Neutralino annihilation processes in the minimal supergravity model

We study all tree-level neutralino annihilation processes concerning energy-dependence at the mSUGRA benchmark point SPS1a using tree-level calculators MadGraph and CompHEP as well as FormCalc. We further investigate the total tree-level neutralino annihilation cross section by scanning over the mSUGRA parameters and identifying the dominant channels in every region. The results for the cross sections are presented in the m1/2-m0 planes for different values of tan(beta) and A0. We identify as well the resonances due to the exchange of the heavy Higgs bosons A and H in the s-channel of many neutralino annihilation processes, where the total cross section increases significantly if these Higgs bosons can be produced close to on-shell. Finally, we provide a few comments on the neutralino annihilation processes at loop-level.