Vector Dark Matter Detection using the Quantum Jump of Atoms

The hidden sector U(1) vector bosons created from inflationary fluctuations can be a substantial fraction of dark matter if their mass is around $10^{-5}$eV. The creation mechanism makes the vector bosons' energy spectral density $\rho_{cdm}/\Delta E$ very high. Therefore, the dark electric dipole transition rate in atoms is boosted if the energy gap between atomic states equals the mass of the vector bosons. By using the Zeeman effect, the energy gap between the 2S state and the 2P state in hydrogen atoms or hydrogen like ions can be tuned. The $2S$ state can be populated with electrons due to its relatively long life, which is about $1/7$s. When the energy gap between the semi-ground $2S$ state and the 2P state matches the mass of the cosmic vector bosons, induced transitions occur and the 2P state subsequently decays into the 1S state. The $2P\to1S$ decay emitted Lyman-$\alpha$ photons can then be registered. The choices of target atoms depend on the experimental facilities and the mass ranges of the vector bosons. Because the mass of the vector boson is connected to the inflation scale, the proposed experiment may provide a probe to inflation.Comment: 5 pages, 3 figures; references added; matches version published in PL

Probe Dark Matter Axions using the Hyperfine Structure Splitting of Hydrogen Atoms

The cosmological axions can be a substantial part of dark matter if their PQ scale $f_a\sim10^{11}$GeV and mass $m_a\sim10^{-5}$eV. Because the axions were created from the misalignment mechanism, their energy spectral density is large. The axion induced atomic transitions consequently are boosted if the atomic energy gap matches with the axion mass. The hyperfine splitting between the spin 0 singlet ground state and the spin 1 triplet state of hydrogen is $0.59\times10^{-5}$eV, which is close to the mass of dark matter axions. With some additional adjustment by the Zeeman effect, quantum transitions could be induced between these states. Since the total spin of the triplet and the singlet differs one, the axion induced transitions might be countable with a Stern-Gerlach apparatus.Comment: 5 pages, 4 figures; discussions extended; some typos fixed; references adde

Broadband Dark Matter Axion Detection using a Cylindrical Capacitor

The cosmological axions/axion-like particles can compose a significant part of dark matter, however the uncertainty of their mass is large. Here we propose to search the axions using a cylindrical capacitor, in which the static electric field converts dark matter axions into an oscillating magnetic field. Using a static electric field can greatly reduce the magnetic field background compared to using the $\vec B$ field that the thermal current in the magnet-coil could be hard to annihilate. A cylindrical setup shields the electric field to the laboratory as well as encompasses the axion induced magnetic field within the capacitor, which results an increased magnetic field strength. The induced oscillating magnetic field then can be picked up by a SQUID-based magnetic-meter. Adding a superconductor ring-coil system into the induced magnetic field region can further boost the sensitivity and maintain the axion dark matter inherent bandwidth. The proposed setup is capable of a wide mass range searches as the signal can also be modulated by adjusting the angle between the electric field and the axion flow.Comment: 4 pages, 2 figure

The Minimal UV-induced Effective QCD Axion Theory

The characteristic axion couplings could be generated via effective couplings between the Standard Model (SM) fermions to a pseudo-Goldstone from a high-scale $U(1)$ Peccei-Quinn (PQ) symmetry breaking. Assuming that the UV-induced effective operators generate necessary couplings before the PQ symmetry breaking, and any low-scale couplings to the SM are restricted to the Yukawa sector, three minimal natural scenarios can be formulated, which provides a connection between the QCD-axions and mediators at the GUT/string scales. We find that the PQ symmetry breaking scale could be about $10^{15}$ GeV, higher than the classical QCD dark matter axion window but possible if the anthropic window is considered. We also propose an experiment to probe such scenarios. If the dark matter axion is discovered, they might suggest that we live in an atypical Hubble volume.Comment: 4 page