at 13 MHz. Another result from the same dataset is a search for nearby primordial black hole binaries (PBHB). There are no detectable monochromatic PBHBs in the mass range 0.83 - 3.5 × 10²¹ g between the earth and the moon. Projections for a chirp search with the same dataset increases the mass range to 0.59−2.5 × 10²⁵ g and distances out to Jupiter. This result presents a new method for placing limits on a poorly constrained mass range of primordial black holes. Additionally, solar system searches for PBHBs place limits on their contribution to the total dark matter fraction.

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