Collaborative Research: HAYSTAC Post-Inflation

About This Grant

The current scientific understanding of the Universe, based on astronomical observations, indicates that the total mass consists of about 5% ordinary matter. The remaining mass is made up of what we call "invisible" matter, which includes dark matter and dark energy. Dark matter forms an unseen halo around and throughout our galaxy, and it even exists in laboratories here on Earth. This type of matter makes up most of the galaxy's mass. Scientists believe that dark matter is likely a new kind of particle that has a very low mass and interacts very little with ordinary matter, except through gravity. One proposed candidate for dark matter is the Axion. This particle is thought to be connected to the strong nuclear force and its symmetries. It has a mass that is less than one billionth of that of a typical electron. When Axions in the galactic halo are exposed to a strong magnetic field, they can change into ordinary photons, which we detect as radio waves using very sensitive radio receivers that utilize advanced measurement techniques. The challenge lies in the fact that we do not know the exact frequency of these signals. Our research involves slowly tuning the receiver frequency to find the right one. Our project, named HAYSTAC, which stands for "Haloscope at Yale Sensitive to Cold (Dark Matter)," is a leading experiment in this area. Detecting dark matter in the form of Axions would be one of the most significant scientific breakthroughs in history. This research supports national interests by fostering scientific expertise and technologies that have wide-ranging applications. Additionally, this work provides excellent training for students in precision, reliability, and high sensitivity in instrumentation and technology. Understanding the nature of dark matter is one of the most important scientific questions of our time, and it is crucial for our nation to comprehend the dominant form of matter in our galaxy and the Universe as a whole. Astrophysical and cosmological data now point convincingly to a large component of Cold Dark Matter in the Universe, for which a light axion is a well-motivated candidate. Dark matter axions may be detected through their conversion to a narrow radio frequency signal in a microwave-cavity resonator permeated by a magnetic field. A three-institution collaboration has built and operated HAYSTAC, a small experiment that has served as an innovation test-bed for the new cavity designs and quantum-enhanced photon detection schemes above 15 micro-eV axion mass, corresponding to frequencies above 3.6 GHz. Since reporting the first-ever implementation of a Squeezed- State Receiver (SSR) used for data production (Nature, 2021), HAYSTAC remains the only dark matter axion experiment to circumvent the Standard Quantum Limit (SQL) of measurement sensitivity. Along with Advanced LIGO, it is one of only two experiments to do so in the context of astrophysical data production. HAYSTAC in its current form has operated stably for a year, resulting in a null scan of about 1 GHz. For the next phase (III) of HAYSTAC, a new quantum enhancement scheme has been developed and will be deployed – Cavity Entanglement And State Exchange For Improved Readout Efficiency (CEASEFIRE). Whereas the current HAYSTAC SSR yields a factor of 2 times scan rate enhancement, CEASEFIRE has demonstrated a factor of 8 times enhancement; this is transformational technology for the search for dark matter axions. Equally significant achievements have been made on resonator R&D. This award will support the operation and physics publication of HAYSTAC Phase III, which will open the search for axions in the mass range of 24–32 micro-eV (6–8 GHz). The first data run will demonstrate operation of a tunable lattice resonator in which the TM010 mode can be tuned over the entire spectrum without interference from TE modes. The award will also support HAYSTAC Phase IV, using the CEASEFIRE system in the 8–10 GHz range to achieve greater sensitivity and scan rate. The team will also develop searches for other physics, including cosmic axion background and new high-resolution analysis channel. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.