科学家测定最精确中微子质量上限

Core Insights - The KATRIN experiment has provided the most precise upper limit on the mass of neutrinos, measuring it to be less than 0.45 electron volts (eV), which is less than one-millionth of the mass of an electron [1][2] - This finding constrains the properties of neutrinos, one of the most mysterious fundamental particles in the universe, and pushes the boundaries of physics beyond the Standard Model [1][3] Experiment Details - The KATRIN experiment analyzes the beta decay of tritium to explore neutrino mass, where a tritium nucleus transforms into a helium nucleus, releasing an electron and an electron antineutrino [2] - Between 2019 and 2021, the KATRIN collaboration conducted five measurement campaigns, collecting data over 259 days and measuring the energy of approximately 36 million electrons, achieving a data volume six times greater than previous efforts [2] - The upper limit for the effective mass of electron neutrinos was set at less than 0.45 eV with a confidence level of 90%, marking the strictest laboratory limit on neutrino mass to date [2] Future Prospects - The KATRIN experiment is expected to conclude in 2025 after a total of 1000 days of data collection, with researchers anticipating the ability to estimate the effective electron neutrino mass close to the predicted value of 0.3 eV at a 90% confidence level [2]