  We calculate the back-to-back correlation (BBC) functions of relativistic
boson-antiboson pairs in high energy heavy ion collisions using the Monte Carlo
method. The relativistic effects on the BBC functions of $\phi\,\phi$ and
$K^+K^-$ pairs are investigated. The investigations indicate that the
relativistic effects on the BBC functions of $K^+K^-$ pairs with large momenta
are significant, and the effect is sensitive to the particle freeze-out
temperature.
