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Scientists are passionate about exploring mysteries, and the greater the mystery, the greater the enthusiasm. There are many unanswered scientific questions, but when you're fat, it's hard to beat "Why is there anything instead of nothing?"
This may sound like a philosophical question, but it is a question that lends itself very well to a scientific inquiry. More concretely, "Why is the universe composed of the types of materials that make human life possible, so that we can even ask that question?" Scientists conducting research in Japan announced last month a measure that directly responds to the most fascinating of the surveys. It seems that their measure disagrees with the simplest expectations of the current theory and may well indicate an answer to this timeless question.
Their measurement suggests that for a particular set of subatomic particles, matter and antimatter act differently.
Matter against Antimatter
Using the J-PARC accelerator, located in Tokai, Japan, scientists projected a ghostly subatomic particle beam called neutrinos and their antimatter counterparts (antineutrinos) across the Earth up to the end of the day. Super Kamiokande experience, located in Kamioka, also in Japan. This experiment, called T2K (Tokai to Kamiokande), is designed to determine why our universe is made of matter. A particular behavior of neutrinos, called neutrino oscillation, could shed some light on this very thorny problem. [The 18 Biggest Unsolved Mysteries in Physics]
Asking the question of why the universe is made of matter may seem like a strange question, but there is a very good reason for scientists to be surprised at this. This is because in addition to knowing the existence of matter, scientists also know about antimatter.
In 1928, British physicist Paul Dirac proposed the existence of antimatter – an antagonistic brother of matter. Combine equal amounts of matter and antimatter and both annihilate, releasing a tremendous amount of energy. And, as the principles of physics generally work in the opposite way, if you have a prodigious amount of energy, it can be converted into exactly equal amounts of matter and antimatter. Antimatter was discovered in 1932 by the American Carl Anderson and researchers have had nearly a century to study its properties.
However, this phrase "in exactly equal quantities" is the crux of the puzzle. In the brief moments that immediately followed the Big Bang, the universe was full of energy. By developing and cooling, this energy should have been converted into equal parts of matter and subatomic antimatter particles, which should be observable today. And yet, our universe is essentially made up entirely of matter. How can this be?
By counting the number of atoms in the universe and comparing it to the amount of energy we see, scientists have determined that exactly "exactly equal" is not absolutely correct. In one way or another, while the universe was about a billionth of a billionth of a second, the laws of nature were slightly biased in the sense of matter. For 3,000,000,000 particles of antimatter, there were 3,000,000,000 particles of matter. The 3 billion particles of matter and the 3 billion particles of antimatter have combined – and have been annihilated in energy, leaving the slight excess of matter in the composition of the universe that we see today.
Since this puzzle was understood nearly a century ago, researchers were studying matter and antimatter to see if they could find behavior in subatomic particles that could explain the problem. excess of matter. They are convinced that matter and antimatter are manufactured in equal amounts, but they also observed that a class of subatomic particles, quarks, exhibits behaviors that slightly favor the material compared to the other. ;antimatter. This particular measurement was subtle, involving a class of particles called K mesons that can convert matter to antimatter and vice versa. But there is a slight difference between matter converted to antimatter and the reverse. This phenomenon was unexpected and its discovery led to the 1980 Nobel Prize, but the magnitude of the effect was not enough to explain why matter dominated in our universe.
Ghostly Beams
Scientists turned to neutrinos to see if their behavior could explain the excess of matter. Neutrinos are the ghosts of the subatomic world. Interacting only by the weak nuclear force, they can cross matter without interacting almost ever. To give an idea of the scale, neutrinos are most often created during nuclear reactions and the largest nuclear reactor in the world is the Sun. Protecting yourself from half of the solar neutrinos would take a solid lead mass about 5 light-years deep. Neutrinos do not really interact very much.
Between 1998 and 2001, a series of experiments – one using the Super Kamiokande detector and another using the SNO detector in Sudbury, Ontario – proved conclusively that neutrinos also exhibited other surprising behavior. They change their identity.
Physicists know three distinct types of neutrinos, each associated with a single subatomic brother, called electrons, muons and taus. Electrons are the cause of electricity and the particles of muon and tau are very similar to electrons, but are heavier and more unstable.
