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Pauli exclusion principle no two identical fermions (particles
with half- integer spin) may occupy the same quantum state
simultaneously. Back
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Bosons Unlike fermions, bosons do not follow the Pauli
exclusion principle, which makes them perfect for the job as force
carriers. Explore more bosons Go back What is the Pauli Exclusion
principle
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Standard Model Bosons Fermions
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Do not cheat ! Use only your mouse Mr. Crow is watching
you
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Standard Model However, the Standard Model falls short of being
a complete theory of fundamental interactions because it does not
incorporate the physics of dark energy nor of the full theory of
gravitation as described by general relativity. The theory does not
contain any viable dark matter particle that possesses all of the
required properties deduced from observational cosmology. It also
does not correctly account for neutrino oscillations (and their
non-zero masses). The Standard Model of particle physics, which was
developed throughout the mid to late 20th century, is a theory
concerning the electromagnetic, weak, and strong nuclear
interactions, which mediate the dynamics of the known subatomic
particles. Since then, discoveries of the bottom quark (1977), the
top quark (1995) and the tau neutrino (2000) have given further
evidence that the Standard Model is accurate theory. Lets
Start
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Boson Family Z boson W bosons gluon Graviton Higgs boson
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Higgs Boson The Higgs boson is a hypothetical elementary
particle predicted by the Standard Model of particle physics. The
Standard Model predicts the existence of a field (called the Higgs
field) which has a non-zero amplitude in its ground state. The
field can be pictured as a pool of molasses where Higgs bosons
"stick" to the otherwise massless fundamental particles that travel
through the field, converting them into particles with mass that
form the components of atoms. As of December 2011, the Higgs boson
has yet to be confirmed experimentally, despite large efforts
invested in accelerator experiments at CERN and Fermilab. Like
other massive particles (e.g. the top quark and W and Z bosons),
Higgs bosons created in particle accelerators decay long before
they reach any of the detectors. However, the Standard Model
precisely predicts the possible modes of decay and their
probabilities. This allows events in which a Higgs was created to
be identified by examining the decay products. Back
Slide 9
The W and Z bosons (together known as the weak bosons) are the
elementary particles that mediate the weak interaction; their
symbols are W +, W , and Z. Weak Bosons These bosons are among the
heavyweights of the elementary particles. With masses of 80.4
GeV/c2 and 91.2 GeV/c2, respectively, the W and Z bosons are almost
100 times as massive as the proton - heavier, even, than entire
atoms of iron. (This does not mean they are bigger than iron atoms.
They still have zero size, but with lots of mass.) The masses of
these bosons are significant because they act as the force carriers
of the weak force, and the high mass thus limits the range. By way
of contrast, the electromagnetic force has an infinite range
because its force carrier, the photon, has zero rest mass; and the
same is supposed of the hypothetical graviton. The emission of a W
+ or W boson either raises or lowers the electric charge of the
emitting particle by one unit, and also alters the spin by one
unit. The neutral Z boson obviously cannot change the electric
charge of any particle, nor can it change any other of the
so-called "charges" (such as strangeness, color, charm, etc.). The
emission or absorption of a Z boson can only change the spin,
momentum, and energy of the other particle. Back
Slide 10
The photon is a quantum of light and all other forms of EM
radiation, and the force carrier for the EM force. The photon is
currently understood to be strictly massless, but if the photon is
not a massless particle, it would not move at the exact speed of
light in vacuum, c. Its speed would be lower and depend on its
frequency. Relativity would be unaffected by this; the so-called
speed of light, c, would then not be the actual speed at which
light moves, but a constant of nature which is the maximum speed
that any object could theoretically attain in space-time. Thus, it
would still be the speed of space-time ripples (gravitational waves
and gravitons), but it would not be the speed of photons. Because
the photon is thought to have zero rest mass, the electromagnetic
force has an infinite range Speed = c Back
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+ Gluons are elementary particles which act as the exchange
particles for the strong force between quarks. There are eight
independent types of gluons. Quarks carry three types of color
charge; antiquarks carry three types of anticolor charge. Gluons
may be thought of as carrying both color and anticolor. QCD
considers there to be eight gluons of the possible nine
color-anticolor combinations. The expulsion or absorption of gluons
causes a color change in quarks. Back
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The Mysterious: Graviton In physics, the graviton is a
hypothetical elementary particle that mediates the force of
gravitation in the framework of quantum field theory. If it exists,
the graviton must be massless, because the gravitational force has
unlimited range, and must be a spin 2 boson. Attempts to extend the
Standard Model or other quantum field theories by adding gravitons
run into serious theoretical difficulties at high energies. When
calculating the probability that a particle will emit or absorb a
graviton, the solutions give nonsensical answers. Since classical
general relativity and quantum mechanics seem to be incompatible at
such energies, from a theoretical point of gravity cannot be
explained. One possible solution is to replace particles by
strings. However, string theories cannot be disproved at the
current time, and therefore may not count as real theories.
