particle physics with sanjay 630mod2
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Particle physics is the study of what everything is made of
Particle Physicists study the fundamental particles that
make up all of matter, and how they
interact with each other.
Everything around us is made up of these fundamental
building blocks of nature.
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In the early
1900's it was believed
that atoms were
fundamental;
they were thought to
be the smallest part of
nature and
were not made up of
anything smaller
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Soon thereafter, experiments were done to see if this truly
was the case. It was discovered that atoms were notfundamental at all, but were made up of two components:
a positively charged nucleus surrounded by a cloud of
negative electrons.
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Then the nucleus was probed to see if
it was fundamental, but it too was discoveredto be made up of something smaller; positive
protons and neutral neutrons bound together
with the cloud of electrons
still surrounding it.
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After that these protons and
neutrons were found it was time tosee if they were fundamental. It was
discovered that they were made up
of smaller particles called "quarks",
which today are believed to be truly
fundamental, along with electrons.Furthermore, electrons belong to a
family of fundamental particles,
which are called "leptons". Quarks
and leptons, along with the forces
that allow them to interact, arearranged in a nice neat theory named
the standard model
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The Standard Model
The Standard Model is a theoretical
picture that describes
how the different elementary particles
are organized and
how they interact with each other along
with the different
forces. The elementary particles aresplit up into two families,
namely the quarks and the leptons.
Both of these families consist
of six particles, split into three
generations, with the first generation
being the lightest, and the third theheaviest. Furthermore, there are
four different force carrying particles
which lead to the interactions between
particles. The table below shows this all
a little bit more clearly.
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An interesting thing that has been discovered aboutmatter particles, is that each one has a corresponding
antiparticle. The term "anti" may be a bit deceiving, as
it is still real matter. The only difference between a
particle
and it's antiparticle is that an antiparticle has the oppositeelectrical charge.
Think of it as a mirror image. Here left and right are
the only
things to reverse when looking in the mirror.
Similarly, in the particle world,charge is what reverses when looking in the
"mirror". It's mass, spin and
most (quarks have somethingcalled color charge
which is also changed
in the "mirror") other properties are the same.
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In particle physics, Antimatter is the extension of the
concept of the antiparticle to matter, where antimatter is
composed of antiparticles in the same way that normal
matter is composed of particles. For example, an
antielectron (a positron, an electron with a positive charge)
and an antiproton (a proton with a negative charge) could
form an antihydrogen atom in the same way that an electronand a proton form a normal matter hydrogen atom.
Furthermore, mixing matter and antimatter would lead to the
annihilation of both in the same
way that mixing antiparticles and particles does, thus
giving rise to high-energy photons or other particleantiparticle pairs
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A positron is the antimatterequivalent of an electron. Like theelectron, the positron has a spin of ,and an extremely low mass (about1/1836 of a proton). The onlydifferences are its charge, which ispositive rather than negative
(hence the name), and its
prevalence in the universe, which ismuch lower than that of the electron.Being antimatter, if a positron comesin contact with conventional matter, it
explodes in a shower of pure energy,bombarding everything in the vicinity
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Antimatter
Almost every object observable fromthe Earth seems to be made of matterrather than antimatter. Many
scientists believe that thispreponderance of matter overantimatter (known asbaryon asymmetry) is the result of an
imbalance in the production of matterand antimatter particles in the earlyuniverse, in a process calledbaryogenesis
http://en.wikipedia.org/wiki/Baryon_asymmetryhttp://en.wikipedia.org/wiki/Baryogenesishttp://en.wikipedia.org/wiki/Baryogenesishttp://en.wikipedia.org/wiki/Baryon_asymmetry -
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When particles of matter and antimatter collide they annihilate each other,
creating conditions like those that might have existed in the first fractions of a
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This is where high energy accelerators come in. In head-oncollisions between high-energy particles and theirantiparticles, pure energy is created in "little bangs" whenthe particles and their antiparticles annihilate each other anddisappear. This energy is then free to reappear as pairs of
fundamental particles,e.g., a quark- antiquark pair, or an electron-positron pair, etc.Now electrons and their positron antiparticles can beobserved as two distinct particles. But quarks and antiquarksbehave somewhat like two ends of a string you can cut thestring and have two separate strings but you can never
separate a string into twodistinct "ends". Free quarks cannot be observed!
