  It has been more than 15 years since the discovery of the top quark. Great
strides have been made in the measurement of the top quark mass and the
properties of it. Most results show consistency with the standard model.
However, using 5 fb$^{-1}$ data, recent measurements of the asymmetry in the
production of top and anti-top quark pair have demonstrated surprisingly large
values at CDF. Using 4 fb$^{-1}$ data, D0 also has similar effect.
