|Topical Notes, Problems, Presentations, Quiz, Test, Investigations and Videos|
|7.1. Discrete energy and radioactivity|
|7.2. Nuclear reactions|
|7.3. The structure of matter|
Particle physics (also high energy physics) is the branch of physics that studies the nature of the particles that constitute matter(particles with mass) and radiation (massless particles). Although the word “particle” can refer to various types of very small objects (e.g. protons, gas particles, or even household dust), “particle physics” usually investigates the irreducibly smallest detectable particles and the irreducibly fundamental force fields necessary to explain them. By our current understanding, these elementary particles are excitations of the quantum fields that also govern their interactions. The currently dominant theory explaining these fundamental particles and fields, along with their dynamics, is called the Standard Model. Thus, modern particle physics generally investigates the Standard Model and its various possible extensions, e.g. to the newest “known” particle, the Higgs boson, or even to the oldest known force field, gravity.
Modern particle physics research is focused onsubatomic particles, including atomic constituents such as electrons, protons, and neutrons (protons and neutrons are composite particles calledbaryons, made of quarks), produced byradioactive and scattering processes, such asphotons, neutrinos, and muons, as well as a wide range of exotic particles. Dynamics of particles is also governed by quantum mechanics; they exhibit wave–particle duality, displaying particle-like behaviour under certain experimental conditions and wave-like behaviour in others. In more technical terms, they are described byquantum state vectors in a Hilbert space, which is also treated in quantum field theory