The three types of neutrinos, called electron neutrino, muon neutrino and neutrino tau, can be "transformed" into other types of neutrinos and vice versa. This behavior is called neutrino oscillation. [Wacky Physics: The Coolest Little Particles in Nature]
The oscillation of neutrinos is a particularly quantum phenomenon, but it is roughly analogous to that of a bowl of vanilla ice cream and, once you have found a spoon, you will find that the bowl is half vanilla and half chocolate. Neutrinos change their identity from one type to another, into a mix of types, into a totally different type, and then back to the original type.
Antineutrino oscillations
Neutrinos are particles of matter, but there are also neutrinos of antimatter, called antineutrinos. And that raises a very important question. Neutrinos oscillate, but do antineutrinos also oscillate in exactly the same way as neutrinos? The answer to the first question is yes, while the answer to the second one is not known.
Let's examine this a little more deeply, but in a simplified way: suppose that there are only two types of neutrinos: the muon and the electron. Suppose further that you have a purely muon-type neutrino beam. Neutrinos oscillate at a specific speed and, as they get closer to the speed of light, they oscillate according to the distance at which they were created. Thus, a pure muon neutrino beam will look like a mixture of muon and electron types at a distance, then of purely electron types at another distance and then return to the muon alone. The antimatter neutrinos do the same thing.
However, if the neutrinos of matter and antimatter oscillate at slightly different speeds, you would expect that, if you were at a fixed distance from the point of creation of a neutrino beam at pure muons or muon antineutrinos, you would see a mixture of muon neutrinos and electrons, but in the case of antimatter neutrinos, you would see a different mixture of muon neutrinos and d & # 's; 39, antimatter electrons. The actual situation is complicated by the fact that there are three types of neutrinos and that the oscillation depends on the energy of the beam, but these are the big ideas.
The observation of different oscillation frequencies by neutrinos and antineutrinos would be an important step in understanding the fact that the universe is made of matter. This is not the whole story, because new phenomena must be taken into account, but the difference between neutrinos of matter and antimatter is necessary to explain why there is more matter in the universe. [5 Mysterious Particles That May Lurk Beneath Earth’s Surface]
In the current theory describing interactions between neutrinos, there is a variable sensitive to the possibility that neutrinos and antineutrinos oscillate differently. If this variable is equal to zero, the two types of particles oscillate at identical rates; if this variable differs from zero, the two types of particles oscillate differently.
When T2K measured this variable, they found that it was inconsistent with the hypothesis that neutrinos and antineutrinos oscillate identically. A little more technically, they determined a range of possible values for this variable. There is a 95% chance that the true value of this variable is in this range and only 5% that the true variable is outside this range. The "no difference" assumption is outside the 95% range.
In simpler terms, current measurements suggest that neutrinos and antimatter neutrinos oscillate differently, although certainty does not reach the level required to make a definitive statement. In fact, critics point out that measures with this level of statistical significance must be viewed with great skepticism. But it is certainly an extremely provocative initial result, and the global scientific community is extremely interested in improved and more accurate studies.
The T2K experiment will continue to record additional data in the hope of making a definitive move, but it's not the only game in town. At Fermilab, located outside of Chicago, a similar experiment called NOVA aims to neutralize neutrinos and antimatter neutrinos in northern Minnesota, in hopes of beating T2K. And, more oriented towards the future, Fermilab is actively working on what will be its flagship experience, dubbed DUNE (Deep Underground Neutrino Experiment), which will have much better capabilities to study this important phenomenon.
Although the result of T2K is not definitive and it is necessary to be cautious, it is certainly tempting. Given the enormity of the question of why our universe does not seem to have significant antimatter, the global scientific community will look forward to further updates.
Originally posted on Live Science.
Don Lincoln is a physics researcher at Fermilab. He is the author of "The Large Hadron Collider: The extraordinary story of the Higgs boson and other elements that will blow up your mind" (Johns Hopkins University Press, 2014), and produced a series of videos on science education. Follow it on Facebook. The opinions expressed in this comment are his.
Don Lincoln contributed this article to Live Voices Expert: Op-Ed & Insights.
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