Leakage of power from dipole to higher multipoles due to non-symmetric
  WMAP beam
  A number of studies of WMAP and Planck have highlighted that the power at the
low multipoles in CMB power spectrum are lower than their theoretically
predicted values. Possible angular correlation between the orientations of
these low multipoles have also been claimed. It is important to investigate the
possibility that the power deficiency at low multipoles may not be of
primordial origin and is only an observation artifact coming from the scan
procedure adapted in the WMAP or Planck satellites. Therefore, its always
important to investigate all the observational artifacts that can mimic them.
The CMB dipole which is almost 550 times higher than the quadrupole can leak to
the higher multipoles due to the non-symmetric beam shape of the WMAP. In this
paper a formalism has been developed and simulations are carried out to study
the effect of the non-symmetric beam on this power transfer. It is interesting
to observed that a small but non-negligible amount of power from the dipole can
get transferred to the quadrupole and the higher multipoles due to the
non-symmetric beam. It is shown that in case of WMAP scan strategy the shape of
the quadrupole coming due to this power leakage is very much similar to the
observed quadrupole from WMAP data. Simulations have also been carried out for
Planck scan strategy. It is seen that for Planck scan strategy the power
transfer is not only limited to the quadrupole but also to a few higher low
multipoles. Since the actual beam shapes of Planck are not publicly available
we present results in terms of upper limits on asymmetric beam parameters that
would contaminate of the quadrupole power at the level of $1\mu K$.
