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Particles

posted Feb 10, 2015, 3:42 AM by ranmini@charliesresearch.com   [ updated Aug 28, 2017, 9:44 PM by Upali Salpadoru ]
Sub atomic particles.

Atom was once considered to be indivisible. Then came the solar model of the atom with a positively charged nucleus with negatively charged electrons orbiting at a distance. The nucleus had protons and neutrons. Except the electron the other two have been smashed up into smaller units. The number of particles today exceed the number of elements.

 Table 1.  Fundamental particles according to Rutherford model of Atom and their present identity.

  Rutherford  view

                               Present view

Name of particle

           Remarks

Mass.

Charge

Particle type 

Anti particle

Electron

e-

Negatively charged particle that orbits the nucleus of atoms.

.

 

Mass= 1/1836 that of P+

-1

A Fermion.

 

Positron

Proton

P+

An indivisible particle in the atomic nucleus.

A composite particle.

Number of P+ in an atom is equal to its atomic number.

1amu.

+1

A Hadron.

Consists of 3 quarks.

Antiproton.

Neutron

An indivisible particle in the atomic nucleus.

A composite particle.

 

1amu.

0

P+ and e-

Anti neutron


Table 2. The elementary particles of the Standard Model include

El part..jpg

GROUP

PARTICLE

SYMBOL

MASS                      (Relative)

CHARGE

REMARKS /

DISCOVERY

Quarks

These can have fractional charges.


Up quark

 

u

_

+ (2/3)

“Well, in classical physics you could think of a quark as a point. In quantum mechanics a quark is not exactly a point; it’s quite a flexible object. Sometimes it behaves like a point, but it can be smeared out a little. Sometimes it behaves like a wave.”

 

Murray Gell-Mann,

Down quark

 

d

_

_ (1/3)

Beauty quark

 

b

____

_ (1/3)

Top quark

 

t

_____

+ (2/3)

Strange quark

 

s

___

_ (1/3)

Charm quark.

c

__

+ (2/3)

Leptons

electron

e-

0.51

- 1   

J J Thompson in 1897.

muon

µ

106

0

Predicted by Enrico Fermi in 1936.

Carl D. Anderson and Seth Neddermeyer at Caltech in 1936

tau

T-

1777

0

Carl Anderson in 1936

 

measurement do not succeed.

Muon neutrino

Vµ

1985 - A Russian team The mass is extremely small (10,000 times less than the mass of the electron.

0

 

Fred Reines and Clyde Cowan at the Control Center of the Hanford Experiment (1953)

Electron neutrino

Ve

0

 Clyde Cowan(1956)

Tau neutrino

Vt

0

Clyde Cowan, Frederick Reines

 

 

FORCE CARRYING PARTICLES

Gauge Bosons


Photon

Electro magnetic force.

Max Plank and Einstein.1905

W Bosons.

Weak nuclear force.

 

Z Bosons

 

Gluons

Strong force

 

Higgs Boson

 

LHC

Graviton ?

Exists according to some theories.

 

Composite Particles

Particles.jpg

Hadrons are not elementary particles but made of of quarks and anti quarks.

Barions are made up of 3 quarks.

Barion = u + U + d .

Mesons are made up of a quark and an anti-quark.

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