Neutrino Decay Reconciles Two Worlds ⚡ экспресс
The latest cosmological data (DESI DR2 and the cosmic microwave background) point to an upper limit on the sum of neutrino masses ∑mν ≲ 0.06 eV, which contradicts the lower limits from oscillation experiments. It is shown that neutrino decays into massless particles beyond the Standard Model with lifetimes τν ~ 0.01–1 billion years relax this limit to ∑mν < 0.23 eV (95% C.I.), bringing it into full agreement with oscillation data. For the first time, a cosmological analysis of neutrino decays into lighter neutrinos, consistent with measured mass differences, has been performed. Unlike decays into new physics particles, this scenario only slightly relaxes or even tightens the constraints depending on the mass hierarchy. The results demonstrate that moderately short-lived neutrinos can resolve the key cosmological contradiction without resorting to exotic models.
In the thirties, Pauli realized: without tiny ghost-like particles, the energy of stars doesn't add up. Thus neutrinos were born—intangible wanderers that permeate everything. They must have mass, otherwise they can't transform into one another, but observations of the expansion of the Universe showed their total weight was nearly zero. Meanwhile, laboratory experiments insisted on a larger number.
A new study compares neutrinos to potatoes in a leaky sack. If half the tubers go missing along the way, weighing the remainder will leave you short. It's the same with cosmology: if neutrinos decay into completely invisible particles over a period of ten million to a billion years, today we measure only their surviving fraction. Fresh data from the DESI survey and the cosmic microwave background from the Big Bang allow a mass up to four times higher than previous estimates—enough to settle the dispute.
An unexpected twist: decay into familiar neutrino types yields almost no benefit. The sack still seems full. So nature is hiding something beyond the Standard Model inside it—particles we don't yet know about. That's where the search should go.
🎯 There are almost as many neutrinos in the Universe as photons of the cosmic microwave background—about 330 per cubic centimeter.