Introduction
Particle physics is defined as a field of study involving the nature of matter at the smallest quantum scale of subatomic particles and their behavior using Fundamental interactions.
Most of the behavior of the particles at such a small scale is described by a theory known as the Standard Model of Particle Physics, which explains 3 out of 4 known Fundamental interactions in nature (Gravity not included) and classifies particles according to various characteristics. That’s why particle physics is important. Here’s a short introduction to the field.
Credit – Argonne National Laboratory. Source. License – Public Domain
Particle Physics is also known as high-energy physics because most of the subatomic particles involving particle physics don’t exist in nature in normal conditions, they are usually produced by very high energy collisions such as in particle accelerators.
Elementary particles are particles that are not composed of any other particles, whereas composite particles are particles that are composed of two or more particles. The research in Particle Physics has been found to have lots of applications in different areas of science like medical treatment.
What is the Standard Model in Particle Physics?
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The Standard Model of Particle Physics describes the behavior of subatomic particles and the three fundamental interactions, the strong force, the weak force, and the electromagnetic force using force carriers called gauge bosons.
The gauge bosons that exist in nature are the W+, W- and the Z bosons, eight gluons, photons, and the still hypothetical graviton. The Standard Model doesn’t include the fundamental force of gravity and trying to include gravity in the standard model has been unsuccessful. However since the gravity effects are negligible at the quantum scale, the predictions of the Standard Model hold very well for particle physics.
All the matter in the Universe is either made of leptons or quarks. The Standard Model got widespread acceptance in the scientific community after the experimental confirmation of the existence of quarks. Each group consists of 6 particles that are related in pairs. The lightest and most stable particles are in the first generation.
The heavier and less-stable particles belong to the second and third generations. All stable matter in the universe is made up of particles belonging to the first generation. Heavier particles quickly decay to more stable ones. The Standard Model contains 24 fundamental fermions which form matter.
There are also other unique particles such as the Higgs Boson. The Standard Model was developed in the 1970s. It is capable of explaining most of the results of particle physics experiments and phenomena. The Standard Model has become a well-established physical theory relating to the subatomic world.
What are particle accelerators and how will they help in studying Particle Physics?
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Particle accelerators are used for fundamental particle research. They utilize electromagnetic fields to shoot charged particles at extremely high speeds and energies and contain them in well-defined beams. Particle accelerators can be easily classified into two types – linear accelerators and circular accelerators.
Linear accelerators shoot particles in a straight line whereas circular accelerators accelerate particles in a circular path. Linear accelerators are mainly used in experiments where there is a fixed target whereas circular accelerators are used for both fixed target and beam-colliding experiments.
High-energy particle accelerators and detectors are used to test the predictions and limits of the Standard Model. Some of the biggest particle physics accelerators in laboratories are CERN on the French-Swiss border, Fermilab in the US, Institute of High Energy Physics in China, Brookhaven National Laboratory in the US, KEK in Japan, SLAC National Accelerator Laboratory in the US, Budker Institute of Nuclear Physics in Russia. Today there are about 30,000 particle accelerators in the world.
What are the opportunities for a Career and Research in Particle Physics?
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To get into Particle Physics, you need to have a graduate degree in Physics or Mathematics after having completed an undergraduate degree in Physics or Mathematics. Particle Physics is as hard as Physics and Math can get. Most Particle Physicists complete their doctoral degrees.
Particle Physicists can find good careers in Experimental Particle Physics facilities as well as Theoretical Particle Physics in academia. Experimental particle physicists are responsible for designing large-scale experiments which are used to solve the fundamental problems of the Universe.
Experimental Particle Physicists also analyze the data from the experiments, develop high-tech pieces of equipment for the experiments, and provide data and models for Theoretical Particle Physicists to work on.
Theoretical particle physics involves creating mathematical and analytical models to describe the creation, evolution, and behavior of subatomic particles in experiments conducted and predicting the behavior of subatomic particles in future experiments. Theoretical Particle Physicists develop advanced mathematical theories to describe the working of subatomic particles and to explain observed data via Experimental Particle Physics.
What are the major Unsolved Problems in Particle Physics?
Even though the Standard Model predicts most of the particle physics phenomena observed in laboratories it is still unable to explain some important questions about the fundamental particles and the Universe. Some of the major unsolved problems in Particle Physics and the Standard Model are given below.
The existence of Graviton
Scientists think that gravity may also be transmitted by a force carrier particle known as the Graviton. The Standard Model is incompatible with Gravity and gravity effects are negligible at the subatomic scale. The discovery of gravitational waves has made the possibility of the existence of Graviton more probable. The Standard Model cannot predict the existence of the Graviton.
The existence of Dark Matter
There is a lot of mass in galaxies that are unaccounted for. Physicists call them Dark Matter. It is still unknown what kind of subatomic particles Dark Matter is made up of. Dark matter accounts for 27% of the matter-energy content in the Universe. The Standard Model doesn’t predict the existence of Dark Matter.
The existence of Dark Energy
Earlier it was predicted that the Universe is expanding at a constant rate and the expansion rate would decrease due to the gravitational pull of the masses in the Universe. However, astronomers have found that Universe is not only expanding but is also accelerating outwards.
This accelerated expansion of the Universe is thought to have been caused by the Dark Energy content of Space-Time. Dark Energy is found to account for a whopping 68% of all matter-energy content in the Universe. Scientists have no clue what Dark Energy is and the Standard Model of Particle Physics doesn’t predict the existence of Dark Energy.
The Neutrino Mass Problem
According to the Standard Model, neutrinos shouldn’t have mass, yet scientists have discovered that the three types of neutrinos transform into one another, this can be possible only if neutrinos have mass. There is also a possibility that there is another type of undiscovered neutrino called the sterile neutrino.
The Predominance of matter over antimatter in the Universe
When energy is converted into matter, its antimatter is also formed. Accordingly, there must have been equal amounts of matter and antimatter in the Universe. However, it is found that matter is much more predominant than antimatter in the Universe, this is found to have occurred as a result of the Baryogenesis reaction that took place in the early Big Bang. The Standard Model cannot explain this observation.
The Standard Model cannot explain these observed phenomena and some other experimental and theoretical predictions.
What is your favorite aspect of Particle Physics? Comment below.
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