Detecting Axion-like Particles with Plasmon in Reactor-based Experiment

Abstract

Axion and axion-like particles (ALPs), predicted by various extensions of the Standard Model, can be copiously produced in nuclear reactors via the Primakoff process. In this work, we explore the detection of such relativistic ALPs through the plasmon effect in silicon detectors located near reactors. Utilizing the data from the Connie and Atucha-II experiments, we set the 90\% confidence level upper limits on the ALP-photon coupling $g_{aγ}$ over the mass range $0.1< m_a <100$ keV. Furthermore, we present that the projected sensitivity of the Oscura experiment, with an exposure of 30 kg$\cdot$ yr, will surpass the current reach of the NEON experiment by approximately one order of magnitude in the same mass range. This improvement would substantially expand the explored region of the QCD axion and ALP parameter space.

Figures (4)

• Figure 1: The ALP flux at a detector located 30 m from the $3.95~\rm{GW_{th}}$ nuclear reactor is shown as the function of ALP energy $E_a$ for ALP masses $m_a =100 ~\rm eV$ (green solid lines), $m_a =10~\rm keV$ (orange solid lines) and $m_a =1 ~\rm MeV$ (blue solid lines). The ALP-photon coupling is set to $g_{a\gamma\gamma}=10^{-4} ~\rm GeV^{-1}$.
• Figure 2: The blue region illustrates the plasmonic energy loss function $\rm{Im}[-\epsilon^{-1}(Q, \omega)]>10^{-1}$ for silicon semiconductors on the plane of momentum transfer $Q$ and energy transfer $\omega$. The kinematically accessible regions for 100 eV and 1 keV ALP are shown for three incident velocities: $v_a=0.008c$ (red), $v_a=0.080c$ (green), and $v_a=0.800c$ (violet).
• Figure 3: The differential event rate $dR/d\omega$ as a function of the deposited energy $\omega$ for the plasmon effect, with an ALP with a mass of $40~\rm{ keV}$ and a coupling constant of $g_{a\gamma\gamma}=10^{-4}~\rm{GeV}^{-1}$, produced via the Primakoff process. The curves correspond to different experimental settings: Connie (blue), Atucha-II (orange), and Oscura (green).
• Figure 4: The 90% C.L. upper limits on the ALP-photon coupling as a function of the ALP mass. The blue solid, orange solid, and red dashed lines represent the limits from the Connie, Atucha-II, and projected Oscura experiments, respectively. For comparison, we also include existing limits from beam dump experiments Bechis:1979kp1987SearchBjorken:1988asBlumlein:1991xhAndreas:2010msCCM:2021jmk, the NEON experiment NEON:2024kwv, $e^{+}e^{-}\rightarrow \gamma+\rm{invisible}$Jaeckel:2015jla and the parameter space favored by a representative QCD axion model DiLuzio:2020wdo.