Back
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A fermion can be an elementary particle, such as the electron;
or it can be a composite particle, such as the proton In contrast
to bosons, only one fermion can occupy a particular quantum state
at any given time (they follow the Pauli exclusion principle). If
more than one fermion occupies the same physical space, at least
one property of each fermion, such as its spin, must be different.
Fermions are usually associated with matter. Back HadronsLeptons
Fermions experience all four fundamental forces
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Lepton family tree electron muon tau electron neutrino muon
neutrino tau neutrino Leptons differ from their fermion brothers
(the quarks) because leptons are not involved in the strong force
Back
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Electron e-e- The electron is a subatomic particle with a
negative elementary electric charge. Electrons have the lowest mass
of any charged lepton (or electrically charged particle of any
type) and belong to the first-generation of fundamental particles.
The second and third generation contain charged leptons, the muon
and the tau, which are identical to the electron in charge, spin
and interactions, but are more massive. Unlike the muon and tau,
the electron is thought to be stable on theoretical grounds: the
electron is the least massive particle with non-zero electric
charge, so its decay would violate charge conservation. If it did
decay, the experimental lower bound for the electron's mean
lifetime is 4.610 26 years Back
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Muon The muon is an unstable subatomic particle with a mean
lifetime of 2.2 s. This lifetime is comparatively long (the second
longest known) and is due to being mediated by the weak
interaction. Muons have a mass of 105.7 MeV/c2, which is about 200
times the mass of an electron. Since the muon's interactions are
very similar to those of the electron, a muon can be thought of as
a much heavier version of the electron. Due to their greater mass,
muons are not as sharply accelerated when they encounter
electromagnetic fields, and do not emit as much radiation. The muon
was the first elementary particle discovered that does not appear
in ordinary atoms. Muons can, however, form muonic atoms (also
called mu-mesic atoms), by replacing an electron in ordinary atoms
Back
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Tau Tau leptons have a lifetime of 2.910 13 s and a mass of
1,777 MeV/c 2 The tau was detected in a series of experiments
between 1974 and 1977 by Martin Lewis Perl with his colleagues at
the SLAC-LBL group. The tau is the only lepton that can decay into
hadronsthe other leptons do not have the necessary mass. Back
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The Neutrinos The neutrino (meaning "small neutral one" in
Italian) is denoted by the Greek letter . All evidence suggests
that neutrinos have mass but that their mass is tiny even by the
standards of subatomic particles. Their mass has never been
measured accurately. Most neutrinos passing through the Earth
emanate from the Sun. About 65 billion (6.51010) solar neutrinos
per second pass through every square centimeter. Neutrinos cannot
be detected directly, because they do not ionize the materials they
are passing through because they do not carry an electric charge.
Because they are neutral particles, antineutrinos and neutrinos may
actually be the same particle. So far, there is no detection method
for low energy neutrinos that can be uniquely distinguished from
other causes. Neutrino detectors are often built underground in
order to isolate the detector from cosmic ray and other background
radiation. Back
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Hadrons Made out of 100% quality quarks and antiquarks A hadron
is a composite particle made of quarks and held together by the
strong force. Hadrons are categorized into two families: baryons
(made of three quarks) and mesons (made of one quark and one
antiquark). Quarks ->
