Elementary particles #SciChallenge2017

1. ELEMETARY
PARTICLES
BARİS
BAYRAKTAR

2. WHAT IS THE ELEMENTARY PARTICLE?
Elementary particles are insight into the fundamental structure of matter. Elementary
particles examined in two fundamental groups: fermions and bosons.
Elementary
particles
Fermions
Half-integer spin
Obey the Pauli exclusion principle
Quarks and antiquarks
Have color charge
Participate in strong interactions
Generations
1. Up (u)
2. Down (d)
3. Charm (c)
4. Strange (s)
5. Top (t)
6. Bottom (b)
Leptons and antileptons
No color charge
Electroweak interactions
Generations
1. Electron (e−), Electron neutrino (νe)
2.Muon (μ−), Muon neutrino (νμ)
3.Tau (τ−), Tau neutrino (ντ)
The antielectron (e+) is traditionally called
positron.
Bosons
Integer spin
Obey the Bose–Einstein statistics
Gauge bosons
Spin ≠ 0
Force carriers
Four kinds (four fundamental interactions)
1. Photon (γ, Electromagnetic interaction)
2. W and Z bosons (W+, W−, Z, weak
interaction)
3. Eight types of gluons (g, strong
interaction)
4. Graviton (G, gravity, hypothetical)
Scalar bosons
Spin = 0
Higgs boson

3. The Standard Model of particle physics is the theory
describing three of the four known fundamental forces in the
universe (the electromagnetic, weak, and strong
interactions), as well as classifying all known elementary
particles. It was developed in stages throughout the latter
half of the 20th century, through the work of many scientists
around the World, with the current formulation being
finalized in the mid-1970s upon experimental confirmation of
the existence of quarks. Since then, confirmation of the top
quark (1995), the tau neutrino (2000), and the Higgs boson
(2012) have added further credence to the Standard Model.
In addition, the Standard Model has predicted various
properties of weak neutral currents and the W and Z bosons
with great accuracy.
Although the Standard Model is believed to be theoretically
self-consistent and has demonstrated huge successes in
providing experimental predictions, it leaves some
phenomena unexplained and falls short of being a complete
theory of fundamental interactions. It does not fully explain
Baryon asymmetry, incorporate the full theory of gravitation
as described by general relativity, or account for the
accelerating expansion of the Universe as possibly described
by dark energy. The model does not contain any viable dark
matter particle that possesses all of the required properties
deduced from observational cosmology. It also does not
incorporate neutrino oscillations and their non-zero masses.

4. The development of the Standard
Model was driven by theoretical and
experimental particle physicists alike.
For theorists, the Standard Model is a
paradigm of a quantum field theory,
which exhibits a wide range of physics
including spontaneous symmetry
breaking, anomalies and non-
perturbative behavior. It is used as a
basis for building more exotic models
that incorporate hypothetical
particles, extra dimensions, and
elaborate symmetries (such as
supersymmetry) in an attempt to
explain experimental results at
variance with the Standard Model,
such as the existence of dark matter
and neutrino oscillations.

5. FERMIONS
In particle physics, a fermion (a
name coined by Paul Dirac from
the surname of Enrico Fermi) is
any subatomic particle
characterized by Fermi–Dirac
statistics. These particles obey the
Pauli exclusion principle. Fermions
include all quarks and leptons, as
well as any composite particle
made of an odd number of these,
such as all baryons and many
atoms and nuclei. Fermions differ
from bosons, which obey Bose–
Einstein statistics.

6. QUARKS
A quark is an elementary particle and a fundamental constituent of matter.
Color-charged particles may combine to form
color neutral composite particles called hadrons.
A quark may pair up with an antiquark: the quark
has a color and the antiquark has the
corresponding anticolor. The color and anticolor
cancel out, forming a color neutral meson.
Alternatively, three quarks can exist together, one
quark being "red", another "blue", another
"green". These three colored quarks together
form a color-neutral baryon. Symmetrically, three
antiquarks with the colors "antired", "antiblue"
and "antigreen" can form a color-neutral
antibaryon.
Quarks also carry fractional electric charges, but,
since they are confined within hadrons whose
charges are all integral, fractional charges have
never been isolated. Note that quarks have
electric charges of either + 2⁄3 or − 1⁄3, whereas
antiquarks have corresponding electric charges of
either − 2⁄3 or + 1⁄3.

7. Gluons

8. The remaining six fermions do
not carry colour charge and are
called leptons. The three
neutrinos do not carry electric
charge either, so their motion is
directly influenced only by the
weak nuclear force, which makes
them notoriously difficult to
detect. However, by virtue of
carrying an electric charge, the
electron, muon, and tau all
interact electromagnetically.

