Particle Physics
Independent Study 2012
Victoria Jancowski
Units of Study
-Particles
-Quantum Physics
-The Grand Theory
-The Higgs Boson
-Relativity
-Scientists
Book Study: Understanding the Universe from Quarks to the Cosmos
Quarks à Atomic Nucleic Composants
Leptons à not inside atomic nuclei
Force à 4
-gravity: keeps all order on earth
-electromagnetic: governs behaviour of the electron around the nucleus
-weak: keep the sun burning. Partly responsible for volcanos and techtonic plates
-strong:keeps quarks inside mesons and baryons and holds them together. (void:strange)
Gauge Bosonsàforce carrying particles
-Gravity: Unproven (theorized gravitron)
-Electromagnetic: Photon (γ)
-Weak: W± and Z
-Strong: Gluon (g)
Fermionsàmatter carrying particles
-Quarks
-Leptons
* It is NOT understood why bosons carry force and fermions carry matter. To try and connect them physicist created a new theory.
**more on spin later
Supersymmetry(SUSY)
àthis theory attemps in explaining symetry between bosons and fermions and postulates additional fermions particles that are related to bosonic force carriers. and bosonic particles that are related to mass carrying fermions.
-Atoms are separated by an empty space called a void.
-like matter, energy can never be created nor destroyed. I goes through changes of state:
-Potential
-Kinetic
-Mass Energy (E=mc2)
Particle Decay
-Alpha decay: when a particle decays into another emiting an alpha particle (helium neucleus) and a new element with a mass 4 less and atomic number 2 less.
ex, 238 Urà 234 Th+ α
-Beta Decay: when an electron or positron is emmited from a particle. (not from the valence shell) There are 3 types of beta decay;
-β-
-β+
-ββ
Spin à Particles have spin. The spins that are allowed are:
-5/2, -2, -3/2, -1, -1/2, 0, ½, 1, 3/2, 2, 5/2
-Half integer spins are Fermions (mass carrying particles). Fermions are non social particles and it is impossible to have two of them in the same place at one time(exclusion principle).
-Integer spins are Bosons (force carrying partcles). They are considerd to be social and can be in the same place at one time.
The Anti-Matter Electron (Positron)
-physicists prposed that there was a possibility of an anti-electron. they came up with this equation.
X^2=1 à This equation is true for two values of X. +1 and –1
aniahlation
and emition of 2 photons
Strangenessà Some particles didn’t decay rapidly so physicists be came puzzled. Ordinairily if a force creates a particle it also decays it, and something was inhibiting the decay. This was strange and consequently these particles we said to have possed strangeness. It soon became apparent that the stangeness was something like an eleectric charge. Physicists soon discovered these particles were created in pairs. The reason why particles that possesed strangeness didn’t decay under the force they were created under (strong), was because the strangeness would react only under the weak force. Not via weak. The strong force can easilly create strange particle in pairs but only the weak force can destroy them.
Neutrinos
à neutrinos only interact with matter via the weak force, if even that. They are created in nuclear reactions.They can pass freely through material. Neutrinos rarely interact with matter but it does happen occationally. Physicists measured neutrinos and found two. (and for the longest time theorized a third) and at last they discovered a third:
- The Electron Neutrino (Ve)
- The Muon Neutrino (Vμ)
- The Tau Neutrino (VT)
Quarks: quarks make up many particles in forms of baryons and mesons and perhaps, soon, many more. All quarks have a spin of 1/2. and can have different color attributes. Quarks are situated in the nucleus of particles. The strong force binds quarks together.
Anti-Quarks:
-Anti-Quarks and quarks can be together as long as they are not the same flavour (red, green, blue.*** more on this later)
ex, π+
consists of an up quark and anti-down quark
bar over letters signifies anti.
_
u d
+2/3 +1/3 = 1 = charge
+1/2 -1/2 = 0 = spin
Leptons: leptons only interact with the weak, electromagnetic and gravitational forces. they have charges of 0 or 1. Leptons have a half-integer spin. falling under the category of fermions. There are 6 leptons:
-electron neutrino (Ve)
-muon neutrino (νμ)
-tau neutrino (VΤ)
-electron (e)
-muon (μ)
-tau (Τ)
Diagrams
A) Two particles carrying equal spin pointing in opposite directions have 0 net spin.
