"Fermilab's MINOS experiment, designed to study oscillations in neutrino identity, has turned up evidence that the mass differences among neutrinos and anti-neutrinos may be different, indicating something is breaking the mirror-like symmetry between the two."
Although the Standard Model has been around for decades, it was never complete. Almost so, but there is an elusive particle which has been predicted, the Higgs boson, which if discovered, could tie the proverbial particle ribbon and present quantum mechanics with one of the most solid theories in all physics.
Click image for larger chart.
Unfortunately, not all the particles are willing to cooperate. Researchers at Fermi Lab in Batavia, Illinois have uncovered a break in symmetry while studying the very shy neutrino. In particle physics, each particle has its anti-particle (an identical particle in mass except that it possesses opposite charge). When a particle and its anti-particle meet, they annihilate one another, releasing pure energy. For some so-far inexplicable reason, there are more unmated particles left over than expected which is good for us, as these left over particles are the source of everything we know and see. In the Standard Model, every particle has its own behavior - properties - which causes it to follow particular paths, or patterns, when excited. That's how physicists can "see' them- by the specific trails they leave when smashed together.
The Standard model can be demonstrated with a simple Chart but don't let its apparent simplicity fool you. Everything that garnered its position arrived there via hair-pulling computations. Particles are either discovered or predicted by theorists and then hopefully discovered in subsequent experiments. Fermi Lab is a particle accelerator like the Large Hadron Collider in Cern, Switzerland, but it's smaller. Not so small, though, that it hasn't produced some fantastic science.
Let's backtrack a moment. To understand the magnitude of this finding, you'll need a basic grasp of the Standard Model (SM). For a superb graphic explanation, we recommend The Particle Adventure's four part section called "The Standard Model" (easy to remember!). Beginning with "Eternal Questions", you'll be taken through the current state of Particle physics' Standard Model and will leave with a wonderful grasp of exactly what's going on. Simplistically, the SM is the list of all the fundamental particles, and how they interact. A fundamental particle is one which is not composed of smaller parts, but is itself the smallest part (that we now know; should String Theory turn out to be fact, then each of these particles is composed of even tinier sets of properties which are called "strings' and the differences in them are due to the way in which each string is vibrating. But that's not needed here).
There are 6 quarks, 6 leptons, 4 forces. That's it!
Quarks are the small particles of matter which make up protons and neutrons, the nucleus of the atom.
Leptons are particles of matter which appear to be point-like, without internal structure. Half of the six carry a charge- for example, the electron which has a negative charge, and the other 3 are types of neutrinos. Until now - if this finding turns out to be correct, it was believed that neutrinos have almost no mass, and no electrical charge meaning they don't interact much with anything at all, making them very difficult to find.
Neutrinos - the top line in green in the chart, are most often produced as other particles decay, in a radioactive process. They were produced in huge amounts in the very early universe and abound today. The neutrino is the particle you hear about that can pass right through the earth without a single interaction. There are millions of neutrinos passing through your hand as you read this. From a neutrino's eye-view, we are mostly empty space.
Finally, all particles have rules- what they can and cannot do, how they match or mismatch one another. The rules are based on fundamental laws of the universe. By knowing these rules, we can put particles into accelerators like Fermi and Cern, take images of the collisions which happen near the speed of light, and learn more about them.
So now, back to the Fermi Lab findings. Mathematical computations predict what particles should be seen, and how they'll look. Most of the time, the predictions are accurate and show exactly what is expected, once the particle is found. That is good evidence supporting the SM. But if a particle gives evidence of properties which are inconsistent with the rules, then "Houston, we have a problem". First, of course, the new findings must be verified and repeatable. It could be a mistake. But if it's not a mistake, then we know that there's an error in the rules, which must be adjusted to include the new data. What's truly exciting is that if one rule has to be changed, usually there's a domino effect and one really doesn't know how far it will go.
That's what we're looking at here, with Fermi's scientists the finding is that the antiparticles of the neutrinos in the experiments have mass - not just a tiny bit more, but tremendously more than their neutrino counterpart. Science has wonderful names which describe assorted properties; in this case we're talking about flavors of neutrinos.
From John Timmer's article
Two weeks ago, experimental results seemed to indicate that we're getting a handle on the low-mass particles called neutrinos. Today, Fermilab announced results generated using anti-neutrinos that suggests we may need to make major revisions to the Standard Model of physics. The textbook description of antimatter is that it's like a mirror image of more familiar particles. But new work from Fermilab indicates that the mass differences among anti-neutrinos aren't the same as those for regular neutrinos. If the findings hold up, they would call for some new physics to explain the discrepancy.
Like the earlier results, the new data relies on observations of neutrino flavor changes. Neutrinos and anti-neutrinos, unlike other particles, appear not to have a fixed nature. They exist as a mixture of three identities--electron, muon, and tau--and a given particle oscillates among these identities in a probabilistic manner that depends in part on the mass differences among the three classes. So, if we can observe these oscillations, we can get some indication of the relative masses of these extremely light particles.
Scientists from the MINOS team presented some preliminary results of their work at a meeting being held in Athens (the catchy meeting name: Neutrino 2010). The release announcing them cautions that the data is only just approaching statistical significance, and will require extensive confirmation work, not to mention a trip through peer review before publication. Those cautions aside, the results are pretty intriguing, since they suggest something very strange is up with the neutrinos' masses.
Right now, we can't directly measure the masses of the neutrinos very precisely, but we can get a sense of how the masses differ among the three flavors. The MINOS experiment only produces muon neutrinos and their antimatter counterparts, but on their way to Minnesota some of these will change flavor. This oscillation is governed in part by the relative masses of the different flavors, providing researchers with a glimpse into the particles' masses.
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