Litmus Test for Cosmic Hemispherical Asymmetry in the Cosmic Microwave
  Background B-mode polarization
  Recent measurements of the temperature field of Cosmic Microwave Background
(CMB) provide tantalising evidence for violation of Statistical Isotropy (SI)
that constitutes a fundamental tenet of contemporary cosmology. CMB space based
missions, WMAP and Planck have observed a $7\%$ departure in the SI temperature
field at large angular scales. However, due to higher cosmic variance at low
multipoles, the significance of this measurement is not expected to improve
from any future CMB temperature measurements. We demonstrate that weak lensing
of the CMB due to scalar perturbations produce a corresponding SI violation in
$B$ modes of CMB polarization at smaller angular scales. Measurability of this
phenomenon depends upon the scales ($l$ range) over which power asymmetry is
present. Power asymmetry which is restricted only to $l<64$ in temperature
field cannot lead to any significant observable effect from this new window.
However, this effect can put an independent bound on the spatial range of
scales of hemispherical asymmetry present in scalar sector.
