Asymmetric dark matter from semi-annihilation

Ghosh, Avirup; Ghosh, Deep; Mukhopadhyay, S.

doi:10.1007/jhep08(2020)149

Cited by 15 publications

(23 citation statements)

References 49 publications

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“…The presence of long-range interactions which may lead to bound-state formation reduces the effective number-changing inelastic annihilation rate, and thus reduces the unitarity upper limit compared to the scenario with no bound-state effects [10][11][12]. Furthermore, the presence of a particle anti-particle asymmetry in the DM sector necessarily implies a non-zero equilibrium chemical potential for such DM, thereby increasing the effective number density of the surviving species at freeze-out, and reducing the unitarity upper limits further [11,13]. In particular, as shown in ref.…”

Section: Introductionmentioning

confidence: 99%

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Unitarity limits on thermal dark matter in (non-)standard cosmologies

Bhatia

Mukhopadhyay

2021

J. High Energ. Phys.

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Using the upper bound on the inelastic reaction cross-section implied by S-matrix unitarity, we derive the thermally averaged maximum dark matter (DM) annihilation rate for general k → 2 number-changing reactions, with k ≥ 2, taking place either entirely within the dark sector, or involving standard model fields. This translates to a maximum mass of the particle saturating the observed DM abundance, which, for dominantly s-wave annihilations, is obtained to be around 130 TeV, 1 GeV, 7 MeV and 110 keV, for k = 2, 3, 4 and 5, respectively, in a radiation dominated Universe, for a real or complex scalar DM stabilized by a minimal symmetry. For modified thermal histories in the pre-big bang nucleosynthesis era, with an intermediate period of matter domination, values of reheating temperature higher than $$ \mathcal{O}(200) $$ O 200 GeV for k ≥ 4, $$ \mathcal{O}(1) $$ O 1 TeV for k = 3 and $$ \mathcal{O}(50) $$ O 50 TeV for k = 2 are strongly disfavoured by the combined requirements of unitarity and DM relic abundance, for DM freeze-out before reheating.

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Section: Introductionmentioning

confidence: 99%

“…In particular, as shown in ref. [13], in a purely asymmetric DM scenario, generated by a semi-annihilation process with large CP-violation, the unitarity limit on the DM mass can be as strong as 15 GeV.…”

Section: Introductionmentioning

confidence: 99%

Unitarity limits on thermal dark matter in (non-)standard cosmologies

Bhatia

Mukhopadhyay

2021

J. High Energ. Phys.

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“…In the second example of type B-I, we consider the possibility of producing asymmetric dark matter from semi-annihilation [24], in which the dual role of the CP-conserving processes is demonstrated clearly. In this case, we have the following interaction Lagrangian, consistent with the Z 3 symmetry:…”

Section: Asymmetric Dm From Semi-annihilationmentioning

confidence: 99%

“…The primary source of the CP-violation in a given scenario may also turn out to be scattering processes, with the heavy particle decay processes either sub-dominant or absent [14][15][16]. Such scattering mechanisms have been studied in contexts involving the dark matter (DM) particles as well, in achieving baryogenesis through DM annihilations [17][18][19][20], in relating the baryon and dark matter sector asymmetries [21,22], in realizing the asymmetric DM (ADM) scenario through scatterings [23], and through semiannihilations [24,25].…”

Section: Introductionmentioning

confidence: 99%

Revisiting the role of CP-conserving processes in cosmological particle–antiparticle asymmetries

Ghosh

Mukhopadhyay

2021

Eur. Phys. J. C

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We point out qualitatively different possibilities on the role of CP-conserving processes in generating cosmological particle–antiparticle asymmetries, with illustrative examples from models in leptogenesis and asymmetric dark matter production. In particular, we consider scenarios in which the CP-violating and CP-conserving processes are either both decays or both scatterings, thereby being naturally of comparable rates. This is in contrast to the previously considered CP-conserving processes in models of leptogenesis in different see-saw mechanisms, in which the CP-conserving scatterings typically have lower rates compared to the CP-violating decays, due to a Boltzmann suppression. We further point out that the CP-conserving processes can play a dual role if the asymmetry is generated in the mother sector itself, in contrast to the conventional scenarios in which it is generated in the daughter sector. This is because, the CP-conserving processes initially suppress the asymmetry generation by controlling the out-of-equilibrium number densities of the bath particles, but subsequently modify the ratio of particle antiparticle yields at the present epoch by eliminating the symmetric component of the bath particles through pair-annihilations, leading to a competing effect stemming from the same process at different epochs. We find that the asymmetric yields for relevant particle–antiparticle systems can vary by orders of magnitude depending upon the relative size of the CP-conserving and violating reaction rates.

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“…The primary source of the CP-violation in a given scenario may turn out to be scattering processes, with the heavy particle decay processes either sub-dominant or absent [14][15][16]. Such scattering mechanisms have also been studied in contexts involving the dark matter (DM) particles as well, either in achieving baryogenesis through DM annihilations [17][18][19][20], or in relating the baryon and dark matter sector asymmetries [21,22], or in realizing the asymmetric DM (ADM) scenario [23] through semi-annihilations [24]. Our present study is concerned with the role of CP-conserving annihilation processes in such scenarios in determining the net particle-antiparticle asymmetry, which, to our knowledge, has not been highlighted earlier.…”

Section: Introductionmentioning

confidence: 99%

Revisiting the role of CP-conserving processes in cosmological particle-antiparticle asymmetries

Ghosh,

Mukhopadhyay

2021

Preprint

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The role of CP-violating decay and annihilation processes have been extensively studied in the context of generating cosmological particle-antiparticle asymmetries, both as sources of the asymmetry and its subsequent wash-out. In the scenarios for which the lowest order source of CP-violation is scattering processes, we highlight the role of additional CP-conserving annihilations in indirectly affecting the asymmetry generation. This stems from the strong dependence of the relevant out-of-equilibrium number densities on the rate of CP-conserving reactions. The net asymmetry generated, in turn, is proportional to the out-of-equilibrium number densities and the rate of CP-violation. Such CP-conserving scatterings occur naturally in scenarios of baryogenesis, leptogenesis and asymmetric dark matter production through scattering, as we illustrate through several examples. We find that the asymmetric yields for relevant particle-antiparticle systems can vary by orders of magnitude depending upon the relative size of the CP-conserving and violating reaction rates.

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Asymmetric dark matter from semi-annihilation

Cited by 15 publications

References 49 publications

Unitarity limits on thermal dark matter in (non-)standard cosmologies

Unitarity limits on thermal dark matter in (non-)standard cosmologies

Revisiting the role of CP-conserving processes in cosmological particle–antiparticle asymmetries

Revisiting the role of CP-conserving processes in cosmological particle-antiparticle asymmetries

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