Non-thermal WIMP Production from Higher Order Moduli Decay
Dr. Amitayus Banik
Chungbuk National University
In a non-standard cosmological scenario, heavy, long-lived particles, called moduli, dominate the energy density prior to Big Bang Nucleosynthesis. Weakly Interacting Massive Particles (WIMPs) may be produced non-thermally from moduli decays, leading to their final relic abundance depending on additional parameters such as the branching ratio of moduli to WIMPs and the modulus mass. Previous works have shown that the correct dark matter (DM) relic density can be obtained, in the case of an overdensity of thermally produced DM, if the moduli, with mass less than $10^7$ GeV, decay to WIMPs with a branching ratio of less than $10^{-4}$. This upper bound could easily be violated once higher order corrections, involving final states with more than two particles, are included. We compute the branching ratios of three- and four-body decays of a modulus into final states involving two DM particles for general couplings, and use them to ascertain bounds on the relevant couplings. As a further application, we treat the case of neutralino DM in the Minimal Supersymmetric Standard Model (MSSM). We find that this requires sparticle masses to be very close to half the modulus mass, in contrast to the idea of weak-scale supersymmetry.
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