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The Era of The Neutrino

Prior to 1945, studies of radioactive phenomena in which nuclei decay and beta particles are released. Physicists have found that beta particles can have many different energies, although the theory states that All beta particles must have the same energy. When the experimental results and the theory’s predictions conflict, Wolfgang Pauli offers a solution: When the nucleus of a radioactive element decays to a beta particle.

The nucleus doesn’t just emit beta particles. But there is another particle that has neither charge nor mass. The distribution of energy to this mysterious particle Sometimes more and sometimes less, so the beta particles have some and some less energy, as the experimenters saw. Pauli’s proposal was so unacceptable that physicists were able to capture the mysterious particle.

Until 1957, Enrico Fermi proposed the theory of radioactive decay. and named this secret particle neutrino, although no one has seen it because the particle has no mass. and has no charge, but has energy (light is another massless particle but has energy), so it rarely interacts with particles, yet most physicists believe that nature has certain neutrinos.

In 1971, Frederick Reines and Clyde Cowan succeeded in capturing neutrinos for the first time. And this achievement earned the Rhineness half of the 1995 Nobel Prize in Physics, and Kovan did not. because he died before

The main source of neutrinos is the sun, which Hans Bethe described as neutrinos formed when the nucleus of hydrogen Fusing to form helium, or caused by collision between cosmic rays and air molecules in the Earth’s atmosphere. or when protons are accelerated to hit heavy metal targets Including being born in an atomic reactor, so Raymond Davis (Raymond Davis) of the University of Pennsylvania in the United States tried to capture and count the number of nuclei in the sun.

By taking a tank with a volume of 380 m3, which contained perchloroethylene solution. The 615 tons of pure perchloroethyene: CC was buried 1,500 meters underground in the Homestake gold mine in South Dakota. this Davis was dubbed “Cowboy Physicist” because the working area is far from the light and civilization which is not like a typical physicist’s workplace

Davis knew that fusion neutrinos in the sun, traveling through space, collide with the chlorine atoms in the C 2 Cl 4 molecule , convert the chlorine adomin to argon atoms as in the v+ Cl reaction. 37 -> Ar 37 + e – Because the argon atom is a radioactive atom with a life of about 50 days, Davis was able to see the argon atom. and the theory predicts that Out of the chlorine atoms in a 10″ tank, only 6-8 atoms will react with neutrinos. Then 6-8 argon atoms are formed, but Davis only sees 2.1 + 0.3 atoms, which is 1/3 of the expected value.

When the numbers obtained from the experiment were like this A possible conclusion is Theorists miscalculate the rate of nuclear reactions. which shouldn’t be Because the same theory can explain other nuclear reactions very well. Or Davis’s results were flawed because two-thirds of the neutrinos had escaped, but Davis’ functional analysis showed no flaws. This paradox led to a crisis. big time in physics

It wasn’t until 1987 when Masatoshi Koshiba of the Kamiokande Laboratory in Japan succeeded in detecting neutrinos from supernovas. ) 1987A Then Tai turned his attention to the study of neutrinos from the Sun. And Koshiba’s measurements are consistent with Davis’s experiments: neutrinos coming from the Sun are only 0.403 + 0.013 of the calculated values.

Theoretical physicists are trying to find a solution to this paradox. Bruno Pontecorvo suggests that If the universe has three kinds of neutrinos (3 flavors) i.e. electron neutrino, muon neutrino and tau neutrino, which usually occur together with eectron, muon and tau particles respectively and these three neutrinos are uncharged whereas electrons , muon and tau are negatively charged. Having different masses of the three neutrinos can cause one neutrino to mutate to another as it travels.

So in 2002, Raymond Davis of the University of Pennsylvania The United States and Masatoshi Koshiba of the University of Tokyo have thus received half of the award in Bel Physics for opening up the world of neutrino astronomy as the primary factor for exploration and Study of phenomena in the universe

A neutrino differs from an electron particle, a muon, and a tower particle in that it has an unstable mass. Neutrinomuons and neuters in the town are mixed in different ratios Because the masses of the three neutrinos change at different speeds. where the switching speed depends on the different mass. neutrino energy and a constant that determines the rate of change.

In the Standard Model of physics, all three types of neutrino particles and photons have no mass. Therefore, the velocity of neutrinos must be the speed of light. But if a neutrino can change, it has to have mass and therefore has a lower speed than light.