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Just as in the Big Bang, if we can
manage to make high enough
temperatures,
we can create some pairs of quarks &
anti-quarks, by the conversion of
energy
into matter. (Particles & anti-particles
have to be created in pairs to balance
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Quarks are a type of elementary particle and
are major constituents of matter. Quarks combine
to form composite particles called HADRONS, the
best-known of which are e.g. protons and neutrons
They are the only particles in the standard models
to experience the strong interactions addition to the
other three fundamental interactions fundamentalinteractions, also known as
fundamental forces.
http://en.wikipedia.org/wiki/Fundamental_interactionhttp://en.wikipedia.org/wiki/Fundamental_interactionhttp://en.wikipedia.org/wiki/Fundamental_interactionhttp://en.wikipedia.org/wiki/Fundamental_interaction -
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There are six types of quarks (plus their
six antiquarks),which are coupled into three pairs. They
are the up-down, the
charm-strange, and the top-bottom
(sometimes known as truth-beauty).
Another interesting fact about quarks
is that you can never find one by
itself, as they are always with other
quarks arranged to form a composite
particle. The name for these composite
particles is "hadrons". Quarks,
like protons and electrons, have
electric charge. However, their electric
charges are fractional charges, either
2/3 or -1/3
(-2/3 and 1/3 for antiquarks), and they
always arrange to form particles
with an integer charge (ie. -1, 0, 1, 2...).
Flavor
Mass
(GeV/c2
)
Electric
Char
ge
(e)
u up 0.004 +2/3
d down 0.08 -1/3
c charm 1.5 +2/3
s strange 0.15 -1/3
t top 176 +2/3
b bottom 4.7 -1/3
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Because quarks join with each other to form
particles with integer charge, not every kind ofcombination of quarks is possible. There are two
basic types of hadrons. 1) baryons, which are
composed of three quarks, and 2) mesons which
are made up of a quark and an antiquark.
Two examples of a baryon are the neutron and
the proton.And of mesons +kaon, -kaon, pion
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The proton is composed of two up quarks and one down
quark.
As you can see, when the charges from the individual
quarks are
added up, you arrive at the familiar charge of +1 for the
proton
1proton charge=2u+1d=2*2/3 +
1*(-1/3)=+1
Quarks Mass(GeV/c2)
Elect
ric
Charge
(e)
u up 0.004 +2/3
d down 0.08 -1/3
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The neutron is made up of two
down quarks and one up quark.
Again, adding the charges from
the quarks up, we arrive at zero.
An example of a meson is the pion.
It is composed of an up quark anda down antiquark. Because mesons
are a combination of particle and
antiparticle, they tend to be very
unstable and decay very quickly
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Like quarks, there are six types of leptons, and again, in three pairs.
Electron - neutrino, muon - neutrino, and tau - neutrino (these three
neutrino's are different from each other). The electron, muon, and tau
each carry a negative
charge, whereas the three neutrinos carry no charge. Leptons, unlike
quarks,exist by themselves, and, like all particles, have a corresponding
antiparticle.
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There are four fundamental forces in nature.
1. Electromagnetism
2. Strong
3. Weak
4. Gravity
These four forces all occur because
of the exchange of force carrier particles
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Well, pretend you want to knock a
bird out of a tree 100 yards away. You
must exert a force to do this, but the
darn bird is out of your reach. So, you
take out a pitching wedge and a golfball, take a swing. If you're good
enough, you will successfully exert a
force on the bird and knock it down
from its perch, with the golf ball being
the force carrier.
Not all types of matter though are affected
by all force carrying particles.
For example, the proton and electron are
affected by the force carrier particle
of the electromagnetic force, the photon.
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Electromagnetism is one of the two forces that dominateour everyday lives (the other one being gravity). The wordsyou are reading radiating from your monitor are a result ofelectromagnetism Theelectromagnetic force acts betweenall particles that have electricharge. It is attractive foroppositely charged particles, and repulsive for particles ofthe same charge
Interaction b/t electron and electron
Interaction b/t electron and proton
F =kQq/r^2
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The electromagnetic force gets weaker and weaker the further apart the particles are,
but it's range is infinite. The carrier of this force is the photon, most commonly observed
as light.
Another thing the electromagnetic force is responsible for is binding atoms together to
form molecules. Although most atoms have a net neutral charge, the positive charge from
within one atom can attract a negative charge within another atom, thus binding the two
atoms together. This is called the "residual electromagnetic force".
