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Quark:, exchange particle and forces:, Lepton, strangeness:, Boson: -…
Quark:
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Quark confinement: quark can't exist individually.
As strong nulear force appear, two particles are so close so that it needs high energy to separate them. This high energy will transfer to mass. Therefore, if we separate two particles, new pairs will be generated.
The proton is a baryon made out of two u quarks and one d quark, uud. The neutron is another baryon made out of two d quarks and one u quark, ddu.
The electric charge of the proton is thus predicted to be:
Qp = + 2/3 e + 2/3 e − 1/3 e = e
and that of the neutron is predicted to be:
Qn=−1/3e −1/3e+2/3e=0
Pions are examples of mesons.The positively charged pion (π+ meson) is made up as follows:
π+ = (ud–)
explanation: The bar over the ‘d’ shows this is an anti-particle.Thus, the positive pion is made out of a u quark and the anti-particle of the d quark (the d anti- quark).
Apart from electric charge, quarks have another property called baryon number, B.
Each quark is assigned a baryon number of +1/3 and each anti-quark a baryon number of −1/3.
To find the baryon number of the hadron
that is formed by quarks, just add the baryon numbers of the quarks in the hadron.
For example:
uct baryon number = +1/3 +1/3 +1/3 = +1 (a baryon)
ud– baryon number = +1/3 −1/3 = 0 (a meson)
In all reactions electric charge and baryon number are conserved, i.e. they have the same value before and after the reaction.
For example: In alpha minus decay, d becomes u+(e^-)+(antiVe).
In this case, for conservation of charge, the charge of d is -1/3e, the charge on the right is 2/3e-1e+0. Therefore, both sides are equal to -1/3e. So charge number is conserved.
In the same reaction, the baryon number at the left and right are both 1/3, so the baryon number is also conserved.
Quark was first proposed by two physicists independently: Murray Gell-Mann and Georg Zweig.
Top and bottom quarks are alternatively called truth and beauty.
There is six different flavors of quarks and there are anti-particles of each of these.
These have the same mass but all other properties are opposite, for example electric charge.
Quarks combine in just two ways to form other particles called hadrons.
A hadron is a particle made out of quarks.
When three quarks combine they form a baryon. (When three anti- quarks combine they form an anti-baryon.)
When a quark combines with an anti-quark they form a meson.
exchange particle and forces:
There are four types of forces: gravitational, weak nuclear force, strong nuclear force and electromagnetic force.
For gravitational force, it acts on particles with mass; for weak nuclear force, it acts on quarks and leptons only responsible for beta decay; for strong nuclear force, it acts on quarks by extension particles made out of quarks, i.e. hadrons; for electromagnetic force, it acts on particles with electric charge.
Particles involve during exchange: electromagnetic: photon.
weak: W plus , W minus and Z^0.
strong: gluons/mesons.
gravitational: gravitation.
Relative strength: electromagnetic (1/137); weak (10^-6); strong(1); gravitational (10^-41)
Force= action+reaction=interaction=charge=events.
Range: electromagnetic(infinity); weak( 10^-18m); strong (10^-15m); gravitational (infinity)
Lepton
There are six types of lepton.These are the electron and its neutrino, the muon and its neutrino, and the tau and its neutrino.They are denoted by e−, ν , μ−, ν , and τ−, ν .
All leptons interact with the weak nuclear interaction. Those that have electric charge (e−, μ− and τ−) also interact with the electromagnetic interaction.
Leptons are elementary particles. Different than quarks, they can appear individually.
Lepton numbers are conserved. For example,
μ+ → (e^+)+νe+anti-νμ
In this case, lepton number at the left is -1; lepton number at the right is -1+1-1. Left lepton number=right lepton number, so it is conserved.
strangeness:
The reason of calling it strangeness is because it is abnormal regarding to the high decay time.
All quarks have strangeness number of zero.
strange quark have strangeness number of negative one.
anti-strange quarks have a strangeness of one.
Strangeness is conserved except weak nucleus force acts on it.
Boson:
Boson includes W^+, W^- and Z^0.