UNIVERSE – Origin of the universe: Why does it have so much matter and so little antimatter?

Lancaster University physicists working on the important international T2K experiment in Japan are approaching the mystery of why there is so much matter in the Universe and so little antimatter.

The Big Bang should have created equal amounts of matter and antimatter in the initial Universe, but the Universe is made of matter. One of the biggest challenges in physics is determining what happened to antimatter, or why we see an asymmetry between matter and antimatter.

The researchers from Tokai to Kamioka (T2K) have revealed in the journal ‘Nature’ that almost half of the possible values ​​of the parameters that determine the asymmetry of matter and antimatter in the Universe have been ruled out.

Dr. Laura Kormos, senior professor of physics at Lancaster University, director of the neutrino physics group and researcher at T2K, explains: “Our data continues to suggest that nature prefers almost the maximum value of asymmetry for this process. It would be like if Mother Nature made these seemingly insignificant particles, difficult to study, be the engine of the existence of the Universe. “

The T2K experiment studies neutrinos, one of the fundamental particles that make up the Universe and one of the least known. However, every second trillion neutrinos from the sun pass through your body. These tiny particles, produced copiously within the sun and other stars, come in three varieties, and can spontaneously change or oscillate from one to the other.

Each type of neutrino has an associated antineutrino. If the type change, or oscillations, are different for neutrinos and antineutrinos, it could help explain the observed domain of matter over antimatter in our Universe, a question that has puzzled scientists for a century.

For most phenomena, the laws of physics provide a symmetrical description of the behavior of matter and antimatter. However, this symmetry must have been broken shortly after the Big Bang to explain the observation of the Universe, which is made up of matter with little antimatter.

A necessary condition is the violation of the so-called load parity symmetry (PC). Until now, there has not been enough observed PC symmetry violation to explain the existence of our Universe.

T2K is looking for a new source of violation of PC symmetry in neutrino oscillations that would manifest as a difference in the probability of oscillation measured for neutrinos and antineutrinos.

The parameter that governs the breaking of the symmetry of matter / antimatter in the neutrino oscillation, called the deltacp phase, can take a value from -180º to 180º. For the first time, T2K has disadvantaged almost half of the possible values ​​at the 99.7% confidence level (3s), and is beginning to reveal a basic property of neutrinos that has not been measured so far.

Dr. Helen O’Keeffe, Senior Professor of Physics at Lancaster University and researcher at T2K adds, “This result will help shape the future stages of T2K and the development of next-generation experiments. It is a very exciting result for many years. working “, highlights.

This is an important step along the way to find out whether neutrinos and antineutrinos behave differently.

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