The elusive neutrino
If you think that vacuum is a real emptiness, then you are very mistaken. Even the cold interstellar space, not to mention the artificially created vacuum, is not so empty. For one cubic meter of the Universe on average there is one proton and one electron. Even in the same cube, there are an average of 500 million relict photons and as many relict neutrinos. Our Universe not only shines from within, from the first millisecond of the Big Bang, but also “neutrins” just as intensely.
Are you intrigued? Did you know that:
Predicted theoretically, a particle could be observed only by indirect methods. If now such an approach practically does not raise doubts among physicists, then more than half a century ago, evidence was considered ephemeral and doubtful. What is the problem? The fact that neutrinos are extremely difficult to catch directly. The classical neutrino experiment is the reverse beta decay:
antineutrino + proton -> positron + neutron + photons.
Subsequently, the neutron was captured by the substance of the detector with the release of photons. That is, two flashes of light following at intervals is a sign of an antineutrino. Would you believe
Neutrino detectors are located in the bulk of the substance - in the mountains, in the ice of Antarctica, in the mines - precisely to exclude any side channels of the formation of "flashes", except for the all-penetrating neutrino channel. A water detector is a convenient container for capturing neutrons. Simply put, a neutrino detector is a gigantic ice cube (scintillator), into which spokes from photon detectors are inserted, recording the smallest emission of radiation.
Two flashes - that's the neutrino. It is hard to believe, but there have been many such experiments, statistics have been compiled. And most importantly, the neutrino was only the first sign in the new model of theoretical physics, when the theory went ahead of the experiment, and predicted the existence of particles and effects long before their experimental confirmation. The neutrino was theoretically invented, “fitted” in properties to explain the discrepancies in the experiment, and only then indirectly discovered. You cannot touch and measure a neutrino with a common arshin, it is so special, and you can only believe in it :)
The physical uniqueness of neutrinos is in the absence of an electric charge (does not participate in electromagnetic interactions) and “color” (not subject to quantum chromodynamics). The remaining “weak” and gravitational interactions are a million and 10 ^ 38 degrees respectively less intense than the “strong” one. As a result, a neutrino travels through the Universe, piercing matter and time, having extremely low chances of being noticed and “captured” by another particle. Also, other leptons (electron, muon and taon) that are not subject to chromodynamics have an electric charge, and are not suitable for the role of eternal travelers in space.
By the way, about the uniqueness of neutrino disputes are no less stormy. If it is truly neutral in every sense, what is antineutrino? And what is their difference? After all, if an electron has a negative electric charge that is familiar to us (it is also a convention, by the way - you could call a positron an electron, and vice versa), then a neutrino does not have any charges. It can be absolutely accurately said that the choice of particle and antiparticle in this case was completely arbitrary, terminological. The differences between the neutrino and the antineutrino had to be explained to the Nobel laureate Landau and his theory of deep CP symmetry (symmetry in charge-parity). True, in 1964 they successfully proved the violation of CP symmetry in the decay of the neutral kaon, which ultimately led to the prediction of the third generation of quarks, but this is a different story. It is believed that a series of experiments did not find any reactions that contradict the fundamental difference between neutrinos and antineutrinos,
The search for differences between neutrinos and antineutrinos and the so-called lepton charge led to a theoretical assumption, proved experimentally in 1962 - neutrinos are not so neutral as originally supposed. It has a lepton charge, and all leptons are divided into families (three in the modern Standard Model, and at that time the first two were known), and the neutrino is electronic, muon and taonic. The physical consequences of this discovery is very interesting - because the particles allow the family to build a grand unified theory of matter and of evolution, but we note that the neutrino for our simple tour - this is not one particle, but three (plus three of their anti hearth).
What else is interesting neutrino? For example, neutrino physics does not require the investment of trillions of dollars and the construction of the Large Hadron Collider. In the fifth year, every week we went to Protvino on the U-70 proton synchrotron, which is regularly used today for scientific experiments. The complex of Tagged Neutrino, an advanced breakthrough of physical thought in those years, and now has not lost its relevance.
