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Register a new userThe Hubble Tension as a Hint of Leptogenesis and Neutrino Mass Generation
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The majoron, a neutrinophilic pseudo-Goldstone boson conventionally arising in the context of neutrino mass models, can damp neutrino free-streaming and inject additional energy density into neutrinos prior to recombination. The combination of these effects for an eV-scale mass majoron has been shown to ameliorate the outstanding $H_0$ tension, however only if one introduces additional dark radiation at the level of $Delta N_{rm eff} sim 0.5$. We show here that models of low-scale leptogenesis can naturally source this dark radiation by generating a primordial population of majorons from the decays of GeV-scale sterile neutrinos in the early Universe. Using a posterior predictive distribution conditioned on Planck2018+BAO data, we show that the value of $H_0$ observed by the SH$_0$ES collaboration is expected to occur at the level of $sim 10%$ in the primordial majoron cosmology (to be compared with $sim 0.1%$ in the case of $Lambda$CDM). This insight provides an intriguing connection between the neutrino mass mechanism, the baryon asymmetry of the Universe, and the discrepant measurements of $H_0$.
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New interactions of neutrinos can stop them from free streaming even after the weak interaction freeze-out. This results in a phase shift in the cosmic microwave background (CMB) acoustic peaks which can alleviate the Hubble tension. In addition, the perturbations in neutrinos do not decay away on horizon entry and contribute to metric perturbation enhancing the matter power spectrum. We demonstrate that this acoustic phase shift can be achieved using new interactions of standard left-handed neutrinos with dark matter without changing the number of effective relativistic degrees of freedom. Using Planck CMB and the WiggleZ galaxy survey $ (kle 0.12 h {rm Mpc}^{-1} ) $ data, we demonstrate that in this model the Hubble tension reduces to approximately $ 2.1 sigma$. Our model predicts potentially observable modifications of the CMB B-modes and the matter power spectrum that can be observed in future data sets.
In the Minimal Supersymmetric Standard Model (MSSM), the scalar neutrino $tilde{ u}_L$ has odd R parity, yet it has long been eliminated as a dark-matter candidate because it scatters elastically off nuclei through the $Z$ boson, yielding a cross section many orders of magnitude above the experimental limit. We show how it can be reinstated as a dark-matter candidate by splitting the masses of its real and imaginary parts in an extension of the MSSM with scalar triplets. As a result, radiative Majorana neutrino masses are also generated. In addition, decays of the scalar triplets relate the abundance of this asymmetric dark matter to the baryon asymmetry of the Universe through leptogenesis.
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Enrique Fernandez-Martinez
, Mathias Pierre
, Emanuelle Pinsard andn Salvador Rosauro-Alcaraz
2021
We consider the inverse Seesaw scenario for neutrino masses with the approximate Lepton number symmetry broken dynamically by a scalar with Lepton number two. We show that the Majoron associated to the spontaneous symmetry breaking can alleviate the Hubble tension through its contribution to $Delta N_text{eff}$ and late decays to neutrinos. Among the additional fermionic states required for realizing the inverse Seesaw mechanism, sterile neutrinos at the keV-MeV scale can account for all the dark matter component of the Universe if produced via freeze-in from the decays of heavier degrees of freedom.
The recent tension between local and early measurements of the Hubble constant can be explained in a particle physics context. A mechanism is presented where this tension is alleviated due to the presence of a Majoron, arising from the spontaneous breaking of Lepton Number. The lightness of the active neutrinos is consistently explained. Moreover, this mechanism is shown to be embeddable in the Minimal (Lepton) Flavour Violating context, providing a correct description of fermion masses and mixings, and protecting the flavour sector from large deviations from the Standard Model predictions. A QCD axion is also present to solve the Strong CP problem. The Lepton Number and the Peccei-Quinn symmetries naturally arise in the Minimal (Lepton) Flavour Violating setup and their spontaneous breaking is due to the presence of two extra scalar singlets. The Majoron phenomenology is also studied in detail. Decays of the heavy neutrinos and the invisible Higgs decay provide the strongest constraints in the model parameter space.
It has recently been shown that a subdominant hidden sector of atomic dark matter in the early universe can resolve the Hubble tension while maintaining good agreement with most precision cosmological observables. However, such a solution requires a hidden sector whose energy density ratios are the same as in our sector and whose recombination also takes place at redshift $z approx 1100$, which presents an apparent fine tuning. We introduce a realistic model of this scenario that dynamically enforces these coincidences without fine tuning. In our setup, the hidden sector contains an identical copy of Standard Model (SM) fields, but has a smaller Higgs vacuum expectation value (VEV) and a lower temperature. The baryon asymmetries and reheat temperatures in both sectors arise from the decays of an Affleck-Dine scalar field, whose branching ratios automatically ensure that the reheat temperature in each sector is proportional to the corresponding Higgs VEV. The same setup also naturally ensures that the Hydrogen binding energy in each sector is proportional to the corresponding VEV, so the ratios of binding energy to temperature are approximately equal in the two sectors. Furthermore, our scenario predicts a correlation between the SM/hidden temperature ratio and the atomic dark matter abundance and automatically yields values for these quantities that resolve the Hubble tension.
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