Description
Chair: Maria Archidiacono
Big Bang nucleosynthesis (BBN) and the cosmic microwave background (CMB) both probe the physics of the early universe. BBN accounts for the cosmic origin of the lightest chemical elements, such as helium-4 and deuterium. Having precisely measured nuclear data and the neutron lifetime as inputs, BBN abundance predictions depend on two cosmological parameters: the cosmic baryon-to-photon ratio...
Neutrino non-standard interactions (NSI) are known to modify the picture of neutrino decoupling from the cosmic plasma. These NSI alter flavour oscillations through matter effects and the annihilation and scattering between neutrinos and electrons and positrons in the thermal plasma. In view of the forthcoming cosmological observations, we perform a precision study of the impact of...
keV-scale gauge-singlet fermions, allowed to mix with the active neutrinos, are elegant dark matter (DM) candidates. They are produced in the early universe via the Dodelson-Widrow mechanism and can be detected as they decay very slowly, emitting X-rays. In the absence of new physics, this hypothesis is virtually ruled out by astrophysical observations. In this talk, I will demonstrate that...
Based on: JCAP 03 (2021) 084 (arXiv: 2012.07519)
We have updated the constraints on flavour universal neutrino self-interactions mediated by a heavy scalar, in the effective 4-fermion interaction limit. We use the relaxation time approximation to modify the collisional neutrino Boltzmann equations, which is known to be very accurate for this particular scenario. Based on the latest CMB data...
We consider heavy sterile neutrinos $\nu_s$ with mass in the range $10~\mathrm{MeV}≤m_s≤m_π∼135~\mathrm{MeV}$, which are thermally produced in the Early Universe, in collisional processes involving active neutrinos, and freezing out after the QCD phase transition. Notably, if these neutrinos decay after the active neutrino decoupling, they generate extra neutrino radiation and contribute to...
Neutrino decay interaction with scalar majorons naturally arises from Standard Model extensions to model neutrino mass generation. The interaction if present during the CMB epoch has the potential to disrupt neutrino free streaming and hence the CMB anisotropy spectra. This has been previously studied as a cosmological constraint on neutrino lifetime. In this work, we model the decay...
An observation of Neutron-antineutron ($n-\bar{n}$) oscillations, would directly imply physics beyond the Standard Model violating baryon number by two units $|\Delta B| = 2$ and hence might provide a close link to the mechanism behind the observed baryon asymmetry of the Universe. In this talk, I will discuss the consequences of such a discovery in the near future, e.g. at the Deep...
In the primordial Universe, neutrino decoupling occurs only slightly before electron-positron annihilations. This leads notably to an increased neutrino energy density compared to the standard instantaneous decoupling approximation, parametrized by the effective number of neutrino species $N_\mathrm{eff}$. A precise calculation of neutrino evolution is needed to assess its consequences on BBN,...
