Edward Hardy

Abstract:

In 2021 the Quantum Sensors for the Hidden Sector (QSHS) collaboration was founded in the UK and received funding to develop and demonstrate quantum devices with the potential to detect hidden sector particles in the μeV to 100 μeV mass window. The collaboration has been developing a range of devices. It is building a high-field, low-temperature facility at the University of Sheffield to characterise and test the devices in a haloscope geometry. This paper introduces the collaboration's motivation, aims, and progress.

Abstract:

Dark photon dark matter that has a kinetic mixing with the Standard Model photon can resonantly convert in environments where its mass 𝑚𝐴′ coincides with the plasma frequency. We show that such conversion in neutron stars or accreting white dwarfs in the Galactic Center can lead to detectable radio signals. Depending on the dark matter spatial distribution, future radio telescopes could be sensitive to values of the kinetic mixing parameter that exceed current constraints by orders of magnitude for 𝑚𝐴′ ∈(6×10−6,7×10−4)  eV.

Abstract:

An axion-like-particle (ALP) in the post-inflationary scenario with domain wall number N > 1 can be dark matter if the residual ℤN symmetry has a small explicit breaking. Although we cannot determine the full dynamics of the system reliably, we provide evidence that such an ALP can account for the observed dark matter abundance while having a relatively small decay constant and consequently a possibly large coupling to photons. In particular, we determine the number of domain walls per Hubble patch around the time when they form using numerical simulations and combine this with analytic expectations about the subsequent dynamics. We show that the strongest constraint on the decay constant is likely to come from the dark matter ALPs being produced with large isocurvature fluctuations at small spatial scales. We also comment on the uncertainties on the dark matter small-scale structure that might form from these overdensities, in particular pointing out the importance of quantum pressure in the N = 1 case.

Abstract:

The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to cover the available parameter space for weakly interacting massive particles, while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector.