
Aristizabal Sierra, D., Tortola, M., Valle, J. W. F., & Vicente, A. (2014). Leptogenesis with a dynamical seesaw scale. J. Cosmol. Astropart. Phys., 07(7), 052–20pp.
Abstract: In the simplest typeI seesaw leptogenesis scenario righthanded neutrino annihilation processes are absent. However, in the presence of new interactions these processes are possible and can affect the resulting B – L asymmetry in an important way. A prominent example is provided by models with spontaneous lepton number violation, where the existence of new dynamical degrees of freedom can play a crucial role. In this context, we provide a modelindependent discussion of the effects of righthanded neutrino annihilations. We show that in the weak washout regime, as long as the scattering processes remain slow compared with the Hubble expansion rate throughout the relevant temperature range, the efficiency can be largely enhanced, reaching in some cases maximal values. Moreover, the B – L asymmetry yield turns out to be independent upon initial conditions, in contrast to the “standard” case. On the other hand, when the annihilation processes are fast, the righthanded neutrino distribution tends to a thermal one down to low temperatures, implying a drastic suppression of the efficiency which in some cases can render the B – L generation mechanism inoperative.



Barenboim, G., & Park, W. I. (2017). A full picture of large lepton number asymmetries of the Universe. J. Cosmol. Astropart. Phys., 04(4), 048–10pp.
Abstract: A large lepton number asymmetry of O(0.11) at present Universe might not only be allowed but also necessary for consistency among cosmological data. We show that, if a sizeable lepton number asymmetry were produced before the electroweak phase transition, the requirement for not producing too much baryon number asymmetry through sphalerons processes, forces the high scale lepton number asymmetry to be larger than about 30. Therefore a mild entropy release causing O(10100) suppression of preexisting particle density should take place, when the background temperature of the Universe is around T = O(10(2) 10(2)) GeV for a large but experimentally consistent asymmetry to be present today. We also show that such a mild entropy production can be obtained by the latetime decays of the saxion, constraining the parameters of the PecceiQuinn sector such as the mass and the vacuum expectation value of the saxion field to be m(phi) greater than or similar to O(10) TeV and phi(0) greater than or similar to O(10(14)) GeV, respectively.



Bernal, N., Colucci, S., JosseMichaux, F. X., Racker, J., & Ubaldi, L. (2013). On baryogenesis from dark matter annihilation. J. Cosmol. Astropart. Phys., 10(10), 035–30pp.
Abstract: We study in detail the conditions to generate the baryon asymmetry of the universe from the annihilation of dark matter. This scenario requires a low energy mechanism for thermal baryogenesis, hence we first discuss some of these mechanisms together with the specific constraints due to the connection with the dark matter sector. Then we show that, contrary to what stated in previous studies, it is possible to generate the cosmological asymmetry without adding a light sterile dark sector, both in models with violation and with conservation of B – L. In addition, one of the models we propose yields some connection to neutrino masses.



Bhattacharya, S., Mondal, N., Roshan, R., & Vatsyayan, D. (2024). Leptogenesis, dark matter and gravitational waves from discrete symmetry breaking. J. Cosmol. Astropart. Phys., 06(6), 029–25pp.
Abstract: We analyse a model that connects the neutrino sector and the dark sector of the universe via a mediator 41., stabilised by a discrete Z4 symmetry that breaks to a remnant Z2 upon 41. acquiring a non zero vacuum expectation value (v phi). The model accounts for the observed baryon asymmetry of the universe via additional contributions to the canonical Type I leptogenesis. The Z4 symmetry breaking scale (v phi) in the model not only establishes a connection between the neutrino sector and the dark sector, but could also lead to gravitational wave signals that are within the reach of current and future experimental sensitivities.



Boubekeur, L., Choi, K. Y., Ruiz de Austri, R., & Vives, O. (2010). The degenerate gravitino scenario. J. Cosmol. Astropart. Phys., 04(4), 005–26pp.
Abstract: In this work, we explore the “degenerate gravitino” scenario where the mass difference between the gravitino and the lightest MSSM particle is much smaller than the gravitino mass itself. In this case, the energy released in the decay of the next to lightest sypersymmetric particle (NLSP) is reduced. Consequently the cosmological and astrophysical constraints on the gravitino abundance, and hence on the reheating temperature, become softer than in the usual case. On the other hand, such small mass splittings generically imply a much longer lifetime for the NLSP. We find that, in the constrained MSSM (CMSSM), for neutralino LSP or NLSP, reheating temperatures compatible with thermal leptogenesis are reached for small splittings of order 10(2) GeV. While for stau NLSP, temperatures of TRH similar or equal to 4 x 10(9) GeV can be obtained even for splittings of order of tens of GeVs. This “degenerate gravitino” scenario offers a possible way out to the gravitino problem for thermal leptogenesis in supersymmetric theories.



Di Bari, P., Ludl, P. O., & PalomaresRuiz, S. (2016). Unifying leptogenesis, dark matter and highenergy neutrinos with righthanded neutrino mixing via Higgs portal. J. Cosmol. Astropart. Phys., 11(11), 044–41pp.
Abstract: We revisit a model in which neutrino masses and mixing are described by a two righthanded (RH) neutrino seesaw scenario, implying a strictly hierarchical light neutrino spectrum. A third decoupled RH neutrino, NDM with mass MDM, plays the role of cold dark matter (DM) and is produced by the mixing with a source RH neutrino, Ns with mass MS, induced by Higgs portal interactions. The same interactions are also responsible for NDM decays. We discuss in detail the constraints coming from DM abundance and stability conditions showing that in the hierarchical case, for MDM >> MS, there is an allowed window on MDM values necessarily implying a contribution, from DM decays, to the highenergy neutrino flux recently detected by IceCube. We also show how the model can explain the matterantimatter asymmetry of the Universe via leptogenesis in the quasidegenerate limit. In this case, the DM mass should be within the range 300 GeV less than or similar to MS < MDM < 10PeV. We discuss the specific properties of this highenergy neutrino flux and show the predicted event spectrum for two exemplary cases. Although DM decays, with a relatively hard spectrum, cannot account for all the IceCube highenergy data, we illustrate how this extra source of highenergy neutrinos could reasonably explain some potential features in the observed spectrum. In this way, this represents a unified scenario for leptogenesis and DM that could be tested during the next years with more highenergy neutrino events.



Drewes, M., Georis, Y., Hagedorn, C., & Klaric, J. (2022). Lowscale leptogenesis with flavour and CP symmetries. J. High Energy Phys., 12(12), 044–113pp.
Abstract: We consider a typeI seesaw framework endowed with a flavour symmetry, belonging to the series of nonabelian groups increment (3 n(2)) and increment (6 n(2)), and a CP symmetry. Breaking these symmetries in a nontrivial way results in the righthanded neutrinos being degenerate in mass up to possible (further symmetrybreaking) splittings kappa and lambda, while the neutrino Yukawa coupling matrix encodes the entire flavour structure in the neutrino sector. For a fixed combination of flavour and CP symmetry and residual groups, this matrix contains five real free parameters. Four of them are determined by the light neutrino mass spectrum and by accommodating experimental data on lepton mixing well, while the angle theta(R) is related to righthanded neutrinos. We scrutinise for all four lepton mixing patterns, grouped into Case 1) through Case 3 b.1), the potential to generate the baryon asymmetry of the Universe through lowscale leptogenesis numerically and analytically. The main results are: a) the possible correlation of the baryon asymmetry and the Majorana phases, encoded in the PontecorvoMakiNakagawaSakata mixing matrix, in certain instances; b) the possibility to generate the correct amount of baryon asymmetry for vanishing splittings kappa and lambda among the righthanded neutrinos as well as for large kappa, depending on the case and the specific choice of group theory parameters; c) the chance to produce sufficient baryon asymmetry for large activesterile mixing angles, enabling direct experimental tests at current and future facilities, if theta(R) is close to a special value, potentially protected by an enhanced residual symmetry. We elucidate these results with representative examples of flavour and CP symmetries, which all lead to a good agreement with the measured values of the lepton mixing angles and, possibly, the current indication of the CP phase delta. We identify the CPviolating combinations relevant for lowscale leptogenesis, and show that the parametric dependence of the baryon asymmetry found in the numerical study can be understood well with their help.



Felipe, R. G., Joaquim, F. R., & Serodio, H. (2013). Flavored CP asymmetries for type II seesaw leptogenesis. Int. J. Mod. Phys. A, 28(31), 1350165–13pp.
Abstract: A novel contribution to the leptonic CP asymmetries in type II seesaw leptogenesis scenarios is obtained for the cases in which flavor effects are relevant for the dynamics of leptogenesis. In the socalled flavored leptogenesis regime, the interference between the treelevel amplitude of the scalar triplet decaying into two leptons and the oneloop wave function correction with leptons in the loop, leads to a new nonvanishing CP asymmetry contribution. The latter conserves total lepton number but violates lepton flavor. Cases in which this novel contribution may be dominant in the generation of the baryon asymmetry are briefly discussed.



Hernandez, P., LopezPavon, J., Rius, N., & Sandner, S. (2022). Bounds on righthanded neutrino parameters from observable leptogenesis. J. High Energy Phys., 12(12), 012–58pp.
Abstract: We revisit the generation of a matterantimatter asymmetry in the minimal extension of the Standard Model with two singlet heavy neutral leptons (HNL) that can explain neutrino masses. We derive an accurate analytical approximation to the solution of the complete linearized set of kinetic equations, which exposes the nontrivial parameter dependencies in the form of parameterizationindependent CP invariants. The identification of various washout regimes relevant in different regions of parameter space sheds light on the relevance of the mass corrections in the interaction rates and clarifies the correlations of baryogenesis with other observables. In particular, by requiring that the measured baryon asymmetry is reproduced, we derive robust upper or lower bounds on the HNL mixings depending on their masses, and constraints on their flavour structure, as well as on the CPviolating phases of the PMNS mixing matrix, and the amplitude of neutrinoless doublebeta decay. We also find certain correlations between low and high scale CP phases. Especially emphasizing the testable part of the parameter space we demonstrate that our findings are in very good agreement with numerical results. The methods developed in this work can help in exploring more complex scenarios.



Racker, J. (2014). Mass bounds for baryogenesis from particle decays and the inert doublet model. J. Cosmol. Astropart. Phys., 03(3), 025–23pp.
Abstract: In models for thermal baryogenesis from particle decays, the mass of the decaying particle is typically many orders of magnitude above the TeV scale. We will discuss different ways to lower the energy scale of baryogenesis and present the corresponding lower bounds on the particle's mass. This is done specifically for the inert doublet model with heavy Majorana neutrinos and then we indicate how to extrapolate the results to other scenarios. We also revisit the question of whether or not dark matter, neutrino masses, and the cosmic baryon asymmetry can be explained simultaneously at low energies in the inert doublet model.

