  We obtained polarimetric differential imaging of a gas-rich debris disk
around HD 141569A with SPHERE in the H-band to compare the scattering
properties of the innermost ring at 44 au with former observations in total
intensity with the same instrument. In polarimetric imaging, we observed that
the intensity of the ring peaks in the south-east, mostly in the forward
direction, whereas in total intensity imaging, the ring is detected only at the
south. This noticeable characteristic suggests a non-uniform dust density in
the ring. We implemented a density function varying azimuthally along the ring
and generated synthetic images both in polarimetry and in total intensity,
which are then compared to the actual data. We find that the dust density peaks
in the south-west at an azimuthal angle of $220^{\circ} \sim 238^{\circ}$ with
a rather broad width of $61^{\circ} \sim 127^{\circ}$. Although there are still
uncertainties that remain in the determination of the anisotropic scattering
factor, the implementation of an azimuthal density variation to fit the data
proved to be robust. Upon elaborating on the origin of this dust density
distribution, we conclude that it could be the result of a massive collision
when we account for the effect of the high gas mass that is present in the
system on the dynamics of grains. Using the outcome of this modelization, we
further measured the polarized scattering phase function for the observed
scattering angle between 33$^{\circ}$ and 147$^{\circ}$ as well as the spectral
reflectance of the southern part of the ring between 0.98 $\mu$m and 2.1
$\mu$m. We tentatively derived the grain properties by comparing these
quantities with MCFOST models and assuming Mie scattering. Our preliminary
interpretation indicates a mixture of porous sub-micron sized astro-silicate
and carbonaceous grains.
