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KATRIN Experiment Delivers Most Precise Search Yet for ‘Sterile’ Neutrinos
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Neutrinos are exceptionally challenging to detect, yet they are among the most abundant matter particles in the Universe. According to the Standard Model of particle physics, ther are three known kinds. That picture changed when scientists discovered neutrino oscillations, a phenomenon showing that neutrinos have mass and can switch between types as they move through space. Over the years, several unexplained experimental results have fueled speculation about a fourth variety known as a sterile neutrino, which would interact even more weakly than the others. Confirming its existence would mark a major shift in our understanding of essential physics.
The Hunt for the Elusive Sterile Neutrino
A new study published in Nature details the most precise direct search to date for sterile neutrinos. The research originates from the KATRIN collaboration,meticulously analyzing radioactive decays of tritium to identify subtle indicators of an additional neutrino type. The findings, while not confirming the existence of sterile neutrinos, substantially narrow the parameter space for their potential properties.
How KATRIN Works: A Deep Dive into Tritium Decay
The KATRIN (Karlsruhe Tritium Neutrino) experiment was initially conceived to precisely measure the mass of neutrinos. It achieves this by meticulously tracking the energies of electrons emitted during the beta decay of tritium (3H). During beta decay, a neutron within the tritium nucleus transforms into a proton, emitting an electron and a neutrino. The neutrino carries away some energy, subtly altering the energy distribution of the emitted electrons.
The key to detecting a sterile neutrino lies in looking for a distortion, or “kink,” in this electron energy spectrum. If a sterile neutrino were produced alongside the known neutrino, it would alter the energy balance, creating a measurable deviation. This is because the sterile neutrino would carry away a different amount of energy than the standard neutrinos.
The KATRIN Setup: Precision Engineering on a grand Scale
Located at the Karlsruhe Institute of Technology in Germany, KATRIN is an extraordinary feat of engineering, stretching over 70 meters in length. The experiment’s core components include:
- Windowless Gaseous Tritium Source: This source produces a highly purified beam of tritium gas, minimizing background noise.
- High-Resolution Spectrometer: This is the heart of the experiment, precisely measuring the energies of the emitted electrons using magnetic and electric fields.
- Detector: A sophisticated detector system records the energy and arrival time of each electron.
Since commencing operations in 2019, KATRIN has amassed an unprecedented amount of tritium beta decay data, specifically designed to detect the minute deviations expected from the presence of a sterile neutrino. The experiment’s design prioritizes minimizing systematic uncertainties,ensuring the highest possible precision.
