KATRIN Experiment & Neutrino Mass — A Scientific Milestone
Relevance : Science & technology
What is KATRIN?
- KATRIN: Karlsruhe Tritium Neutrino Experiment based in Karlsruhe, Germany.
- Objective: To directly measure the mass of the electron neutrino, one of the most elusive particles in nature.
- The core spectrometer was built in Deggendorf (2006) and transported 8,600 km by river and sea due to its 200-tonne weight.
Why Study Neutrinos?
- Neutrinos are neutral, nearly massless, weakly interacting particles.
- They exist in three types (flavours) and exhibit oscillations, proving they have mass — a discovery that won the 2015 Nobel Prize.
- However, oscillations only show mass differences, not absolute mass values.
KATRIN’s Methodology
- Uses molecular tritium decay to detect electrons.
- Focuses on maximum electron energies—which are sensitive to neutrino mass.
- Recorded 36 million electron events across 259 days (2019–2021).
- Set a new upper limit on the sum of all three neutrino masses:
< 0.45 eV (i.e., ≤ 8.8 × 10⁻⁷ of electron mass). - This is twice as precise as previous best results.
Why This Matters
- Standard Model predicts massless neutrinos → proven wrong.
- Implies the need for new physics (possibly unknown forces or particles).
- Opens questions:
- Why are neutrinos so light?
- Are they Majorana particles (their own antiparticles)?
- Investigates if neutrinos participate in neutrinoless double beta decay, which would reveal matter-antimatter asymmetry origins.
Comparison with Other Methods
- Cosmology: Sets tighter theoretical limits based on galaxy formation but involves assumptions about the early universe.
- Double beta decay: Powerful but assumes neutrinos are Majorana from the start.
- KATRIN: Unique because it provides a direct, assumption-free measurement.
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