B) 2 particles carrying equal spin this time in the same direction have 1 as their net spin.
C) This is similar to but the particle orbit around eachother creating a net spin.
Mesons:
- mesons are made up of two quarks. One anti-quark and one normal quark. they are considered bosonic because they have an integer spin.
Quark Combination
|
Charge
|
Spin = 0
|
Spin = 1
|
Spin = 1
|
↑↓
|
↑↑
|
circular motion↑↓
| ||
dū
|
-1
|
∏-
|
p-
|
b-
|
sū
|
-1
|
K-
|
K*-
|
Ki*-
|
dѕ¯
|
0
|
K0
|
K*0
|
Ki*0
|
uѕ¯
|
1
|
K+
|
K*+
|
Ki*+
|
*These are only some of the many mesons.
Baryons: They have 3 quarks and none of which include anti-quarks.
- Quarks can explain 18 different baryons.
Commonly know baryons are protons and neutrons.
A special baryon the Δ++ (delta double plus) à spin of 3/2 (fermion)
- quark configuration of u↑u↑u↑
- this is a majour problem taking into consideration of the exclusion principle. ( no same fermion can be in the same place at the same time) And yet we have 3 up quarks…..same mass, charge and spin state.
As you can see in the diagram above, red, blue and green light make white. white is considered to be a neutral color and all baryons must neutral. so to solve this problem physicists added color u↑(red)u↑(blue)u↑(green).
-Quarks don’t actually carry visible color. Its just there to remind us that we need three to produce color objects.
-Quarks carry color therefor anti-quarks carry anti-color. (don’t think to hard about this one)
Now take messons there is a quark and anti quark. so to become white you have to put together the color and the anti color.
ex _
R + R = neutral. The same goes for blue and green.
The baryon situation is much more complicated.
R+GB= W
_ _
R+R = W …….Therefore R= GB
G+RB=W
_ _
G+G= W ……..Therefore G=RB
B+GR=W
_ _
B+B=W ……..Therefore B=GR
Baryons:
Particle Name
|
Symbol
|
Quark Content
|
Iso Spin
|
Elementary Charge
|
proton
|
p+
|
uud
|
1⁄2
|
1
|
neutron
|
n
|
udd
|
1⁄2
|
0
|
Lambada
|
λ0
|
uds
|
1⁄2
|
0
|
Sigma
|
∑+
|
uus
|
1
|
1
|
Sigma
|
∑0
|
uds
|
1
|
0
|
Sigma
|
∑-
|
dds
|
1
|
-1
|
Xi
|
Ξ0
|
uss
|
1⁄2
|
0
|
Xi
|
Ξ-
|
dss
|
1⁄2
|
-1
|
Double Charmed Xi
|
Ξ++
|
ucc
|
1⁄2
|
2
|
Double Charmed Xi
|
Ξ++
|
dcc
|
1⁄2
|
1
|
Charmed Omega
|
Ω0
|
ssc
|
0
|
0
|
Bottom Omega
|
Ω-
|
ssb
|
0
|
-1
|
Delta Double plus
|
Δ++
|
uuu
|
3⁄2
|
2
|
Delta Plus
|
Δ+
|
uud
|
3⁄2
|
1
|
Delta Zero
|
Δ0
|
udd
|
3⁄2
|
0
|
Delta Minus
|
Δ-
|
ddd
|
3⁄2
|
-1
|
*these include only some of the many baryons that are formed.
The Standard Model
The stamdard model is a theorized model of elementary particles that are the basis of matter. As you can see it containes quarks and leptons and the forces (some of which contain colors). This model is able to explain everything we know about physics, but it falls short in the way that it does not incorperate the physics of dark energy nor, the full theory of gravitation as described by the theory of general relativity. The model also does not contain any viable dark matter particle that posesses required properties deduced from observational cosmology. Nor does it account for neutrino oscillations. There is three generations in the vertical colomns. Generation I is the most stable and Generation III is the least stable. The Standard model is not a completed theory but it a simple yet elegant theory.
