A search for dark matter axions with masses >10μeV/c2 has been performed using the HAYSTAC experiment's squeezed state receiver to achieve sub-quantum limited noise. This report includes details of the design and operation of the experiment previously used to search for axions in the mass ranges 16.96−17.12 and 17.14−17.28μeV/c2(4.100−4.140GHz) and 4.145−4.178GHz) as well as upgrades to facilitate an extended search at higher masses. These upgrades include improvements to the data acquisition routine which have reduced the effective dead time by a factor of 5, allowing for the new region to be scanned ∼1.6 times faster with comparable sensitivity. No statistically significant evidence of an axion signal is found in the range 18.44−18.71μeV/c2(4.459−4.523GHz), leading to an aggregate upper limit exclusion at the 90% level on the axion-photon coupling of 2.06×gγKSVZ.
@article{arxiv.2301.09721,
title = {New Results from HAYSTAC's Phase II Operation with a Squeezed State Receiver},
author = {HAYSTAC Collaboration and M. J. Jewell and A. F. Leder and K. M. Backes and Xiran Bai and K. van Bibber and B. M. Brubaker and S. B. Cahn and A. Droster and Maryam H. Esmat and Sumita Ghosh and Eleanor Graham and Gene C. Hilton and H. Jackson and Claire Laffan and S. K. Lamoreaux and K. W. Lehnert and S. M. Lewis and M. Malnou and R. H. Maruyama and D. A. Palken and N. M. Rapidis and E. P. Ruddy and M. Simanovskaia and Sukhman Singh and D. H. Speller and Leila R. Vale and H. Wang and Yuqi Zhu},
journal= {arXiv preprint arXiv:2301.09721},
year = {2023}
}