Search

We introduce an approach to search for low-mass pseudo Nambu–Goldstone bosons as candidates for dark components in the Universe via stimulated resonant photon scattering by utilizing high-intensity lasers and more generally coherent light sources. We then review sensitivity projections when nearly Fourier transform limited short pulse high-intensity light sources are assumed. We will put a special emphasis on the high-intensity laser available at the Extreme-Light-Infrastructure Nuclear Physics (ELI-NP) and provide a summary of the present activities at ELI-NP as a collaboration for an international joint experiment, SAPPHIRES (Search for Axion-like Particles via optical Parametric effects with High-Intensity laseRs in Empy Space). [ABSTRACT FROM AUTHOR]

Sub-eV axion-like particles (ALPs) have been searched for by focusing two-color near-infrared pulse lasers into a vacuum along a common optical axis. Within the focused quasi-parallel collision system created by combining a creation field (2.5 mJ/47 fs Ti:Sapphire laser) and a background inducing field (1.5 mJ/9 ns Nd:YAG laser), the detection of signal photons via stimulated resonant photon-photon scattering by exchanging ALPs was attempted in a vacuum chamber. The signal wavelength can be determined via energy-momentum conservation in the vacuum, and it coincides with that determined from the atomic four-wave-mixing (aFWM) process. In this work, the pulse energies were one order of magnitude higher than those in the previous search, allowing aFWM from optical elements to be observed as a pressure-independent background for the first time, in addition to the residual-gas-originating aFWM following a quadratic pressure dependence. In principle the four-wave-mixing process in vacuum via ALP exchanges (vFWM) must also be pressure-independent, so the development of a new method for discriminating the optical-element aFWM is indispensable for increasing the pulse energies to the values needed for future upgraded searches. In this paper, we will present the established method for quantifying the yield from the optical-element aFWM process based on the beam cross- section dependence. With the new method, the number of signal photons was found to be consistent with zero. We then successfully obtained a new exclusion region in the relation between ALP-photon coupling, g/M, and the ALP mass m, reaching the most sensitive point g/M = 1.14 × 10−5 GeV−1 at m = 0.18 eV. [ABSTRACT FROM AUTHOR]