Improved Theoretical Predictions of Microlensing Rates for the Detection
  of Primordial Black Hole Dark Matter
  Primordial Black Holes (PBHs) remain a Dark Matter (DM) candidate of the
Standard Model of Particle Physics. Previously, we proposed a new method of
constraining the remaining PBH DM mass range using microlensing of stars
monitored by NASA's Kepler mission. We improve this analysis using a more
accurate treatment of the population of the Kepler source stars, their
variability and limb-darkening. We extend the theoretically detectable PBH DM
mass range down to $2\times10^{-10} M_\sun$, two orders of magnitude below
current limits and one third order of magnitude below our previous estimate. We
address how to extract the DM properties such as mass and spatial distribution
if PBH microlensing events were detected. We correct an error in a well-known
finite-source limb-darkening microlensing formula and also examine the effects
of varying the light curve cadence on PBH DM detectability. We also introduce
an approximation for estimating the predicted rate of detection per star as a
function of the star's properties, thus allowing for selection of source stars
in future missions, and extend our analysis to planned surveys, such as WFIRST.
