Language
Country/Area
No result found
The wonderful world of elementary particles: Does our universe really only have 61 kinds of particles?
Particle physics is the study of the elementary particles that make up matter and radiation and their interactions. This field includes not only the study of elementary particles, but also the matter that is composed of elementary particles, such as protons and neutrons. According to the standard model, the fundamental particles in the universe are divided into fermions (matter particles) and bosons (particles that transmit force). Although there are three generations of fermions in the universe, the ordinary matter we come into contact with in our daily lives is composed only of first-generation fermions, namely up quarks and down quarks, electrons and electron neutrinos.
The fundamental particles interact with each other in complex ways, mediated by bosons, including the electromagnetic force, the weak force, and the strong force.
Interestingly, quarks cannot exist independently, but rather in the form of hadrons; particles with an odd number of quarks in a hadron are called baryons, while particles with an even number of quarks are called mesons. Protons and neutrons are primarily made up of baryons and make up the vast majority of our everyday matter. Compared to protons and neutrons, muons are unstable and exist for only a few microseconds.
Every particle has a corresponding antiparticle, which has the same mass as the particle but the opposite charge. For example, the antiparticle of the electron is the positron. This means that the existence of antiparticles and antimatter is theoretically possible.
Related research shows that the interaction between particles and antiparticles can lead to their annihilation and transformation into other particles, which further verifies the complexity of matter.
For some particles, such as photons, they are their own antiparticles. These elementary particles are actually excited states of quantum fields, which are responsible for the interactions between particles. The Standard Model is the mainstream theory that explains these elementary particles and their interactions. How to integrate gravity with existing particle physics theories remains an unsolved problem. Many theories such as loop quantum gravity, string theory and supersymmetry theory have been proposed to solve this problem.
Historical BackgroundThe idea that matter is made up of elementary particles dates back to the 6th century BC. By the 19th century, John Dalton, through his work in stoichiometry, concluded that every element in nature was made up of a unique type of particle. Subsequent research showed that atoms are not the most basic particles of matter, but are composed of smaller particles (such as electrons).
After entering the 20th century, the exploration of nuclear physics and quantum physics led to the discovery of nuclear fission and nuclear fusion in 1939, which not only triggered the development of nuclear weapons but also promoted the development of modern particle physics.
Throughout the 1950s and 1960s, various particles were discovered in high-energy collisions, a phenomenon known as the "particle zoo," which inspired physicists to think about new problems related to the imbalance of matter and antimatter.
After the proposal of the Standard Model, physicists revealed that this insane "particle zoo" was formed by the combination of a few fundamental particles, marking the beginning of modern particle physics.
Introduction to the Standard Model
The current classification of all elementary particles is primarily explained by the Standard Model, which gained widespread acceptance and experimental confirmation in the mid-1970s. The Standard Model describes the three fundamental interactions, strong, weak and electromagnetic, and uses mediating bosons to explain them, including eight gluons, the W−, W+ and Z bosons, and the photon. The Standard Model also includes 24 fundamental fermions (12 particles and their antiparticles) that constitute the basic building blocks of all matter.
The Standard Model also predicts the existence of the Higgs boson. On July 4, 2012, physicists from CERN's Large Hadron Collider announced that they had discovered a new particle that behaves like the Higgs boson. The current Standard Model has 61 fundamental particles that can combine to form composite particles, which also explains the hundreds of other particles discovered since the 1960s.
Although the Standard Model has shown high consistency in nearly all experimental tests, most particle physicists believe that its description of nature is incomplete and that a more complete theory is yet to be discovered. Recent neutrino mass measurements have led to the first deviation from the Standard Model, in which neutrinos have no mass.Future Outlook
Major future efforts include searches for physics beyond the Standard Model, such as the Future Circular Collider proposed by CERN, and recommendations from the US Particle Physics Prioritization Panel (P5), which will update the 2014 P5 study. The report recommends several experimental projects, including the deep underground neutrino experiment.
The interactions between various particles make our universe full of unknowns and surprises. But how many undiscovered particles and interactions are hidden in this infinite and profound world of particles?
