Modern Physics

Standard Model of Particle Physics

The Standard Model of Particle Physics predicts the existence of 17 elementary particles.

The Standard Model of Particle Physics is divided into bosons, quarks and leptons
The Standard Model is the name given to a physical theory from the 1970s that describes elementary particles and the way they interact with each other. This model incorporates all known subatomic particles and its most recent addition took place in 2012, with experimental confirmation of the existence of the Higgs boson . Altogether, the Standard Model considers the existence of 17 fundamental particles, divided into three categories: bosons , quarks and leptons . Together they give rise to matter and all kinds of interactions in the Universe. In addition, quarks and leptons also exist in nature in the form of antiparticles, fundamentally presenting an inverted electrical charge signal in relation to the original matter. The Standard Model can be divided into two groups of particles, fermions and bosons.


Basically they are the “bricks” that make up matter. Fermions are particles that have a quantum property called spin (a kind of quantum angular momentum) of semi – integer modulus (½), being described by the Pauli Exclusion principle . In other words, two fermions at the same energy level cannot have the same quantum numbers or occupy the same position in space at the same time .

The “lighter” (less massive) fermions are called leptons (Greek: “light”), and the heavier ones, such as protons, neutrons and atoms, formed by states of quarks bound by the strong interaction , are called hadrons (Greek for “strong”). Trios of quarks are called baryons (protons and neutrons), and pairs of quarks are called mesons .


Bosons are the particles responsible for the interaction between fermions. Unlike them, these particles have no problem occupying the same place in space at the same time . They have integer spin , have no mass and can have an electrical charge . Bosons are the gluons, photons, W and Z bosons, and the Higgs boson. Each of them is responsible for the mediation of a type of force of nature. Photons, for example, are responsible for electromagnetic interaction. Due to its properties, it is possible for a beam of light to pass through another without any collision between them.

Gluons, in turn, are the mediators of the strong interaction , which holds quarks together, forming mesons and baryons. The W and Z bosons are responsible for the electroweak force , common in beta decays . The Higgs boson, in turn, is the particle responsible for attributing mass to fermions.

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