Title: Searching for axion-like particles using black holes and pulsars

Speaker: Dr. Yue Zhao (Utah University)

Time: 2:00 PM, May 20th (Monday), 2019

Place: R319, Theoretical Physics Division

Abstract：Axion-like particles are among the most popular candidates for new physics beyond Standard Model. An axion background can induce the oscillation of the position angle for a linearly polarized photon, due to birefringence effect. We propose two ways to look for such an effect. First, with high spatial resolution, polarimetric imaging of a supermassive black hole, like M87* or Sgr A* , by the Event Horizon Telescope can be used to probe the existence of an axion field. The axion can accumulate around a rotating black hole through superradiance mechanism, forming an axion cloud. The supermassive black hole M87* (Sgr A*) can probe axions with masses O(10^-20) eV (O(10^-17) eV) and decay constant smaller than O(10^16) GeV. In addition, linearly polarized pulsar light can also be used as a probe. We show that this can potentially serach for an axion-photon coupling as small as ~10^-13 GeV^-1 for axion mass ~10^-22-10^-20 eV, given the current measurement accuracy.