If the ‘Big Bang’ created equal amounts of matter and antimatter in the beginning, why today, everything we see from nanobes—the smallest form of life on the Earth—to the largest stellar objects billions of light-years away is made entirely of matter?
As per the prevailing standard model of cosmology, the universe was created in Big Bang out of pure energy. The concept is that the Big Bang produced equal numbers of particles (matter) and antiparticles (antimatter). But what we see around is mostly matter and not antimatter. This constitutes the matter-antimatter asymmetry problem which is one of the greatest mysteries of cosmology.
Antimatter particles in principle are the perfect mirror images of matter, but with the opposite charge. Matter and its twin antimatter exist in equal amounts and if both combine, they annihilate each other, releasing pure energy.
Equivalent number of protons and electrons makes matter neutral and equivalent number of anti-protons and positrons make antimatter neutral. Since matter and antimatter are mostly neutral and weaker nuclear interaction between them keeping them apart, they neither attract nor repel each other and do not annihilate each other. This most profound question in particle physics has puzzled scientists for decades.
Now, an international team of researchers who study neutrino–antineutrino oscillations at T2K (Tokai to Kamioka) explains of the existence of our matter-dominated Universe.
T2K Collaboration, including Imperial College London scientists, has found the strongest evidence yet that neutrinos and antineutrinos behave differently, and therefore may not wipe each other out.
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Dr Patrick Dunne, from the Department of Physics at Imperial, said: "This result brings us closer than ever before to answering the fundamental question of why the matter in our universe exists. If confirmed—at the moment we're over 95 per cent sure—it will have profound implications for physics and should point the way to a better understanding of how our universe evolved."
Previously, scientists have found some differences in behaviour between matter and antimatter versions of subatomic particles called quarks, but the differences observed so far do not seem to be large enough to account for the dominance of matter in the universe.
However, T2K's new result indicates that the differences in the behaviour of neutrinos and antineutrinos appear to be quite large. Neutrinos are fundamental particles but do not interact with normal matter very strongly, such that around 50 trillion neutrinos from the Sun pass through your body every second.
Neutrinos and antineutrinos can come in three 'flavours', known as muon, electron and tau. As they travel, they can 'oscillate'-- changing into a different flavour. The fact that muon neutrinos oscillate into electron neutrinos was first discovered by the T2K experiment in 2013.
"When we started, we knew that seeing signs of differences between neutrinos and antineutrinos in this way was something that could take decades, if they could ever be seen at all, so it is almost like a dream to have our result be celebrated on the cover of Nature this week," said Yoshi Uchida, professor of physics at Imperial College.
