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We consider a vector dark matter (VDM) with a direct coupling with photon. We examine the effect of such an interaction on the CMB polarization to put new constrains on the properties of the DM particles. We show that a partially polarized VDM of the order of temperature fluctuation with a quadrupole distribution leads to a valuable CP for the CMB. In different DM-models the DM-masses range from few eV to a few TeV. We show that the CP angular power spectrum depends on the mass of VDM as C(S)Vlâ1/m6V such that for mV=10eVâ1keV, the CP angular power spectrum is C(S)Vlâ103â10â11nK2. Therefore, the light VDM with masses less than 10eV leads to an unexpected very large CP which can be excluded from the acceptable range of the VDM masses
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