9. Each member of a generation has greater
mass than the corresponding particles of
lower generations. The first generation
charged particles do not decay; hence all
ordinary (baryonic) matter is made of such
particles. Specifically, all atoms consist of
electrons orbiting around atomic nuclei,
ultimately constituted of up and down
quarks. Second and third generation
charged particles, on the other hand, decay
with very short half lives, and are observed
only in very high-energy environments.
Neutrinos of all generations also do not
decay, and pervade the universe, but rarely
interact with baryonic matter.
A lepton is half-integer spin (spin 1⁄2)
particle that does not undergo strong
interactions. Two main classes of leptons
exist: charged leptons (also known as the
electron-like leptons), and neutral leptons
(better known as neutrinos). Charged
leptons can combine with other particles to
form various composite particles such as
atoms and positronium, while neutrinos
rarely interact with anything, and are
consequently rarely observed.

10. Electron-neutrinos are
produced in unimaginable
numbers during supernova
explosions and it is these
particles that disperse
elements produced by
nuclear burning into the
universe. These elements
include the carbon from
which we are made, the
oxygen we breathe, and
almost everything else on
earth. Therefore, in spite of
the reluctance of neutrinos
to interact with other
fundamental particles, they
are vital for our existence.
The other two neutrino
pairs (called muon and
muon neutrino, tau and tau
neutrino) appear to be just
heavier versions of the
electron.
Supernova

11. Fundamental Forces
Matter is effected by forces or interactions (the terms are interchangeable). There
are four fundamental forces in the universe:
• Gravitation (between particles with mass)
• Electromagnetic (between particles with charge/magnetism)
• Strong nuclear force (between quarks)
• Weak nuclear force (operates between neutrinos and electrons)
The first two you are familiar with, gravity is the attractive force between all
matter, electromagnetic force describes the interaction of charged particles and
magnetics. Light (photons) is explained by the interaction of electric and magnetic
fields.

12. The strong force binds quarks into protons, neutrons and mesons, and holds the nucleus of
the atom together despite the repulsive electromagnetic force between protons. The weak
force controls the radioactive decay of atomic nuclei and the reactions between leptons
(electrons and neutrinos).
Current physics (called quantum field theory) explains the exchange of energy in interactions
by the use of force carriers, called bosons. The long range forces have zero mass force
carriers, the graviton and the photon. These operate on scales larger than the solar system.
Short range forces have very massive force carriers, the W+, W- and Z for the weak force, the
gluon for the strong force. These operate on scales the size of atomic nuclei.
So, although the strong force has the greatest strength, it also has the shortest range.

13. Interactions in physics are the ways that
particles influence other particles. At a
macroscopic level, electromagnetism allows
particles to interact with one another via
electric and magnetic fields, and gravitation
allows particles with mass to attract one
another in accordance with Einstein's
theory of general relativity. The Standard
Model explains such forces as resulting
from matter particles exchanging other
particles, generally referred to as force
mediating particles. When a force-
mediating particle is exchanged, at a
macroscopic level the effect is equivalent to
a force influencing both of them, and the
particle is therefore said to have mediated
(i.e., been the agent of) that force. The
Feynman diagram calculations, which are a
graphical representation of the
perturbation theory approximation, invoke
"force mediating particles", and when
applied to analyze high-energy scattering
experiments are in reasonable agreement
with the data. However, perturbation
theory (and with it the concept of a "force-
mediating particle") fails in other situations.
These include low-energy quantum
chromodynamics, bound states, and
solitons.

14. Grand unification theories
The Georgi-Glashow model predicts additional gauge bosons named X and Y
bosons. The hypothetical X and Y bosons direct interactions between quarks and
leptons, hence violating conservation of baryon number and causing proton
decay. Such bosons would be even more massive than W and Z bosons due to
symmetry breaking. Analysis of data collected from such sources as the Super-
Kamiokande neutrino detector has yielded no evidence of X and Y bosons.
Gravitons
The fourth fundamental interaction, gravity, may also be carried by a boson,
called the graviton. In the absence of experimental evidence and a
mathematically coherent theory of quantum gravity, it is unknown whether this
would be a gauge boson or not. The role of gauge invariance in general relativity
is played by a similar symmetry: diffeomorphism invariance.
W' and Z' bosons
W' and Z' bosons refer to hypothetical new gauge bosons (named in analogy with
the Standard Model W and Z bosons). There are three weak gauge bosons: W+,
W−, and Z0; these mediate the weak interaction.
Gluons
Gluons mediate the strong interaction, which join quarks and thereby form hadrons,
which are either baryons (three quarks) or mesons (one quark and one antiquark).
Protons and neutrons are baryons, joined by gluons to form the atomic nucleus. Like
quarks, gluons exhibit colour and anticolour—unrelated to the concept of visual
color—sometimes in combinations, altogether eight variations of gluons.

