Direct detections of the axionlike particle revisited

Axionlike particles (ALPs) are promising dark matter candidates. Their signals in direct detection experiments arise from the well-known inverse Primakoff effect or the inverse Compton scattering of ALPs with the electron. In this paper, we revisit the direct detection of ALP by carefully considering the interference between the inverse Primakoff amplitude and the inverse Compton amplitude in the scattering process $a+e\to e+\gamma$ for the first time. It shows that the contribution of the interference term turns to be dominated in the scattering for a large ALP energy. Given the new analytical formula, signals or constraints of ALP couplings in various projected experiments are investigated. Our results show that these experiments may put strong constraints on ALP couplings for relatively heavy ALP. We further study projected constraints on ALP from the JUNO experiment, which shows competitive constraints on ALP couplings using a ten-year exposure.

Figure 1

Tree-level Feynman diagrams illustrating (a) the inverse Primakoff process and (b), (c) the inverse Compton process.

Figure 2

The cross sections inverse Primakoff (blue dashed line), inverse Compton(red dashed line) and interference terms (green dashed line) conversion of ALP into photon. The black solid line represents the total cross section.

Figure 3

The blue line represents the solar axion flux produced by the ABC processes with $g_{ae}={10}^{-13}$ [17]. The orange line represents the solar axion flux generated by the Primakoff process with $g_{a\gamma }={10}^{-11}({\mathrm{GeV}}^{-1})$ [57, 58, 59]. Neutrino-boosted ALP flux is shown as green line with $m_a={10}^{-15}\mathrm{keV}$ [28]. Note that the green line has been scaled up by a factor ${10}^5$ to make it visible.

Figure 4

90% C.L. limits on axion-photon (axion-electron) coupling $g_{a\gamma }(g_{ae})$ versus ALP mass in the left (right) panel. The blue solid, cyan solid, and blue dashed lines represent constraints of direct detection experiments PandaX-4T, XENONnT, and PandaX-30T, respectively, applied to three different incoming ALP fluxes; neutrino-boosted ALP, solar axion, and Galactic ALP DM. For comparison, other search experiments including ALPS (red) [69], CAST (darker red) [14, 20], Beam dump (green) [70, 71, 72, 73, 74] and horizontal branch stars (brown) [21] are also shown in left panel. And there is stability constraint as ALP can decay into photons(gray dashed line). In right panel, the bounds from solar neutrino flux (green) [75] and red giants (darker green) [76], underground detectors SuperCDMS (darker red) [77] are added.

Figure 5

90% C.L. limits on axion-photon or axion-electron coupling constants versus ALP mass. We set $g_{ae}={10}^{-14}$ and $g_{a\gamma }=5.4\times {10}^{-16}({\mathrm{GeV}}^{-1})$ in left and right panel, respectively. The gray dashed line indicates the stability constraint.

Figure 6

90% C.L. limits on $g_{ae}–g_{a\gamma }$ plane in XENONnT and PandaX-30T. Gray lines represent the constraints from astrophysical bounds including red giants [78] and the horizontal branch stars [21], as well as the constraints from the solar neutrino [75], with arrows denoting excluded regions. We take $m_a={10}^{-4}\mathrm{keV}$ in the figure.

Figure 7

90% C.L. limits on $g_{a\gamma }(g_{ae})–m_a$ planes in JUNO. Left panel: Black solid (dashed) line represent $g_{ae}={10}^{-14}$ (${10}^{-13}$). Right panel: Black solid (dashed) line represents $g_{a\gamma }={10}^{-11}$ $({10}^{-10}){\mathrm{GeV}}^{-1}$.