  HR4796A hosts a well-studied debris disk with a long history due to its high
fractional luminosity and favorable inclination lending itself well to both
unresolved and resolved observations. We present new J- and K1-band images of
the resolved debris disk HR4796A taken in the polarimetric mode of the Gemini
Planet Imager (GPI). The polarized intensity features a strongly forward
scattered brightness distribution and is undetected at the far side of the
disk. The total intensity is detected at all scattering angles and also
exhibits a strong forward scattering peak. We use a forward modelled geometric
disk in order to extract geometric parameters, polarized fraction and total
intensity scattering phase functions for these data as well as H-band data
previously taken by GPI. We find the polarized phase function becomes
increasingly more forward scattering as wavelength increases. We fit Mie and
distribution of hollow spheres grain (DHS) models to the extracted functions.
We find that while it is possible to describe generate a satisfactory model for
the total intensity using a DHS model, but not with a Mie model. We find that
no single grain population of DHS or Mie grains of arbitrary composition can
simultaneously reproduce the polarized fraction and total intensity scattering
phase functions, indicating the need for more sophisticated grain models.
