Associated productions of HZZ and HHZ at linear colliders in large extra dimension model

In this paper we investigate the effects of the large extra dimensions on the two processes e(+)e(-) -> H(0)Z(0)Z(0) and e(+)e(-) -> H(0)H(0)Z(0) at linear colliders in both unpolarized and polarized collision modes. We find that the virtual Kaluza-Klein graviton exchange can significantly enhance the cross section from their standard model expectations for these two processes. The results show that the LED effect on the process e(+)e(-) -> H(0)Z(0)Z(0) allows the observation limits on the effective scale M-S to be probed up to 9.75 TeV and 10.1 TeV in the unpolarized and +-(lambda(e+) = 1/2, lambda(e-) = -1/2) polarized beam collision modes (with Pe+ = 0.6, Pe- = 0.8), respectively. For the process e(+)e(-) -> H(0)H(0)Z(0), these limits on Ms can be probed up to 6.06 TeV and 6.38 TeV in the unpolarized and polarized collision modes separately. We find that the lambda(e+) = 1/2, lambda(e-) = -1/2 polarization collision mode in both process e(+)e(-) -> H(0)Z(0)Z(0) and e(+)e(-) -> H(0)H(0)Z(0) may provide a possibility to improve the sensitivity in probing the LED effects.