Measuring the masses of the three neutrinos is a very important issue in physics. and made underground physics a popular issue, because in 1998 a research team of 120 physicists led by Takaki Kajita of the University of Tokyo of the Supercameokan Laboratory the (Super-Kamiokande), which the Japanese government has created with 4 money. Ten billion baht has announced the results of experiments showing that neutrinos have mass.

Kachita came to this conclusion from an experiment in which a 50,000-ton tank of pure water was buried one kilometer underground in a zinc mine 250 km away from Tokyo, with a photomultiplier tube on the walls. r 13,000 photomutipliers for the light produced when muon neutrinos interact with water protons in a tank.

Installing a tank at such a depth Because Kajita wanted to block other particles from reacting with the water in the tank and using large amounts of water. This increases the likelihood of interaction between muon neutrinos and protons. As for the installation of tens of thousands of photomultipliers around the tank to be able to accurately determine the direction and origin of the neutrinos.

The results showed that The number of neutron particles from the Sun at ground level is greater than at high altitude. That is, the muon neutrino has changed, so it has about 10 million times less mass than an electron.

Arthur McDonald of Queen’s University in Kingston, Canada confirmed Kachita’s discovery using the Sudbury Neutrino Observatory (SNO) laboratory. ) with a spherical device containing 1,000 tons of heavy water. word Some electron neutrinos become muons and neutrinos. comparable to Someone threw a lemon But when it comes to our hands, the lemon has turned into a mango.

The whole experiment At Super-Kamiokande and at SNO, Kachita and McDonald were awarded the 2015 Nobel Prize in Physics together.

To make the experiments measure different masses of neutrinos smoothly. Instead of having to wait for it from far away space, physicists have built a laboratory on Earth capable of producing large quantities of neutrinos. By firing a proton at a graphite target, it produces charged, short-lived muon particles and a large number of muon neutrinos are formed and then focused the beam. Anneutrino has to rush to the Super Kameokande Laboratory.

Super-Kamiokande at the commercial town of Kamioka, 295 km away. The neutrino probe at the destination found six electron neutrinos, that is, a muon neutrino. change to electron neutrino Therefore, neutrinos have mass.

The next puzzle is: what causes neutrinos to have mass? The Standard Model did not consider the interaction between the Higgs particle and the neutrino, so the model had to be revised to explain why the three types of neutrinos. have different masses

Chinese physicists interested in neutrinos have asked the government to build a 10.5 billion baht Jiangmen Underground Neutrino Observatory (JUNO) in the provincial city of Jiangmen. Guangdong to measure the masses of all three neutrinos. and expect an answer in 2020.

American physicists also have a project to measure the mass of neutrinos. With three times the resolution and accuracy of China, the American project is scheduled to take effect by 2025 using 40,000 tons of liquid argon detectors that will provide electrons and light. When an argon atom is hit by a neutrino

Other nations of physicists are interested in neutrinos. For example, Argentina’s Pierre Auger observatory in Mendoza measures the energy of neutrinos from space in the range of 10′-1031 electron volts. It uses 1600 small water tanks and this lab has been operating since 2004.

In Antarctica there is the McMurdo Station (McMurdo), which launches balloons high into the atmosphere to detect neutrinos with energy of 10 17 – 10 21 electron volts.

At the South Pole, the ICECUBE project uses 1 cubic kilometer of ice at a depth of 1.5 kilometers to capture neutrinos with energies ranging from 10′-10’1 electron volts. working under ice instead of orbiting in the sky like a conventional telescope and at this very depth The pressure of the ice is so high that there are no air bubbles inside the ice. and when the atmosphere surrounding the ice block was completely dark So if there is light.

The experimenter will immediately know that The neutrino has hit the oxygen atom in the water. causing a muon to form which will illuminate photomultiplier that are lined around the ice block. It is also a device used to study dark matter and WIMP (weakly interacting massive particle), so if WIMP is found, the ICECUBE project leader is ready to travel to receive the Nobel Prize.

Japan is also planning to build a Hyperkamio Kande Laboratory. (Hyper-Kamiokande) worth 28 billion baht, which will be the largest neutrino detection device in the world. Being 25 times larger than Super Kameokande, the device used 106 tons of pure water to obtain neutrinos from the Japan Proton Accelerator Research Complex (J-Parc). J-Parc

Theorists are interested in In nature, there may be a type 4 neutrino, a sterile neutrino, that would react with other particles less strongly than all neutrinos if this type 4 neutrino were real. Physics will explain the origin of dark matter. If any neutrinos vanish without a trace, that means It has become a barren neutrino. And to my surprise, physicists are using near-massless particles to study the most massive system, the universe.

This article is part of NSTDA Magazine.