Speaker
Description
The nature of dark matter in the Universe is still an open question in
astrophysics and cosmology. Axions and axion-like particles (ALPs) offer a
compelling solution, and traditionally ground-based experiments have eagerly,
but to date unsuccessfully, searched for these hypothetical low-mass particles
that are expected to be produced in large quantities in the strong
electromagnetic fields in the interior of stars. In this talk, I offer a fresh look
at axions and ALPs by leveraging their conversion into X-rays in the magnetic
field of the Sun's atmosphere rather than a laboratory magnetic field. Unique
data acquired with the Nuclear Spectroscopic Telescope Array (NuSTAR) during
the solar minimum in 2020 allows to set stringent limits on the coupling of
axions to photons using state-of-the-art magnetic field models of the solar
atmosphere. I report pioneering limits on the axion-photon coupling strength
of $6.9\times 10^{-12}$ GeV$^{-1}$ at 95% confidence level for axion masses
$m_a \lesssim 2\times 10^{-7}$ eV, surpassing current ground-based searches and
further probing unexplored regions of the axion-photon coupling parameter space
up to axion masses of $m_a \lesssim 5\times 10^{-4}$ eV.
