Gamma-ray lines may reveal the CP nature of the dark matter particle

Abstract

Determining the fundamental properties of the dark matter is one of the most important open problems in particle physics today. If the dark matter particle has spin zero, one of these properties is its CP nature. That is, whether it is CP-even (scalar), CP-odd (pseudoscalar), or if its interactions violate CP. In this paper, we show that the observation of γ-ray lines arising from the decay of a spin-zero dark matter particle could be used to discriminate among these possibilities. We consider a general setup where dark matter decay is induced by effective operators and demonstrate that, due to gauge invariance, there exists correlations among the branching ratios into gauge boson final states (γγ, γZ, W + W − , ZZ) that depend on the mass and the CP properties of the dark matter. Consequently, the future observation of γ-ray lines may in principle be used to establish the CP nature of the dark matter particle.

Reconstructing non-standard cosmologies with dark matter

“…In general φ decays into both SM radiation and DM particles [90], with a proportion controlled by the parameter b. In fact, b is twice the branching ratio of φ decaying into a couple of DM particles 3 and m φ corresponds to the mass of the state φ. Additionally, 1 − b E/m φ is the fraction of φ energy density that goes into 2 It is necessary to make use of the complementarity between different experiments and different detection techniques [57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73] in order to ameliorate determination of the particle physics parameters and disentangle possible degeneracies. Furthermore, one has to take into account astrophysical uncertainties [74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89] when interpreting the results of the DM searches.…”

“…It is necessary to make use of the complementarity between different experiments and different detection techniques[74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90] in order to ameliorate determination of the particle physics parameters and disentangle possible degeneracies.…”