%0 Journal Article %T Double-Lepton Polarization Asymmetries in $B_s \rar \phi \ell^+ \ell^-$ Decay in the Fourth-Generation Standard Model %A Zebarjad %A S. M. %A Falahati %A F. %A Mehranfar %A H. %J High Energy Physics - Phenomenology %D 2008 %I %R 10.1103/PhysRevD.79.075006 %X In this paper, we investigate the effects of the fourth generation of quarks on the double-lepton polarization asymmetries in the $B_s \rar \phi \ell^+ \ell^-$ decay. It is shown that these asymmetries in $B_s \rar \phi \ell^+ \ell^-$ decay compared with those of $B \rar K \ell^+ \ell^-$ decay are more sensitive to the fourth-generation parameters. We conclude that an efficient way to establish the existence of the fourth generation of quarks could be the study of these asymmetries in the $B_s \rar \phi \ell^+ \ell^-$ decay. %U http://arxiv.org/abs/0811.2706