Rare decays B\to M\nu\bar{\nu} in the TC2 model and the LHT model

In the framework of the topcolor-assisted technicolor ($TC2$) model and the littlest Higgs model with $T$-parity ($LHT$ model), we consider the rare B decays $B\to M\nu \bar{\nu }$ with $M=\pi ,K,\rho ,$ or $K^{\ast }$. We find that the contributions of the $TC2$ model to the branching ratios of these decay processes are larger than those for the $LHT$ model. The experimental upper limits for some branching ratios can give severe constraints on the free parameters of the $TC2$ model.