Heavy neutrino may have influenced the predominance of matter in the Universe — ScienceDaily

Researchers from the University of Southampton and the Indian Institute of Technology Kanpur have proposed a theoretical model according to which an isolated heavy neutrino may have affected why more matter than antimatter remained after the Big Bang. This was reported by ScienceDaily. The findings were published in the journal Physical Review Letters.

According to current understanding, matter and antimatter emerged in nearly equal quantities in the early Universe. During their interaction, particles and antiparticles annihilate, releasing energy. Even a small predominance of matter over antimatter made it possible for the substance from which stars, planets, and living organisms later formed to survive.

Particle's prolonged existence

The team focused on a hypothetical heavier relative of the ordinary neutrino — an isolated heavy neutrino. Because of its extremely weak interaction with other particles, it was generally considered insignificant for the evolution of the cosmos.

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However, the authors' calculations showed that this particle could decay extremely slowly. As the Universe cooled after the Big Bang, it could, the researchers suggest, have existed long enough to temporarily dominate the Universe's energy density. Such a period could have changed the conditions under which the asymmetry between matter and antimatter formed.

Changing the temperature of the early Universe

The authors of the model believe that the heavy neutrino could have shifted the temperature at which electrons and other leptons interacted with their antiparticles involving the Higgs boson of the Standard Model. According to the scientists, this temperature affects the mechanism behind the emergence of the imbalance between matter and antimatter.

Study co-author Sudipta Shaw noted that a change in the nature of the early expansion of the cosmos could have left noticeable traces in primordial gravitational waves. Such signals could potentially make it possible to test whether the proposed particle really influenced the very earliest stages of the Universe's development. For now, this explanation remains theoretical.