Thermal dark matter co-annihilating with a strongly interacting scalar

Abstract

Recently many investigations have considered Majorana dark matter coannihilating with bound states formed by a strongly interacting scalar field. However only the gluon radiation contribution to bound state formation and dissociation, which at high temperatures is subleading to soft 2 → 2 scatterings, has been included. Making use of a non-relativistic effective theory framework and solving a plasma-modified Schrödinger equation, we address the effect of soft 2 → 2 scatterings as well as the thermal dissociation of bound states. We argue that the mass splitting between the Majorana and scalar field has in general both a lower and an upper bound, and that the dark matter mass scale can be pushed at least up to 5 . . . 6 TeV.

Non-relativistic susceptibility and a dark matter application

“…5, at low temperatures the coupling α is evaluated at the MS scale ∼ e −γ E /a, and at high temperatures we use a thermal coupling; the crossover takes place at z ≈ 250...600 for M = 1...500 TeV. ThisS 3 attaches rather smoothly to the more elaborate results described in ref [25]…”

“…where ∆E = α 2 M/4, and we have for convenience defined a ∆M T -independentp 2 . The corresponding approximation for the attractive Sommerfeld factor reads [25] S 3 ≈ 4π M T and after including a thermally averaged Sommerfeld factor ("withS 3 ") and a susceptibility ("withS 3 andp 2 "). The symbols y, λ 3 , h refer to couplings defined in ref.…”

“…The symbols y, λ 3 , h refer to couplings defined in ref. [25], whose precise values have little impact on the general pattern. This plot assumes that kinetic/ionization equilibrium is maintained in the dark sector.…”

“…(6.3) at z > ∼ 200. The repulsive Sommerfeld factors S 4,5 [25], which are not important at late times, are frozen to their values at z ≃ 200. Numerical values of T 3p 2 andS 3 are shown in fig.…”

Scalar dark matter coannihilating with a coloured fermion

“…The latter effect has been only recently addressed in DM models. Various different formalisms are in use in the literature [12,[16][17][18][19][20]. The main common outcome of these studies is that larger DM masses are compatible with the relic density because a larger cross section is found.…”