Recently, quantum states of ultra-cold neutrons in the Earth's gravitational field have been observed for the first time. From the fact that they are consistent with Newtonian gravity on the 10 %-level, analytical limits on alpha and lambda of short-range Yukawa-like additional interactions are derived between lambda = 1 micrometer and 1 mm. We arrive for lambda > 10 micrometer at alpha < 2 \cdot 10^11 at 90 % confidence level. This translates into a limit g_s g_p / (\hbar c) < 2 \cdot 10^{ -15} on the pseudo-scalar coupling of axions in the previously experimentally unaccessible astrophysical axion window.
Categories: hep-ph