Particle physics (also high energy physics) is a branch of physics that studies the nature of the particles that constitute matter and radiation. 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 fundamental interactions necessary to explain their behaviour. 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.[1][2]