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This is the force between quarks particles which is verypowerful, thus it is called the "strong force".
The strong force is strictly an attractive force which acts between
nucleons (protons and neutrons). It attracts any combination of
protons and neutrons. i.e.. neutrons attract neutrons, protons attract
neutrons... This is the force that overcomes the repulsive force within
an atom due to the electromagnetic force and holds the nucleus together.
The strong force actually acts between quarks, and
it's the residual strong force (similar to the residual
electromagnetic force) that causes nucleons to
attract. The carrier of this force is the gluon ((
elementaryexpressions ofquarkinteraction, and
are indirectly involved with the binding ofprotons
andneutrons together in atomic nuclei.))
http://en.wikipedia.org/wiki/Elementary_particlehttp://en.wikipedia.org/wiki/Quarkhttp://en.wikipedia.org/wiki/Protonhttp://en.wikipedia.org/wiki/Neutronhttp://en.wikipedia.org/wiki/Atomic_nucleihttp://en.wikipedia.org/wiki/Atomic_nucleihttp://en.wikipedia.org/wiki/Neutronhttp://en.wikipedia.org/wiki/Protonhttp://en.wikipedia.org/wiki/Quarkhttp://en.wikipedia.org/wiki/Elementary_particle -
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All the stable matter in the universe appears to be made up
of one type of lepton (the electron) and two quarks (the up
and down), which compose the neutron and the proton.
However, there have been six types of each that have been
predicted and observed,The reason why we don't observe these more massive quarks and
leptons is due to the weak force. It is the weak force that causes massive
leptons and quarks to decay into lighter leptons and quarks.
The weak forces have weak strength as 10^9
times less than that of the strong nuclear force.
The term nuclear indicates that it is a
short-range force, limited to distances smaller
than an atomic nucleus
http://www.all-science-fair-projects.com/science_fair_projects_encyclopedia/Strong_nuclear_force -
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Gravity acts between all particles that have mass. Mass will attract
other mass with a force that gets weaker as the distance betweenthem gets larger. Gravity is responsible for the large scale structure
of the universe. Here's a pretty picture of a galaxy, which, of course,
is held together by gravity.
Although gravity appears to be a very powerful force, when it comes
to things on smaller scales, like tiny particles, can be ignored becauseof its weakness. The carrier of the gravitational force is the gravitron.
Although it has never been observed in experiment, it is strongly
believed to exist.
F =GMm/r^2
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Modern versions of Rutherford's
table-top experiment on the scattering of
alpha particlesoccupy many square
kilometers of land, with massive and costly
apparatus in underground tunnels
tens of kilometers long. These are the
particle accelerators that speed protons,
antiprotons, electrons, or positrons to near
the speed of light and then make
them collide head-on with each other or with
In an accelerator, focusing magnets and
bending magnets guide the beam of
particles around a ring. (Only a few of the
bending magnets are shown here). High
frequency microwave (RF) cavities
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Beyond this, the Universe holds at least two dark secrets:
Dark Matter and Dark Energy!
The total amount of luminous matter (e.g., stars, etc.) is
not enough to
explain the total observed gravitational behavior of
galaxies and clusters of
galaxies. Some form of mysterious Dark Matter has to be
found. Below we will
see how new kinds of particles may be discovered that fit
the description. Recent
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A Hubble Telescope photograph of galaxies deep in Universe
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We believe that the Universe
started off with a "Big Bang", with enormously high
energy and temperature
concentrated in an infinitesimally small volume. The
Universe immediately
started to expand at a furious rate and some of the
energy was converted into
pairs of particles and antiparticles with mass
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leaving just a tiny fraction of matter to carry
on in the Universe. As the Universe
expanded rapidly, in about a hundredth of a
second it cooled to a "temperature of about
100 billion degrees, and quarks began to
clump together into protons and neutrons
which swirled around with electrons,
neutrinos and photons in a
grand soup of particles. From this point on,
there were no free quarks to be found. In the
next three minutes or so, the Universe
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light nuclei such as deuterium, helium
and lithium. After about three hundred
thousand years, the Universe cooled
enough (to a few thousand degrees) to
allow the free electrons to become
bound to light nuclei and thus formed
the first atom. Free photons and
neutrinos continue to stream
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Presented by
Sanja K mar
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