nøytrinomassene

Nøytrinomassene refer to the intrinsic mass of neutrinos, fundamental subatomic particles that interact very weakly with matter. For many years, neutrinos were thought to be massless, a prediction consistent with the simplest versions of the Standard Model of particle physics. However, experimental observations of neutrino oscillations, the phenomenon where neutrinos change between their different "flavors" (electron, muon, and tau), provided definitive evidence that neutrinos must possess mass. This discovery was a major breakthrough, requiring extensions or modifications to the Standard Model.

The exact values of the neutrino masses are not yet precisely known, but experiments have established upper limits. Neutrino oscillation experiments measure the differences in the squared masses of the neutrino mass states, denoted as $\Delta m_{12}^2$, $\Delta m_{23}^2$, and $\Delta m_{13}^2$. These mass differences are typically in the order of $10^{-3}$ to $10^{-5}$ eV$^2$. The absolute masses of the neutrinos are more challenging to determine. Experiments like KATRIN (Kaufmann-Lothringen-Zerlegung) aim to measure the electron neutrino mass directly. Current cosmological observations, such as those from the Planck satellite studying the cosmic microwave background, also place constraints on the sum of the neutrino masses, suggesting it is less than approximately 0.12 eV. The existence of non-zero neutrino masses has significant implications for cosmology, particle physics, and our understanding of fundamental forces.