Relic Density Computation in MadDM

Compute the relic density and thermally averaged cross section of a dark matter candidate.

Overview

The code is able to handle the full effects of co-annihilations and resonant annihilation in a generic model. In models which contain more than one dark matter particle, MadDM can solve either the full set of coupled density evolution equations or a single equation involving effective thermally averaged cross sections. The former gives MadDM the ability to calculate relic density in models which allow for dark matter conversions.

Relic Density of a Simplified DM Model

In this example, we compute the relic density and the thermally averaged cross section at freeze-out of a vector mediated fermionic dark matter candidate.

First, import the model and define the dark matter candidate. We use the DMsimp_s_spin1 model. Generally, for DMsimp models, you can choose between Xr (real scalar DM), Xc (complex scalar DM) and Xd (Dirac spinor DM).

MadDM> import model DMsimp_s_spin1
MadDM> define darkmatter xd

Then, generate the relic density processes with:

MadDM> generate relic_density

Next, create the process folder. In this case, we call it RD_spin1, but you can choose any name you like. Then launch the process:

MadDM> output RD_spin1
MadDM> launch RD_spin1

Select to run the relic module (but it should be already ON) by entering:

MadDM> relic = ON

You can set the model parameters in the param_card.dat by pressing 6, or by editing the file directly in the process folder (in this case DD_NR_spin0/Cards/param_card.dat).

You can set the MadDM parameters (such as the halo parameters, recoil energy range and much more) in the maddm_card.dat by pressing 7, or by editing the file directly in the process folder (in this case DD_NR_spin0/Cards/maddm_card.dat).

Once you are all set, you can run the process by pressing Enter.

This module will first evaluate the relic density, flagging it as either underabundant or overabundant.

If also shows the freeze-out parameter and the thermally averaged cross section at freeze-out.

The parameter xsi is the relic density rescaling factor.

Finally, MadDM shows the contributions of each annihilation channel to the total relic density.

****** Relic Density
OMEGA IS 10.139932
INFO: Relic Density       = 1.01e+01       OVERABUNDANT
INFO: x_f                 = 1.40e+01
INFO: sigmav(xf)          = 8.50e-29 cm^3 s^-1
INFO: xsi                 = 1.00e+00
INFO:
INFO: Channels contributions:
INFO: xdxdx_ddx           : 20.08 %
INFO: xdxdx_uux           : 20.08 %
INFO: xdxdx_ssx           : 20.08 %
INFO: xdxdx_ccx           : 20.08 %
INFO: xdxdx_bbx           : 19.69 %
INFO: No contribution from processes: xdxdx_y1y1, xdxdx_emep, xdxdx_mummup, xdxdx_vevex, xdxdx_vmvmx, xdxdx_vtvtx, xdxdx_dbx, xdxdx_utx, xdxdx_bdx, xdxdx_tux, xdxdx_ttx, xdxdx_zh, xdxdx_tamtap
INFO:
INFO: Results written in:  /Users/yourname/yourprocessfolder/RD_spin1/output/run_01/MadDM_results.txt
quit

Exiting MadDM

MadDM> quit