  The momentum distribution and particle correlation due to the mass difference
were studied both in the case of the conventional expectation value and in the
case of $q$-expectation value, when the momentum distribution is described by a
Tsallis distribution with the entropic parameter $q \ge 1$. The magnitude of
the momentum distribution for hard modes increases as $q$ increases, and the
$q$-dependence of the momentum distribution is quite weak for soft modes. The
correlation at $q>1$ is larger than that at $q=1$ for soft modes, while the
correlation at $q>1$ is smaller than that at $q=1$ for hard modes. The
$q$-dependence of these quantities in the case of $q$-expectation value is
weaker than that in the case of the conventional expectation value,
respectively.
