The clustering of galaxies in the SDSS-III Baryon Oscillation
  Spectroscopic Survey: Effect of smoothing of density field on reconstruction
  and anisotropic BAO analysis
  The reconstruction algorithm introduced by \cite{Eis07}, which is widely used
in clustering analysis, is based on the inference of the first order Lagrangian
displacement field from the Gaussian smoothed galaxy density field in redshift
space. The \modif2{smoothing scale} applied to the density field affects the
inferred displacement field that is used to move {the galaxies}, and partially
\modif2{erases} the nonlinear evolution {of the density field}.
  In this article, we explore this crucial step \modif2{in} the reconstruction
algorithm. We study the performance of the reconstruction technique using two
metrics: first, we study the performance using the anisotropic clustering,
extending previous studies focused on isotropic clustering; second, we study
its effect on the displacement field. We find that smoothing has a strong
effect in the quadrupole of the correlation function and affects the accuracy
and precision \modif2{with} which we can measure $D_A (z)$ and $H(z)$. We find
that the optimal smoothing scale to use in the reconstruction algorithm applied
to BOSS-CMASS is between 5-10 $h^{-1}$Mpc. Varying from the "usual"
15$h^{-1}$Mpc to $5 h^{-1}$Mpc \modif2{shows} $\sim$ 0.3\% variations in
$D_A(z)$ and $\sim$ 0.4\% $H(z)$ and uncertainties are also reduced by 40\% and
30\% respectively. We also find that the accuracy of velocity field
reconstruction depends strongly on the smoothing scale used for the density
field. We measure the bias and uncertainties associated with different choices
of smoothing length.
