KMT-2023-BLG-2669: Ninth Free-floating Planet Candidate with θE measurements

We report a free-floating planet (FFP) candidate identified from the analysis of the microlensing event KMT-2023-BLG-2669. The lensing light curve is characterized by a short duration ( 3\, days) and a small amplitude ( 0.7\, mag). From the analysis, we find the Einstein timescale of tE 0.33\, days and the Einstein radius of θE 4.41\,μ as. These measurements enable us to infer the lens mass as M = 8\,M⊕ (πᵣₑₗ / 0.1\, mas)⁻¹, where πᵣₑₗ is the relative lens-source parallax. The inference implies that the lens is a sub-Neptune- to Saturn-mass object depending on its unknown distance. This is the ninth isolated planetary-mass microlens with θE < 10\,μ as, which (as shown by {gould22}) is a useful threshold for a FFP candidate. We conduct extensive searches for possible signals of a host star in the light curve, but find no strong evidence for the host. We discuss the possibility of using late-time high-resolution imaging to probe for possible hosts.