But in addition to accelerators and relict background, there are still powerful sources of neutrinos - stars. Observation of neutrinos emitted by stars proved the thermonuclear nature of stars - which, generally speaking, is not obvious - because there are many types of stars, and our sun is not the most representative and interesting among them. And neutrino astronomy is a real science. Firstly, neutrinos form in stars (remember the teaser at the beginning? Neutrino is an obligatory component of the thermonuclear reaction), and secondly, they flash other stars through and through and reach the Earth. Which, theoretically, can give us information from the most stellar bowels. Neutrino telescopes are actually deep in the Earth’s thickness, and they detect the flow of particles passing through the Earth’s thickness from the reverse side of it! Such telescopes operate in many countries, including Russia -BAIKAL at a depth of 1 km in the waters of Lake Baikal, and Baksan in the Caucasus.
From the realm of science fiction (but not abstract, but limited only by the sensitivity of instruments), it is neutrino astronomy that can prove the existence of anti-worlds - galaxies entirely consisting of antimatter. After all, “anti-stars” generate the same indistinguishable stream of standard photons as ordinary stars. But the most powerful neutrino stream from them will all have the prefix “ anti ”. Also, the neutrino telescope can very well determine the collapse of a star (into a supernova, black hole or into a dwarf) within our Galaxy.
And for dessert: two more paradoxes and many theories are connected with neutrinos, which are currently impossible to confirm or refute. The neutrino flux from the sun has been consistently less than theoretically calculated, for many decades. The theory trying to explain the shortage is neutrino oscillation, the transformation of one type into another (electronic to muon), the lepton charge not being saved, respectively, the symmetry and triumph of the supporters of the Great Unification theories flying to hell, for which everyone is equal (but only at high energies) . But if the neutrinos oscillate, then they have a nonzero (and different) mass. A non-zero mass of neutrinos will complicate the life of theoretical physicists, but astronomers will breathe freely - they don’t have a debit with credit, the observed mass of the Universe is critically less than what is theoretically necessary.
This concludes the brief popular science introduction to neutrino physics, if successful, I can continue to recall the student years at the physics department :)
Are you intrigued? Did you know that:
- The neutrino is an integral part of the thermonuclear reaction that gives life to the stars.
- Antineutrino carries about 2% of the energy of a nuclear reactor to the vastness of the Galaxy.
- The familiar “neutron” could symbolize a neutrino if the debate about the existence of a mysterious particle would not drag on before the discovery of a real neutron.
Predicted theoretically, a particle could be observed only by indirect methods. If now such an approach practically does not raise doubts among physicists, then more than half a century ago, evidence was considered ephemeral and doubtful. What is the problem? The fact that neutrinos are extremely difficult to catch directly. The classical neutrino experiment is the reverse beta decay:
antineutrino + proton -> positron + neutron + photons.
Subsequently, the neutron was captured by the substance of the detector with the release of photons. That is, two flashes of light following at intervals is a sign of an antineutrino. Would you believe
Neutrino detectors are located in the bulk of the substance - in the mountains, in the ice of Antarctica, in the mines - precisely to exclude any side channels of the formation of "flashes", except for the all-penetrating neutrino channel. A water detector is a convenient container for capturing neutrons. Simply put, a neutrino detector is a gigantic ice cube (scintillator), into which spokes from photon detectors are inserted, recording the smallest emission of radiation.
Two flashes - that's the neutrino. It is hard to believe, but there have been many such experiments, statistics have been compiled. And most importantly, the neutrino was only the first sign in the new model of theoretical physics, when the theory went ahead of the experiment, and predicted the existence of particles and effects long before their experimental confirmation. The neutrino was theoretically invented, “fitted” in properties to explain the discrepancies in the experiment, and only then indirectly discovered. You cannot touch and measure a neutrino with a common arshin, it is so special, and you can only believe in it :)
The physical uniqueness of neutrinos is in the absence of an electric charge (does not participate in electromagnetic interactions) and “color” (not subject to quantum chromodynamics). The remaining “weak” and gravitational interactions are a million and 10 ^ 38 degrees respectively less intense than the “strong” one. As a result, a neutrino travels through the Universe, piercing matter and time, having extremely low chances of being noticed and “captured” by another particle. Also, other leptons (electron, muon and taon) that are not subject to chromodynamics have an electric charge, and are not suitable for the role of eternal travelers in space.
