11th June 2025 (9 Topics)
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KATRIN Experiment
Context
The Karlsruhe Tritium Neutrino Experiment (KATRIN) in Germany has recently announced a new upper limit on the combined mass of all three types of neutrinos, improving the previous limit by a factor of two. The new constraint, based on 259 days of data between March 2019 and June 2021, sets the sum of neutrino masses at less than 0.8 eV or 8.8 × 10?? times the mass of an electron.
What is KATRIN?
- The Karlsruhe Tritium Neutrino Experiment (KATRIN) is a precision experiment designed to measure the mass of neutrinos by examining the beta decay of tritium. It uses a large spectrometer to detect tiny changes in the energy spectrum of emitted electrons.
Why Tritium Decay?
- Tritium (³H) undergoes beta decay into helium-3, releasing an electron and an electron antineutrino. The energy distribution of the emitted electron helps infer the mass of the neutrino.
Why Measuring Neutrino Mass is Hard?
- Neutrinos interact extremely weakly with matter and have an extremely small mass (nearly zero). The Standard Model originally predicted them to be massless, so their mass points toward new physics beyond the Standard Model.
Significance of New Limit:
- KATRIN set a new upper limit on the sum of the three neutrino masses at 0.8 eV, the most robust limit not dependent on cosmological assumptions or unverified decay processes (like neutrinoless double-beta decay).
Complementary Efforts:
- Cosmological experiments (like Planck) estimate neutrino mass based on galaxy structure, setting even tighter limits (around 12 eV), but those are model-dependent. KATRIN is model-independent.
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