No abstract

No abstract

We have searched for axion-like resonance states by colliding optical photons in a focused laser field (creation beam) by adding another laser field (inducing beam) for stimulation of the resonance decays, where frequency-converted signal photons can be created as a result of stimulated photonphoton scattering via exchanges of axion-like resonances. A quasi-parallel collision system (QPS) in such a focused field allows access to the sub-eV mass range of resonance particles. In past searches in QPS, for simplicity, we interpreted the scattering rate based on an analytically calculable symmetric collision geometry in both incident angles and incident energies by partially implementing the asymmetric nature to meet the actual experimental conditions. In this paper, we present new search results based on a complete parameterization including fully asymmetric collisional geometries. In particular, we combined a linearly polarized creation laser and a circularly polarized inducing laser to match the new parameterization. A 0.10-mJ/36-fs Ti:sapphire laser pulse and a 0.20-mJ/9ns Nd:YAG laser pulse were spatiotemporally synchronized by sharing a common optical axis and focused into the vacuum system. Under a condition in which atomic background processes were completely negligible, no significant scattering signal was observed at the vacuum pressure of 2.6 × 10 −5 Pa, thereby providing upper bounds on the coupling-mass relation by assuming exchanges of scalar and pseudoscalar fields at a 95% confidence level in the sub-eV mass range.

A mechanism of cavity-induced pressure oscillation in supersonic flows is not well understood in spite of a lot of former investigations. Especially, the process by which the pressure wave is generated and the path of the pressure wave propagating inside the cavity remain unclear. In order to clarify these, the oscillatory behaviors in the supersonic flow over a rectangular cavity are visualized by the schlieren method with a high-speed camera in the present study. The inlet Mach number of the flow is 1.68. The length and depth of the cavity are 14.0mm and 11.7mm respectively; i.e., the length-to-depth ratio of the cavity is 1.20. The pressure oscillation near the trailing edge of the cavity is also measured by use of the semiconductor-type pressure transducer simultaneously with the visualization. As a result, the pressure waves propagating inside as well as outside the cavity are successfully visualized. In addition, the relationship between the shear layer displacement, pressure wave generation and pressure oscillation at the trailing edge of the cavity are clarified experimentally.

No abstract