15. The Higgs boson is an elementary particle
in the Standard Model of particle physics. It
is the quantum excitation of the Higgs field,
a fundamental field of crucial importance
to particle physics theory first suspected to
exist in the 1960s. Unlike other known
fields such as the electromagnetic field, it
has a non-zero constant value in vacuum.
The question of the Higgs field's existence
became the last unverified part of the
Standard Model of particle physics, and for
several decades was considered "the
central problem in particle physics".
Higgs Boson

16. The Higgs field is believed to permeate the entire Universe, proving its existence
was far from easy. In principle, it can be proved to exist by detecting its excitations,
which manifest as Higgs particles (the 'Higgs boson'), but these are extremely
difficult to produce and to detect. The importance of this fundamental question led
to a 40 year search, and the construction of one of the world's most expensive and
complex experimental facilities to date, CERN's Large Hadron Collider, in an attempt
to create Higgs bosons and other particles for observation and study. On 4 July
2012, the discovery of a new particle with a mass between 125 and 127 GeV/c2 was
announced; physicists suspected that it was the Higgs boson. Since then, the
particle has been shown to behave, interact, and decay in many of the ways
predicted for Higgs particles by the Standard Model, as well as having even parity
and zero spin, two fundamental attributes of a Higgs boson. This also means it is the
first elementary scalar particle discovered in nature. More studies are needed to
verify with higher precision that the discovered particle has properties matching
those predicted for the Higgs boson by the Standard Model, or whether, as
predicted by some theories, multiple Higgs bosons exist.
Physicists explain the properties and forces between elementary particles in terms of
the Standard Model—a widely accepted and "remarkably" accurate framework for
understanding almost everything in the known universe, other than gravity. In this
model, the fundamental forces in nature arise from properties of our universe called
gauge invariance and symmetries. The forces themselves are transmitted by particles
known as gauge bosons.

17. Supersymmetry extends the Standard Model by adding another class of symmetries to
the Lagrangian. These symmetries exchange fermionic particles with bosonic ones. Such
a symmetry predicts the existence of supersymmetric particles, abbreviated as
sparticles, which include the sleptons, squarks, neutralinos, and charginos. Each particle
in the Standard Model would have a superpartner whose spin differs by 1⁄2 from the
ordinary particle. Due to the breaking of supersymmetry, the sparticles are much heavier
than their ordinary counterparts; they are so heavy that existing particle colliders would
not be powerful enough to produce them. However, some physicists believe that
sparticles will be detected by the Large Hadron Collider at CERN.

18. String theory is a model of physics where all "particles" that
make up matter are composed of strings (measuring at the
Planck length) that exist in an 11-dimensional (according to M-
theory, the leading version) or 12-dimensional (according to F-
theory[17]) universe. These strings vibrate at different
frequencies that determine mass, electric charge, color charge,
and spin. A string can be open (a line) or closed in a loop (a
one-dimensional sphere, like a circle). As a string moves
through space it sweeps out something called a world sheet.
String theory predicts 1- to 10-branes (a 1-brane being a string
and a 10-brane being a 10-dimensional object) that prevent
tears in the "fabric" of space using the uncertainty principle
(e.g., the electron orbiting a hydrogen atom has the probability,
albeit small, that it could be anywhere else in the universe at
any given moment).
String theory proposes that our universe is merely a 4-brane,
inside which exist the 3 space dimensions and the 1 time
dimension that we observe. The remaining 6 theoretical
dimensions either are very tiny and curled up (and too small to
be macroscopically accessible) or simply do not/cannot exist in
our universe (because they exist in a grander scheme called the
"multiverse" outside our known universe).
Some predictions of the string theory include existence of
extremely massive counterparts of ordinary particles due to
vibrational excitations of the fundamental string and existence
of a massless spin-2 particle behaving like the graviton.

19. According to preon theory there are
one or more orders of particles
more fundamental than those (or
most of those) found in the
Standard Model. The most
fundamental of these are normally
called preons, which is derived from
"pre-quarks". In essence, preon
theory tries to do for the Standard
Model what the Standard Model did
for the particle zoo that came before
it. Most models assume that almost
everything in the Standard Model
can be explained in terms of three
to half a dozen more fundamental
particles and the rules that govern
their interactions. Interest in preons
has waned since the simplest
models were experimentally ruled
out in the 1980s.

20. • https://en.wikipedia.org/wiki/Elementary_particle
• https://home.cern/about/physics/standard-model
• https://en.wikipedia.org/wiki/Standard_Model
• https://en.wikipedia.org/wiki/Fermion
• https://en.wikipedia.org/wiki/Quark
• https://en.wikipedia.org/wiki/Lepton
• http://abyss.uoregon.edu/~js/ast123/lectures/lec07.html
• http://www.iflscience.com/physics/what-are-fundamental-particles/
• https://en.wikipedia.org/wiki/Higgs_boson
• https://en.wikipedia.org/wiki/Gauge_boson