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.
Heavy Majorana neutrinos enter in many scenarios of physics beyond the
Standard Model: in the original seesaw mechanism they provide a natural
explanation for the small masses of the Standard Model neutrinos and in the
simplest leptogenesis framework they are at the origin of the baryonic matter
of the universe. In this paper, we develop an effective field theory for
non-relativistic Majorana particles, which is analogous to the heavy-quark
effective theory. Then, we apply it to the case of a heavy Majorana neutrino
decaying in a hot and dense plasma of Standard Model particles, whose
temperature is much smaller than the mass of the Majorana neutrino but still
much larger than the electroweak scale. The neutrino width gets
zero-temperature contributions that can be computed from in-vacuum matrix
elements, and thermal corrections. Only the latter will be addressed. Symmetry
and power counting arguments made manifest by the effective field theory
restrict the form of the thermal corrections and simplify their calculation.
The final result agrees with recent determinations obtained with different
methods. The effective field theory presented here is suitable to be used for a
variety of different models involving non-relativistic Majorana fermions.Comment: Published version. 25 pages, 7 figures, references adde
We apply a formalism accounting for thermal effects (such as modified
Sommerfeld effect; Salpeter correction; decohering scatterings; dissociation of
bound states), to one of the simplest WIMP-like dark matter models, associated
with an "inert" Higgs doublet. A broad temperature range T ~ M/20...M/10^4 is
considered, stressing the importance and less-understood nature of late
annihilation stages. Even though only weak interactions play a role, we find
that resummed real and virtual corrections increase the tree-level overclosure
bound by 1...18%, depending on quartic couplings and mass splittings.Comment: 29 pages. v2: clarifications added, published versio
In many realizations of leptogenesis, heavy right-handed neutrinos play the main role in the generation of an imbalance between matter and antimatter in the early Universe. Hence, it is relevant to address quantitatively their dynamics in a hot and dense environment by taking into account the various thermal aspects of the problem at hand. The strong washout regime offers an interesting framework to carry out calculations systematically and reduce theoretical uncertainties. Indeed, any matter-antimatter asymmetry generated when the temperature of the hot plasma T exceeds the right-handed neutrino mass scale M is efficiently erased, and one can focus on the temperature window T M . We review recent progresses in the thermal field theoretic derivation of the key ingredients for the leptogenesis mechanism: the right-handed neutrino production rate, the CP asymmetry in the heavy-neutrino decays and the washout rates. The derivation of evolution equations for the heavy-neutrino and lepton-asymmetry number densities, their rigorous formulation and applicability are also discussed.
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