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Quantum Mechanics and the Standard Model

Dr Kate Lancaster introduces the principles of quantum mechanics and the standard model of particle physics.
Welcome back for week 3 of the course. Last week we explored the world of materials and nanostructures – this week, we’re zooming into the physical world even more. In this final section of the course, we will dive into quantum physics, from the Standard Model of particle physics to applications of quantum phenomena. In the world around us, we see waves, like water waves or sound waves; and we see particles, lumps of stuff, like snooker balls and cars. In the quantum world we find that things aren’t so simple. Particles, like electrons and protons, behave as if they were waves, with their own wavelengths and frequencies and wave behaviour.
And we usually think of light as a wave – the frequency of a light wave tells us its colour. But in the quantum world, light also behaves like a bunch of particles. These particles are known as photons which are tiny packets, or quanta, of energy. Which is why we call it quantum physics. When these quanta interact with each other they behave like particles and we will explore these interactions much further during this week. On the other hand, the wave-nature of these quanta is critical if we want to understand how they travel and evolve. You can also create new matter from energy or gain energy if you can make matter disappear. This is because of the relationship between energy
and mass: E = mc2. Since c, the speed of light, is really big these are either enormous energies or tiny masses. In quantum physics the most fundamental model of particles is the Standard Model. This model explains how we are made from quarks, which congregate into the protons and neutrons that form our atomic nuclei. These nuclei are responsible for almost all of our mass. The electron is also such a standard model particle, and they are responsible for the atomic structure and make up most of the volume of the atoms. The standard model explains how quarks, electrons, and other, almost invisible particles called neutrinos, interact with each other, using the so-called interaction bosons.
In fact the photon (or particle of light) is one of these interaction bosons. The electron and neutrino, and the quarks that make up our protons and neutrons, aren’t the only matter particles. In the Standard Model, we find three layers, or generations, of particles, each more massive than the ones before. Because studying larger masses requires more and more energy, we study these heavy particles using high-energy accelerators, such as in big detectors at the Large Hadron Collider at CERN. This week we will explore the zoo of particles in the Standard Model, and learn how particle detectors can help us understand and use these fundamental particles to learn about the universe, and to create new innovative technologies.

This week we will be exploring the quantum world and delving into the realm of particle physics.

We will start by investigating quantum phenomena. As Kate explains in the video above, in quantum physics particles (like electrons) can behave like waves and waves (such as light) can behave as particles. Depending on the situation, sometimes the particle nature will be visible and sometimes the wave nature will be visible. However, both parts are equally real and significant. We refer to this as wave-particle duality. We briefly encountered this topic last week when we learned about electron microscopy. This week, we will explore the implications of wave-particle duality as our first topic.

We will then look at particles in more detail. We are already familiar with the atom in which positive protons and neutral neutrons make up nuclei, surrounded by negative electrons. However, whilst electrons are considered to be a fundamental particle, protons and neutrons are made of particles called quarks. These are just one of the classes of particle in the Standard Model, which does much more than just describe the building blocks of atoms: it describes all of the fundamental particles we know.

We’ll then apply our understanding of quantum and particle physics to look at advances in medical technologies, before finishing the week with the exciting discovery of a new particle, the d* hexaquark, that might have big implications for our understanding of the universe.

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Frontier Physics, Future Technologies

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