Elementary Particles in Standard Model
This is the standard model of elementary particles,
also known as fundamental particles.
It may look complicated at first,
but it is organized in a way which
makes it very easy to understand.
Let's take a closer look. There are two types
of particles, fermions
arranged on the left side and bosons
on the right side starting with the
bosons. Bosons are the elementary
particles with integer spin values of
either 0 or 1. They do not follow Pauli
exclusion principle and are
characterized by Bose Einstein Statistics.
Bosons are classified into
gauge bosons and scalar bosons depending
on the value of spin. Gauge Bosons have the
spin value of 1,
while scalar bosons have the spin value of zero.
Gauge Bosons are four types.
Gluons, photons, W and Z bosons.
Gluons are the exchange particles for the
strong interactions. Photons are the
exchange particles for the electromagnetic
interactions. W and Z Bosons
are the exchange particles for the weak
interactions. W Bosons have either a
positive or a negative charge. Z Bosons
have no charge and they are electrically
neutral.
Scalar boson. Higgs boson is the only
scalar boson and it is the most recent
addition to the elementary particles.
Higgs boson is a quantum excitation in the
Higgs field. Unlike other fields such as
electromagnetic field, Higgs field has a
nonzero value in vacuum. Higgs field
interacts with particles to provide
intrinsic mass. Till now we have seen
elementary particles responsible for
three out of four fundamental
interactions. The fourth fundamental
interaction, gravity does not have a boson.
At least not till now.
Graviton is a hypothetical boson
predicted to be mass less, charge less and
have a spin value of 2. If it exists it
is believed to be the exchange particles for gravity.
Even if it exists, it is very
difficult to detect a graviton as
gravity is many times weaker than other
interactions. So, we won't be seeing
graviton on the standard model for a long time.
Now moving on to Fermions,
Fermions are the elementary particles
with half integer spin values. They follow
Pauli Exclusion Principle and are
characterized by Fermi-Dirac Statistics.
Fermions are classified as quarks and
leptons, depending on the interactions
they undergo.
Quarks and leptons both are further
classified into three generations
depending on their masses. Quarks are the
fermions which experiences all four
fundamental interactions, strong
electromagnetic, weak and gravity.
The intrinsic mass of quarks comes from
interaction with Higgs field.
Individual quarks does not exist because of color
confinement. Therefore, quarks are
observed only inside composite structures
such as proton or neutron. There are six
flavors of quarks, distributed over three
generations.
Generation 1: up and down quarks are least
massive and most stable. Generation 2
charm & strength and Generation 3
top & bottom quarks are unstable and
rapidly decay into up
and down quarks. Higher generation
massive quarks are
produced during high-energy
collisions involving cosmic rays or
inside particle accelerators.
Leptons are the fermions which
experiences only three out of four
fundamental interactions.
Unlike quarks, leptons don't experience
strong interactions and hence they are
not bound by color confinement.
Therfore, they can exist freely in isolation.
The intrinsic mass of leptons comes from
interaction with Higgs field. Like quarks,
there are six flavors of leptons
distributed over three generations.
Generation 1: electron and electron
neutrino are least massive and most
stable. Generation 2: muon & muon neutrino
and Generations 3: tau and
tau neutrino are unstable and rapidly
decay into electron and electron neutrino.
Higher generation massive
leptons are produced during high-energy
collisions involving cosmic rays or
inside particle accelerators.
At last there are antiparticles. Only fermions
have antiparticles. Bosons either
don't have antiparticles or they are
their own antiparticles. Antiparticles of
quarks are called antiquarks.
Antiparticles of leptons are called
antileptons.
We have seen all the elementary particles
of the standard model.
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