It’s called the T2K Experiment, which stands for Tokai to Kamioka, and involves shooting a beam of neutrinos (underground) from the Japan Proton Accelerator Research Complex, or J-PARC, on the country’s east coast to a “pure water” particle detector near Japan’s west coast. The total distance traveled by these mysterious quantum particles is about 185 miles (295 km).
And so far, the data coming in from T2K reveals some pretty curious behavior on the part of neutrinos: they change ‘flavor’…And, in so doing, they just might provide the key clue for solving what’s known as matter-antimatter asymmetry, or ‘charge-parity (CP) violation’.
According to cosmology theory, at the moment of the Big Bang, matter and antimatter were created in equal proportions. This is expected because, according to theory, every matter particle must have its antimatter counterpart, and the laws of physics should be the same for either type of particle. This is known as CP symmetry in which particle charge (C) and/or its mirror image (P, for parity) may be swapped without any change in physical behavior.
An antimatter particle looks just like the matter version, but has an opposite charge (positive/negative) and parity (left/right mirror image) and is viewed, mathematically, as traveling “backwards in time”.
Problem is: when matter and antimatter meet, they annihilate each other.
So then, why is our universe filled with matter and virtually no antimatter — and why is there a matter universe at all, since it should have annihilated itself immediately as both matter and antimatter emerged simultaneously from the ‘quantum field’? That is the puzzle that physicists have long-labored to solve.
Neutrinos are fundamental, “building block” particles that travel at the speed of light. Neutrinos can pass through ordinary matter unperturbed (making them hard to detect); there are billions of neutrinos passing through the Earth, and your body, at this very moment. Neutrinos are formed from a type of radioactive decay and in nuclear reactions. They are electrically neutral (the name means “little neutral one”) and also come in three different “flavors”, or forms: the muon, electron, and tau neutrinos. And, you guessed it — each flavor has its corresponding antineutrino.
What physicists discovered from the T2K experiments is that, in the course of their travels, some neutrinos change their flavor — changing from muon to electron neutrinos. Remember, when this happens, the corresponding antineutrinos should also change. Neutrino flavor changes — called oscillations — have been observed before (the first being reported in the the first ‘Super-Kamiokande’ experiment), but this T2K result represents a “new type of neutrino oscillation” that has never been observed/measured before.
These tests allow physicists to study a fundamental parameter of neutrino activity called theta-13 (the neutrino “mixing angle”) and future measurements of this parameter — if not too small — may indicate what happened to all that putative antimatter that emerged at the start of the Universe.
So, if these fundamental particles can spontaneously change their flavor (which also determines their physical properties), then what about the antineutrinos? Can fluctuations in antineutrinos result in preventing the complete, mutual annihilation of the two, resulting in the matter-dominated universe that we observe around us? The answer to this parallel question may help solve one of Physics’ longest-standing mysteries.
A previous, theoretical explanation (Davoudiasl, et al) for this matter-antimatter asymmetry (or baryonic asymmetry) postulated a “hidden sector” (or dimension) of particles and ‘fields’ that couple to dark matter and neutrons, and that act as reservoirs or conduits for the missing antimatter particles, thus restoring (total) CP Symmetry.
The T2K experiment is one of the largest particle physics collaborations ever conducted and involves some 500 scientists from 12 nations. Additionally, ten U.S. universities participated in the project — all sponsored bu the US Dept. of Energy. The preliminary findings were submitted to Physical Review Letters and announced at a press conference June 15 in Japan.
To learn more about the T2K Experiment, visit the T2K website.
Watch a video of the T2K ‘basket’ detector’s magnets closing:
And here’s a video animation showing a sample of neutrino events collected by the near detector (of the T2K experiment on February 1, 2010:
Some source material for this post came from the this Sciencecodex.com article: Why matter trumped antimatter – muon neutrinos can change ‘flavors’ to electron?
Top Photo: (T2K “basket detector” with magnets open); The T2K website (public)