micrOMEGAs 6.0: N-component dark matter

micrOMEGAs is a numerical code to compute dark matter (DM) observables in generic extensions of the Standard Model (SM) of particle physics. We present a new version of micrOMEGAs that includes a generalization of the Boltzmann equations governing the DM cosmic abundance evolution which can be solved to compute the relic density of N-component DM. The direct and indirect detection rates in such scenarios take into account the relative contribution of each component such that constraints on the combined signal of all DM components can be imposed. The co-scattering mechanism for DM production is also included, whereas the routines used to compute the relic density of feebly interacting particles have been improved in order to take into account the effect of thermal masses of t-channel particles. Finally, the tables for the DM self-annihilation - induced photon spectra have been extended down to DM masses of 110 MeV, and they now include annihilation channels into light mesons. Program summary Program title: micrOMEGAs6.0 CPC Library link to program files: https://doi.org/10.17632/4ck6jf5vxf.3 Licensing provisions: GNU General Public License 3 Programming language: C and Fortran Journal reference of previous version: Comput. Phys. Comm. 231 (2018) 173. Does the new version supersede the previous version?: Yes Reasons for the new version: Previous versions of micrOMEGAs worked within the assumption that DM is composed of one or two components. The new version allows for more components which can be either weekly or feebly interacting. The possibility of co-scattering is also implemented. Summary of revisions: This version includes new routines to compute the abundance of multi-component DM that contains either weakly or feebly interacting dark matter particles in generic extensions of the SM of particle physics. The co-scattering mechanism for DM production is also included. The routines to compute the relic density of feebly interacting particles through the freeze-in mechanism have been improved in order to take into account the effect of thermal masses of t-channel particles. The tables for the photon spectra resulting from pair annihilation have been extended down to dark matter masses of 110 MeV and they now include annihilation channels into light mesons. Nature of problem: DM candidates that satisfy cosmological constraints cover a wide range of masses and interaction strengths. Moreover, the dark sector could contain several stable neutral particles that can all contribute to DM. We provide the first public code to perform a precise computation of the relic density for generic extensions of the SM with more than two component dark matter. Solution method: We solve N Boltzmann equations treating both the cases where the DM components are in thermal equilibrium with the thermal bath in the early Universe, as well as the case where the DM is too feebly interacting to reach equilibrium. We also include decay terms in the Boltzmann equations. All the signals for DM direct and indirect detection take into account the contribution of each component to the total relic density.