Electrons are one of the main components of the atoms that make up the world around us. It is the electrons surrounding each nucleus that determine how the chemical reaction proceeds. In practical applications, electronics, from electronic equipment, welding, to microscopic imaging, particle accelerators, etc., have a wide range of applications in various fields. Recently, a physics experiment conducted by a number of universities in the United States, called “Advanced Cold Molecular Electron Dipole Moment” (abbreviated as ACME), whose experimental equipment is only table size, once again put small electrons in scientific research. At the forefront, and trying to find new particles by detecting the “shape” of the electrons. Is the electron really shaped? What does this have to do with new particles? Let’s talk about it below.
Classic shapes and quantum shapes What is the shape of the electron? If you recall the pictures in a high school textbook, the answer seems clear: electrons are a small, negatively charged ball. However, this is far from the truth. Elementary particles, without any internal structure, so the word “shape” has no meaning for electrons. To make “shape” meaningful to electronics, we must adjust the definition of “shape” so that it can be used in the quantum world. In our macro world, seeing all kinds of shapes actually means that we have detected the light reflected from the surrounding objects with our eyes, and the light is just an electromagnetic wave. In other words, the shape is actually an object. A reaction under the action of an electromagnetic field. We can magnify the concept of “shape” and treat properties that can be described in any electromagnetic field as “shapes.” Although this may be a very strange way of describing “shapes”, because of the many properties of electrons, including charge, spin, etc., it can describe how it reacts under the action of an electromagnetic field. Maybe we can think of one of these attributes as the “shape” of the electron.
So which property is best suited as the “shape” of the electron? The property chosen by the physicist is the electric dipole moment. Electron dipole moment In classical physics, the electric dipole moment is a physical quantity that measures the distribution of positive and negative charges in a system. If the positive charge distribution is separated from the negative charge distribution, the electric dipole moment is no longer zero. For example, a uniformly charged sphere has no positive and negative charge separation and its electric dipole moment is zero. But imagine a dumbbell with one side with a positive charge and the other with a negative charge, then the dumbbell has a non-zero electric dipole moment. In addition to the charge, the number of electric dipole moments determines how the system responds to the applied electric field. For macroscopic objects, the distribution of positive and negative charges is usually related to the shape of the object. For electronics, it has no real shape, but to understand its electric dipole moment, physicists usually imagine it has a shape. For example, if the electric dipole moment of an electron is zero, we regard it as a uniformly charged sphere; if the electric dipole moment has a certain value, then the electron is like a dumbbell. The larger the value, the more the handle of the “dumbbell” long. Therefore, physicists simply use the electric dipole moment as a physical quantity to measure the “shape” of the electron. “Clouds” around the electronics It is also very simple to detect the electric dipole moment of an electron. It is only necessary to detect the behavior of the electron in the applied electric field. However, detecting the electric dipole moment of a microparticle is not that simple. Because in the quantum world, vacuum is not really empty.
Instead, it contains countless fleeting virtual particles. Some of these virtual particles may carry electric charges and have their own electric dipole moments. In this way, the virtual particles in a certain range around the electrons are like a cloud, which affects the detection value of the electric dipole moment. The best physical theory describing the microscopic particles, the standard model, considers all the virtual particles that may appear in the vacuum, and predicts the electric dipole moment of our electrons: the electric dipole moment of the electron is so small that it is so The experimental facility did not have the opportunity to measure it. But what does it mean if ACME really detects the electric dipole moment of the electron? This means that the detected value of the electric dipole moment is amplified. So what is the factor that magnifies the detected value of the electronic dipole moment? Scientists suspect that it may be that in the “cloud” around the electrons, there are unknown particles that are not predicted by some standard models. It is these unknown particles that increase the detection value of the electronic electric dipole moment. Finding unknown particles by detecting the electric dipole moment of electrons is the real goal of ACME experiments. Looking for unknown particles In particle physics, there are still many problems to be solved, such as what particles are composed of dark matter, why the whole universe is dominated by particles rather than antiparticles, and so on.
These questions are not answered by the standard model. In this regard, physicists have proposed a number of new theories, which also predict many new particles. In order to validate these new theories, we need to test whether these newly predicted particles really exist. This can be done with large experimental equipment, such as the Large Hadron Collider, which allows protons to collide at very high speeds to produce these new particles. Now we have another way: we can detect the “clouds” around the electrons and their effects on the electric moments of the electrons to find new particles. In the ACME experiment, the electric dipole moment of the electron is accurately measured. If the electric dipole moment is detected, this will prove the existence of new unknown particles, and the physicist can also introduce some properties of the unknown particle. . How to measure the electric dipole moment of an electron? We need to find a very strong electric field to test the response of an electron. This electric field can be found in molecules such as cerium oxide. The covalent bond formed between two atoms in the ruthenium oxide molecule is strong, and the generated electric field is the electric field within the strongest molecule known. Cerium oxide is the molecule used by ACME in experiments. The physicist only needs to estimate the electric dipole moment of the electron by detecting the reaction of electrons in the cerium oxide molecule. However, the experimental result is that ACME physicists did not detect the electric dipole moment of the electron, which indicates that its value is too small and cannot be detected by current experimental instruments. Nevertheless, the experimental results are still of great significance. The electric dipole moment of the electron is not detected, which directly excludes the particles predicted in many theories. The physicist can perfect the current theory or propose a new theory based on this. In addition, this result can guide us how to use the Large Hadron Collider to search for new particles.