  Dissipative hyperbolic systems of \textit{regularity-loss} have been recently
received increasing attention. Usually, extra higher regularity is assumed to
obtain the optimal decay estimates, in comparison with that for the
global-in-time existence of solutions. In this paper, we develop a new
frequency-localization time-decay property, which enables us to overcome the
technical difficulty and improve the minimal decay-regularity for dissipative
systems. As an application, it is shown that the optimal decay rate of
$L^1(\mathbb{R}^3)$-$L^2(\mathbb{R}^3)$ is available for Euler-Maxwell
equations with the critical regularity $s_{c}=5/2$, that is, the extra higher
regularity is not needed.
