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Asimetría de neutrinos que explica por qué hay materia en el Universo

Se superpone la voluntad de los neutrinos sobre los antineutrinos.

The T2K team started seeing signs of a discrepancy in the behavior of neutrinos and antineutrinos in 2016. Their new result, following years of additional data collection and improvements to the data-analysis techniques, rises to a statistical level that physicists regard as official evidence of a physical effect. “The significance of [the effect] increases with the collected data, which is what one expects when the result is correct,” said Werner Rodejohann, a neutrino physicist at the Max Planck Institute for Nuclear Physics in Germany who was not involved in the experiment.


The data implies that neutrinos have a higher probability of oscillating than antineutrinos, a distinction expressed by a quantity called the CP-violating phase. If this phase were zero and neutrinos and antineutrinos behaved the same, the experiment would have detected roughly 68 electron neutrinos and 20 electron antineutrinos. Instead, it found 90 electron neutrinos and only 15 electron antineutrinos — highly skewed results indicating that the CP-violating phase could be as large as theoretically possible.

“We lighted the first candle,” said Sanchez Nieto, “but the big prize” — a definitive discovery of CP violation — “is still to come.”

CP violation among neutrinos supports a theory about how matter came to dominate the universe early on. The theory involves another striking property of neutrinos: They’re all “left-handed,” meaning that a neutrino shooting toward you will always appear to spin clockwise. All antineutrinos, meanwhile, are right-handed; they spin counterclockwise.

Given this, and the fact that neutrinos have an inexplicably tiny amount of mass, experts suspect that neutrinos and antineutrinos once had super heavy counterparts with opposite handedness — right-handed neutrinos and left-handed antineutrinos. These ultra-massive particles would only have been able to form in the hot, energetic early universe, where they would have quickly decayed into lighter particles. But if they decayed asymmetrically, they could easily have produced the matter surplus that makes life and the cosmos possible today.