Speaker
Description
Ultralight Axion Like Particles (ALPs) can mediate a macroscopic force with long-range monopole-dipole interactions between the Earth and the Sun, if the Earth is treated as a polarized source. Due to the geomagnetic field, there exists an estimated $10^{42}$ polarized electrons within the Earth. These electrons, in a polarized state, can interact with the unpolarized nucleons in the Sun, giving rise to a monopole-dipole potential between the Sun-Earth system. This phenomenon ultimately influences the trajectories of light and celestial bodies, resulting in observable effects such as gravitational light bending, Shapiro time delay, and perihelion precession of planets. There are two scenarios for constraining the monopole-dipole coupling strength. In the first scenario, constraint on the monopole-dipole strength based on a single astrophysical observation, treating the Earth as a source of polarized electrons is established. The perihelion precession of Earth sets an upper limit on the monopole-dipole coupling strength as $g_Sg_P \,\lesssim 1.75\times 10^{-16}$ for the ALP of mass $m_a \, \lesssim 1.35\times 10^{-18}~\rm{eV}$. This bound surpasses the limits obtained from gravitational light bending and Shapiro time delay. In the second scenario, constraints on monopole-monopole coupling strength $g_S \, \left(\lesssim 3.51 \times 10^{-25}\right)$ arises from the perihelion precession of the planet Mars, while the limit on dipole-dipole coupling strength $g_P \, \left(\lesssim 1.6 \times 10^{-13}\right)$ is taken from the measurement of the tip of the red giant branch in $\omega$ Centauri using Gaia DR2 data. Together, they yield a hybrid constraint on the monopole-dipole coupling strength as $g_Sg_P \, \lesssim \, 5.61 \times 10^{-38}$. The hybrid bound is three orders of magnitude more stringent than the Eot-Wash experiment and one order of magnitude stronger than the current hybrid $(\rm{Lab})^N_S\times (\rm{Astro})^e_P$ limit.
| Track type | Astroparticle Physics |
|---|
