An even more elusive variant, the famous “ ghost particle », the neutrinohas just emerged in a fascinating study that is full of profound implications; according to its authors, sterile neutrinos could be indirectly at the origin of all the matter contained in the Universe, and make it possible to resolve an old enigma which has resisted the attacks of physicists for decades.
To understand the ins and outs of this work, we must first ask ourselves a question which may seem silly at first, but which is in fact much deeper than it seems: why is the Universe filled with matter?
Matter-antimatter asymmetry, a major mystery of modern physics
If this question is entirely legitimate, it is because standard matter, that with which we interact on a daily basis, is only the tip of the iceberg. Each particle described in the standard model has in fact an almost identical twin, with the exception of its charge which is opposite; all this menagerie constitutes what we call antimatter, a concept proposed by the illustrious physicist Paul Dirac at the end of the 1920s.
The most remarkable property of these objects lies in their interactions with ordinary matter. When a conventional particle meets its anti-twin, they annihilate each other by releasing a large amount of energy in the form of gamma rays.
This mechanism is today very well supported by theory, but also by a large amount of experimental evidence which leaves almost no room for interpretation. But this also poses another particularly thorny problem.
Indeed, the first models describing the evolution of the universe considered that matter and antimatter had been created in perfectly equal quantities at the time of the Big Bang. But if that were the case, the Universe as we know it would simply not existand for good reason: all the constituents of matter would have been promptly annihilated during their meetings with their anti-twins! Now, since you are reading this article, it is inevitable that part of ordinary matter survived this original cataclysm.
This inconsistency has pushed physicists to reconsider part of this scenario. Today, it is estimated thatan imbalance allowed ordinary matter to emerge in greater quantities than antimatter. An interpretation that is certainly coherent… but which also brings its share of problems. After a century of concerted effort by the greatest visionaries in the history of science, no one has succeeded in determining the origin of this asymmetry.
Of neutrinos « right-handed » who are conspicuous by their absence
This is where a new study recently pre-published on arXiv, spotted by physicist and popularizer Paul Sutter, comes in. According to its authors, the key to the mystery could lie in a family of extremely discrete particles, namely the neutrinos.
These objects are themselves very mysterious in many ways. If they are relatively poorly known compared to the other particles of the standard model, it is because it is very difficult to get your hands on them. In addition to their incredibly low mass, they only seem to respond to two forces: gravity and the weak interaction. Therefore, they are able to pass through large amounts of physical matter, such as entire planets, without leaving a single trace! It goes without saying that it is incredibly difficult to detect them, and therefore study them; no wonder they inherited the nickname ” ghost particles ».
Another characteristic of neutrinos which leaves physicists perplexed concerns their structure, and is based on the notion of chirality. To illustrate this, we can take the example of the human hand. Your two appendages have exactly the same bones, tendons, muscles, cartilage and nerves, and they are (ideally) arranged in the same structure: no matter which hand you choose, the index finger is always connected to the palm and is located between middle finger and thumb. But it only takes a glance to see a major difference: you have a left hand and a right hand that are symmetrical to each other. If you place your left hand on your right hand, or vice versa, they do not overlap.
This distinction also exists for many so-called chiral molecules and particles; like our hands, there are left (levorotatory) and right (dextrorotatory) variants, which have atomic structures or opposite spin. This is the case for neutrinos… except that the three known variants are all levorotatory! To date, no one has ever found the slightest trace of a neutrino ” right-handed », also called sterile neutrino, even though they occupy a significant place in current cosmological models.
From the neutrino to the Majoron, a new candidate for dark matter
A detail that is not trivial for the authors of this new study, who saw a potential link with the asymmetry between matter and antimatter.
In their paper, they proposed a model where these two families of neutrinos coexisted in perfectly equal quantities at the very beginning of the universe, almost 14 billion years ago — a bit like the matter/antimatter couple. As the cosmos expands and cools, a disturbance, however, would have disrupted this balance, leading to the disappearance of these right-handed neutrinos.
This is an interesting hypothesis, because it would help explain why the latter seem impossible to observe today. But the laws of physics as we know them obviously prohibit them from disappearing without leaving the slightest trace. For the authors, they would in fact merged to form a whole new class of hypothetical particles, Majorons. And the least we can say is that it is a particularly exotic object: still according to this model, it would be its own antiparticle!
These majorons would then have survived discreetly since this primordial era. According to the researchers’ calculations, they now make up most of the mass of each galaxy, while remaining invisible and elusive. Does this definition remind you of anything? This is normal: This is very similar to the way dark matter is described today.this still hypothetical entity which has been formalized to explain flagrant inconsistencies between observable reality and the models which describe the structure and behavior of galaxies. Therefore, this model also places the Majoron as a prime candidate for dark matterthe exact nature of which remains unknown (assuming that it indeed exists).
The key to the great asymmetry?
Finally, the chain reaction which led to the emergence of majorons would have had a final consequence at least as important. In addition to transforming these right-handed neutrinos, the researchers suggest that it also upset the delicate balance that existed between matter and antimatter, leading to the asymmetry which allowed the former to continue to exist to form the Universe as we know it today!
As you will have understood, this is a daring model which is full of excessively deep implications. Unfortunately, it will be difficult to validate or refute it. To achieve this, we will have to wait to detect either a Majoron or one of these famous right-handed neutrinos which would have escaped the chain reaction – which is anything but a guarantee. But the game is worth it; If one of the currently active neutrino detectors one day detects a signal compatible with this scenario, we will therefore be on the royal road to solving several great cosmological mysteries in one fell swoop. An obviously very exciting prospect for all physicists. It will therefore be appropriate to follow the work of physicists who will attempt to validate or refute this fascinating model.
The study text is available here.
🟣 To not miss any news on the WorldOfSoftware, , .