By the way, about the uniqueness of neutrino disputes are no less stormy. If it is truly neutral in every sense, what is antineutrino? And what is their difference? After all, if an electron has a negative electric charge that is familiar to us (it is also a convention, by the way - you could call a positron an electron, and vice versa), then a neutrino does not have any charges. It can be absolutely accurately said that the choice of particle and antiparticle in this case was completely arbitrary, terminological. The differences between the neutrino and the antineutrino had to be explained to the Nobel laureate Landau and his theory of deep CP symmetry (symmetry in charge-parity). True, in 1964 they successfully proved the violation of CP symmetry in the decay of the neutral kaon, which ultimately led to the prediction of the third generation of quarks, but this is a different story. It is believed that a series of experiments did not find any reactions that contradict the fundamental difference between neutrinos and antineutrinos,
The search for differences between neutrinos and antineutrinos and the so-called lepton charge led to a theoretical assumption, proved experimentally in 1962 - neutrinos are not so neutral as originally supposed. It has a lepton charge, and all leptons are divided into families (three in the modern Standard Model, and at that time the first two were known), and the neutrino is electronic, muon and taonic. The physical consequences of this discovery is very interesting - because the particles allow the family to build a grand unified theory of matter and of evolution, but we note that the neutrino for our simple tour - this is not one particle, but three (plus three of their anti hearth).
What else is interesting neutrino? For example, neutrino physics does not require the investment of trillions of dollars and the construction of the Large Hadron Collider. In the fifth year, every week we went to Protvino on the U-70 proton synchrotron, which is regularly used today for scientific experiments. The complex of Tagged Neutrino, an advanced breakthrough of physical thought in those years, and now has not lost its relevance.
But in addition to accelerators and relict background, there are still powerful sources of neutrinos - stars. Observation of neutrinos emitted by stars proved the thermonuclear nature of stars - which, generally speaking, is not obvious - because there are many types of stars, and our sun is not the most representative and interesting among them. And neutrino astronomy is a real science. Firstly, neutrinos form in stars (remember the teaser at the beginning? Neutrino is an obligatory component of the thermonuclear reaction), and secondly, they flash other stars through and through and reach the Earth. Which, theoretically, can give us information from the most stellar bowels. Neutrino telescopes are actually deep in the Earth’s thickness, and they detect the flow of particles passing through the Earth’s thickness from the reverse side of it! Such telescopes operate in many countries, including Russia -BAIKAL at a depth of 1 km in the waters of Lake Baikal, and Baksan in the Caucasus.
From the realm of science fiction (but not abstract, but limited only by the sensitivity of instruments), it is neutrino astronomy that can prove the existence of anti-worlds - galaxies entirely consisting of antimatter. After all, “anti-stars” generate the same indistinguishable stream of standard photons as ordinary stars. But the most powerful neutrino stream from them will all have the prefix “ anti ”. Also, the neutrino telescope can very well determine the collapse of a star (into a supernova, black hole or into a dwarf) within our Galaxy.
And for dessert: two more paradoxes and many theories are connected with neutrinos, which are currently impossible to confirm or refute. The neutrino flux from the sun has been consistently less than theoretically calculated, for many decades. The theory trying to explain the shortage is neutrino oscillation, the transformation of one type into another (electronic to muon), the lepton charge not being saved, respectively, the symmetry and triumph of the supporters of the Great Unification theories flying to hell, for which everyone is equal (but only at high energies) . But if the neutrinos oscillate, then they have a nonzero (and different) mass. A non-zero mass of neutrinos will complicate the life of theoretical physicists, but astronomers will breathe freely - they don’t have a debit with credit, the observed mass of the Universe is critically less than what is theoretically necessary.
This concludes the brief popular science introduction to neutrino physics, if successful, I can continue to recall the student years at the physics department :)