In October 2015, the duo of scientists Takaaki Kajita (leader of the Super-Kamiokande experiment) and Arthur B. McDonald (leader of the Sudbury Neutrino Observatory – SNO experiment) received the Nobel Prize in Physics for proving that neutrinos have mass through the oscillation of neutrinos , which implies the non-conservation of the lepton number, that is, “glitches” in the standard model.
The neutrino is a very special particle, many scientists affirm that without the neutrino the universe would be totally different.
It belongs to the family of leptons (fermions), it has strange characteristics compared to other fermions, such as the possible fact that the neutrino is its own antiparticle, that is, the neutrino is the same as the antineutrino (this means that the neutrino is a Majorana particle) .
It was also thought for a time that neutrinos traveled faster than light, in September 2011 in a measurement at CERN it was observed that Tau Neutrinos traveled faster than light and consequently reached their destination faster when sent from CERN (on the French-Swiss border) to the Italian laboratory of Gran Sasso for 60 nanoseconds, however in 2012 CERN notified that this was a large measurement error that was due to a bad connection of a fiber optic cable and the wrong synchronization between two stopwatches.
For many years it was thought that the neutrino has a mass of 0, like photons, unfortunately the measurement error in 2011 reaffirmed this idea.
The oscillation of neutrinos is a quantum mechanical phenomenon which describes how a particle in an initial flavor (state) becomes a particle with a different flavor, that is, a neutrino travels through space with a tau flavor (Tau neutrino) and moments later it becomes a neutrino with a muon flavor (Muon neutrino) , this is because each different flavor is a kind of mixture of all the flavors, for this phenomenon to be possible, it is necessary for the particle to have mass.
Neutrinos have already been proven to have mass, so what is their mass? answering this question is a very difficult thing, as far as is known, the mass of the neutrino is about 500,000 times smaller than that of an electron, it is believed that neutrinos do not interact with the Higgs boson (means by which the other fermions acquire mass) , perhaps neutrinos acquire their mass through the Majorana mass term, that is, perhaps they are Majorana particles.
Spectrometer inside.
Within the neutrino experiments there is one called KATRIN, it is focused on measuring the mass of neutrinos through the principle of conservation of energy.
One of the particles to be studied in this research is mainly the electron produced in a beta-type decay (beta particles / beta electrons) , in this type of decay an electron is generated plus an antineutrino or a positron and a neutrino, you may wonder. If you want to measure the mass of a neutrino, why study electrons? This is due to the principle of conservation of energy, » The heavier the emitted neutrino, the less energy the electron has to carry is left over » » Therefore there is a maximum energy that the electron can acquire when the neutrino is emitted » mentioned Boris Kayser, a physicist at Fermilab.
Graphic representation of the apparatus used in the experiment.
KATRIN plans to study the electrons produced in the beta decay of tritium (hydrogen isotope) using a giant tank tuned to a specific voltage that will only allow electrons with a specific energy to pass through.
The giant tank is called MAC Filter – E (Adiabatic Magnetic Collimation with Electrostatic Filter) is a spectrometer in which two superconducting solenoids generate a magnetic field that guides the electrons produced in the decay to the detector, the beam of beta electrons generated that flows through the magnetic field encounters an electrostatic potential generated by cylindrical electrodes, all electrons with enough energy to overcome the electrostatic barrier will be redirected to the detector, the rest will be reflected.
Guido Drexlin, physicist at KIT, Germany (Karlsruhe Institute of Technology) and co-spokesperson at KATRIN said, “If everything works out as planned, I think we will have beautiful results in 2017.”
sources:
- https://www.symmetrymagazine.org/article/weighing-the-lightest-particle
- https://ctp.berkeley.edu/neutrino/neutrino5.html
- https://www.katrin.kit.edu/
- https://www.katrin.kit.edu/79.php
