particle physics with sanjay 630mod2

8/14/2019 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

particle physics with sanjay 630mod2

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