A cosmological sandwiched window for lepton-number breaking scale
Oct 20, 2023
Citations per year
Abstract: (IOP)
A singlet majoron can arise from the seesaw framework as a pseudo-Goldstone boson when the heavy Majorana neutrinos acquire masses via the spontaneous breaking of global U(1) symmetry.The resulting cosmological impacts are usually derived from the effective majoron-neutrino interaction, and the majoron abundance is accumulated through the freeze-in neutrino coalescence. However, a primordial majoron abundance can be predicted in a minimal setup and lead to distinctive cosmological effects. In this work, we consider such a primordial majoron abundance from relativistic freeze-out and calculate the modification to the effective neutrino number N. We demonstrate that the measurements of N will constrain the parameter space from a primordial majoron abundance in an opposite direction to that from neutrino coalescence. When the contributions from both the primordial abundance and the freeze-in production coexist, the U(1)L-breaking scale (seesaw scale) f will be pushed into a “sandwiched window”.Remarkably, for majoron masses below1 MeV and above the eV scale, the future CMB-S4 experiment will completely close such a low-scale seesaw window for f ∈ [1,10] GeV. We highlight that any new light particle with a primordial abundance that couples to Standard Model particles may lead to a similar sandwiched window, and such a general phenomenon deserves careful investigation.Note:
- v2: 32 pages, 6 figures, 1 table, more discussions and references added, version accepted by JCAP
- cosmological neutrinos
- cosmology of theories beyond the SM
- particle physics - cosmology connection
- physics of the early universe
- neutrino: Majorana
- seesaw model
- coalescence
- Goldstone particle
- GeV
- dark matter: freeze-out
References(63)
Figures(4)
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