Forgotten particle could answer mystery of why we exist, say physicists
Scientists have unveiled a new theory on the birth of the cosmos, suggesting the early universe was shaped by an ancient particle that has been overlooked for decades.
This article reports on a new theory by physicists at the University of Southampton and the Indian Institute of Technology Kanpur, which posits that an overlooked particle could have played a crucial role in shaping the early universe and why matter ultimately prevailed over antimatter. The key piece of evidence is a rarely considered variant of neutrinos called the "decoupled heavy neutrino."
Unlike other neutrinos, this variant decays extremely slowly. According to Dr. Rishav Roshan from Southampton, this decoupled heavy neutrino remained active for a significant period in the universe's history, after the Big Bang, which allowed it to temporarily dominate the universe's energy density. This dominance could have caused a period where matter was the dominant force, effectively resolving the long-standing question of why matter and not antimatter predominates.
The study, published in Physical Review Letters, suggests that the decoupled neutrino influenced the temperature at which fundamental particles like electrons interacted with their antiparticles. This temperature shift, mediated by the Standard Model Higgs boson, acted like a switch, altering the conditions that built up the matter-antimatter asymmetry.
As a result, the cosmological expansion that followed the Big Bang was altered, leaving unique imprints on primordial gravitational waves. Detecting these imprints could provide new insights into the early universe's evolution.
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