Dynamics of the pseudo-FIMP in presence of a thermal Dark Matter

Abstract

We demonstrate that in a two component dark matter (DM) set up, when DM${}_1$ is equilibrated with the thermal bath, the other DM${}_2$, in spite of having feeble or negligible interaction with the SM particles, can be brought to equilibrium just by having sizeable interaction with DM${}_1$. We propose that such DM candidates (DM${}_2$) should be classified into a category called pseudo-FIMP (pFIMP) having unique freeze-out characteristics which depend on the thermal DM partner. The draft elaborates upon the pFIMP properties from a generic coupled Boltzmann Equations (cBEQ) in a model independent way, followed by a concrete model illustration.

Comments: 12 pages, 10 figures; version published in Phys.Rev.D (Letter)