🎭 This strange quantum metamorphosis could explain the dominance of matter over antimatter

A recent study published in Nature combines data from two major experiments - NOvA in the United States and T2K in Japan - to observe with unprecedented precision how neutrinos, particles capable of passing through almost all matter as if it didn't exist, change identity during their journey.

These elementary particles exist in three distinct forms: electron, muon, and tau, and their ability to transform from one type to another deeply intrigues physicists. This metamorphosis, called neutrino oscillation, could hold the key to understanding why our Universe is primarily composed of matter rather than antimatter.


The NOvA experiment propels a beam of muon neutrinos through the ground from Illinois to Minnesota over a distance of 800 kilometers (about 500 miles), while T2K sends its neutrinos through Japanese mountains. These different paths allow scientists to study oscillations under various energy conditions and distances. Zoya Vallari, a physicist at Ohio State University, compares this phenomenon to a chocolate ice cream that would continuously transform into mint then vanilla flavor while walking down the street.

Researchers are particularly seeking to determine whether neutrinos and their antiparticles behave differently, a phenomenon called Charge-Parity symmetry violation. Confirmation of this asymmetry would explain why matter dominated antimatter after the Big Bang. Although current results don't yet provide a definitive answer, they represent a significant advance in our understanding of these fundamental particles.

This collaboration between normally competing teams demonstrates the importance of the stakes. John Beacom, a professor at Ohio State, emphasizes that the complexity of this work requires the participation of hundreds of researchers. The combined data from both experiments offer a more complete perspective than a single isolated study, paving the way for the next generation of neutrino detectors currently under development.

Physicists will continue to refine their analyses with new data, gradually building the foundations for future discoveries that could revolutionize our vision of the Universe. As Zoya Vallari reminds us, beyond technological applications, it's human curiosity to understand our origins and our place in the cosmos that motivates this ambitious research.

Neutrino oscillation

Neutrino oscillation refers to the astonishing ability of these particles to change type during their movement. This quantum phenomenon implies that neutrinos don't possess a clearly defined mass but exist in a state of superposition of their three "flavors."

The discovery of this property earned the Nobel Prize in Physics in 2015 and forced scientists to revise the Standard Model of particle physics. Oscillations occur because the flavor states and mass states of neutrinos don't perfectly coincide.

This mechanism explains why we detect fewer neutrinos emitted by the Sun than expected - some transformed into undetectable types during their journey from the Sun. The precise study of oscillation parameters allows measurement of the mass differences between the three types of neutrinos.

Detailed understanding of these oscillations opens the way to new physics beyond the current Standard Model, potentially revealing fundamental symmetries of the Universe.

CP violation in neutrinos

Charge-Parity symmetry violation (CP violation) represents one of the most important quests in modern physics. This phenomenon occurs when physical laws treat particles and their antiparticles differently.

In neutrinos, CP violation would manifest if oscillations of neutrinos and antineutrinos followed different probabilities. This asymmetry could explain the matter-antimatter imbalance observed in the Universe.

The Big Bang should have produced equal amounts of matter and antimatter, which should have annihilated each other. The existence of our matter-made Universe suggests that a mechanism eliminated antimatter, and neutrinos could be the main actors.

The definitive detection of CP violation in neutrinos will require even more precise experiments, such as those planned with future next-generation detectors currently under construction in several countries.