  The IceCube Neutrino Observatory relies on an array of photomultiplier tubes
to detect Cherenkov light produced by charged particles in the South Pole ice.
IceCube data analyses depend on an in-depth characterization of the glacial
ice, and on novel approaches in event reconstruction that utilize fast
approximations of photoelectron yields. Here, a more accurate model is derived
for event reconstruction that better captures our current knowledge of ice
optical properties. When evaluated on a Monte Carlo simulation set, the median
angular resolution for in-ice particle showers improves by over a factor of
three compared to a reconstruction based on a simplified model of the ice. The
most substantial improvement is obtained when including effects of
birefringence due to the polycrystalline structure of the ice. When evaluated
on data classified as particle showers in the high-energy starting events
sample, a significantly improved description of the events is observed.
