New Directions for Axion Searches via Scattering at Reactor Neutrino Experiments

New Directions for Axionlike Particle Searches Combining Nuclear Reactors and Haloscopes

In this Letter, we propose reactoscope, a novel experimental setup for axionlike particle (ALP) searches. Nuclear reactors produce a copious number of photons, a fraction of which could convert into ALPs via Primakoff process in the reactor core. The generated flux of ALPs leaves the nuclear power plant and its passage through a region with a strong magnetic field results in the efficient conversion to photons that can be detected. Such magnetic field is the key component of axion haloscope experiments. Adjacent nuclear reactor and axion haloscope experiments exist in Grenoble, France. There, the Institut Laue-Langevin research reactor is situated only ∼700  m from GrAHal, the axion haloscope platform designed to offer several volume and magnetic field (up to 43 T) configurations. We derive sensitivity projections for photophilic ALP searches with the institute and GrAHal, and also scrutinize analogous realizations, such as the one comprising the Axion Solar Telescope experiment at CERN and the Bugey nuclear power plant. The results that we obtain complement and extend the reach of existing laboratory experiments, e.g., the light-shining-through-walls experiment. While the derived sensitivities are not competitive when compared to the astrophysical limits, our analysis is free from the assumptions associated with those limits.

Axionlike Particles at Future Neutrino Experiments: Closing the Cosmological Triangle

Axionlike particles (ALPs) provide a promising direction in the search for new physics, while a wide range of models incorporate ALPs. We point out that future neutrino experiments, such as DUNE, possess competitive sensitivity to ALP signals. The high-intensity proton beam impinging on a target can not only produce copious amounts of neutrinos, but also cascade photons that are created from charged particle showers stopping in the target. Therefore, ALPs interacting with photons can be produced (often energetically) with high intensity via the Primakoff effect and then leave their signatures at the near detector through the inverse Primakoff scattering or decays to a photon pair. Moreover, the high-capability near detectors allow for discrimination between ALP signals and potential backgrounds, improving the signal sensitivity further. We demonstrate that a DUNE-like detector can explore a wide range of parameter space in ALP-photon coupling g_{aγ} vs ALP mass m_{a}, including some regions unconstrained by existing bounds; the "cosmological triangle" will be fully explored and the sensitivity limits would reach up to m_{a}∼3-4  GeV and down to g_{aγ}∼10^{-8}  GeV^{-1}.

Neutrino Self-Interactions and XENON1T Electron Recoil Excess

The XENON1T collaboration recently reported an excess in electron recoil events in the energy range between 1-7 keV. This excess could be understood to originate from the known solar neutrino flux if neutrinos couple to a light vector mediator with strength g_{νN} that kinetically mixes with the photon with strength χ and g_{νN}χ∼10^{-13}. Here, we show that such coupling values can naturally arise in a renormalizable model of long-range vector-mediated neutrino self-interactions. The model could be distinguished from other explanations of the XENON1T excess by the characteristic 1/T^{2} energy dependence of the neutrino-electron scattering cross section. Other signatures include invisible Higgs and Z decays and leptophilic charged Higgses at a few 100 GeV. ALPS II will probe part of the viable parameter space.

Inverse Primakoff Scattering as a Probe of Solar Axions at Liquid Xenon Direct Detection Experiments

We show that XENON1T and future liquid xenon (LXe) direct detection experiments are sensitive to axions through the standard g_{aγ}aFF[over ˜] operators due to inverse-Primakoff scattering. This previously neglected channel significantly improves the sensitivity to the axion-photon coupling, with a reach extending to g_{aγ}∼10^{-10}  GeV^{-1} for axion masses up to a keV, thereby extending into the region of heavier QCD axion models. This result modifies the couplings required to explain the XENON1T excess in terms of solar axions, opening a large region of g_{aγ}-m_{a} parameter space that is not ruled out by the CAST helioscope experiment and reducing the tension with the astrophysical constraints. We explore the sensitivity to solar axions for future generations of LXe detectors that can exceed future helioscope experiments, such as IAXO, for a large region of parameter space.