The Standard Model(표준모형)

<written on 2019.11.23>

Over time, scientists have tried to hack matter into smaller pieces, to find what the world is made out of. Empedokles(490~430 B.C.) first thought that everything in the world were combinations of 4 things: fire, water, air, and soil. That idea has been accepted for centuries, until Democritus thought of atoms, the most elementary matter that could not be broken. After that, people found out that atoms were made out of even smaller particles; electrons, protons, and neutrons. Now, the standard model is widely accepted.

https://www.facebook.com/cern/photos

What is the Standard model?

The standard model suggests that even protons and neutrons can be separated into much smaller particles, called quarks. In the model, there are particles that carry different types of forces, too.

Particles in the standard model can be divided into three groups. Quarks join together to form hadrons, which are matter such as protons and neutrons. Leptons have small mass, and a negative charge. Electrons are part of the lepton group. Quarks and leptons are both in a group called fermions, which are matter particles. Bosons, on the other hand, are particles that carry force, or give matters their mass. 

 

Quarks

Quarks	1st generation	2nd generation	3rd generation
positive charge(+2/3)	up quark  - 2.2 MeV/c^2	charm quark  - 1.28 GeV/c^2	top quark  - 173.1 GeV/c^2
negative charge(-1/3)	down quark  - 4.7 MeV/c^2	strange quark  - 96 MeV/c^2	bottom quark  - 4.18 GeV/c^2

Out of the 6 types of quarks, 3 of them have a positive charge of +2/3, and the rest have a negative charge of -1/3. Every quarks have have half spins(1/2).There are three generations of quarks, but most hadrons in the world are made of quarks of the first generation. It is because the masses of the second and third generation is large; they eventually decay into quarks of the first generation.  Hadrons are formed by different formations of quarks. for example, a proton is made of two positive up quarks and a negative down quark. All three quarks in a hadron need to have different 'colors' in order to stick together. Quarks are affected by all types of forces in the universe.

https://en.wikipedia.org/wiki/Quark

Leptons

Leptons	1st generation        (electronic leptons)	2nd generation          (muonic leptons)	3rd generation              (tauonic leptons)
leptons(-1)	electron  - 0.511 MeV/c2	muon  - 105.66 MeV/c^2	tau  - 1.7768 GeV/c^2
neutrinos(0)	electron neutrino  - 1.0 eV/c^2	muon neutrino  - 0.17 MeV/c^2	tau neutrino  - 18.2 MeV/c^2

There are also three generations of leptons, increasing in mass. Higher-mass particles such as muon and tau can be created in high energy stuations such as cosmic rays or in particle accelerators, but they decay easily. Neutrinos have very small masses, and have no charge; therefore they do not interact with other particles very much.

Gauge Bosons(Vector Bosons)

Force	electromagnetivity	strong force	weak force	gravity
Bosons	photon	gluon	Z,+W,-W	graviton(unfound)

Vector bosons are force-carriers. Photons, or particles of light, carry electromagnetivity. Its rest mass and charge are both 0, and the spin is 1. That the rest mass is 0 doesn't mean that it does not exist. Instead, photons cannot 'rest'; they are constantly moving. The physical quantities are the same for gluons, too. The Z boson, +W boson, and the -W boson all carry weak force. Z bosons have a mass of 91.19 GeV/c^2, and its spin is 1. Both types of W bosons(+1 charge and -1 charge) have a mass of 80.39 GeV/c^2, and their spin is also 1.

Scalar Bosons

There is only one scalar boson known so far. It is the higgs boson, also known as 'God's Particle'. The name was given beacsue it gives the most fundamental physical quantity to other particles: mass. Mass is the measurement of inertia, and the field of higgs is what give objects inertia. The higgs boson's mass is 124.97 GeV/c^2. Its charge and spin are both 0.