More on the Elementary Particles and Forces in the Universe. Dr. Mike Strauss The University of Oklahoma. Two Questions Asked for Centuries. 1) What are the fundamental objects from which everything else in the universe is made?
Dr. Mike Strauss
The University of Oklahoma
1) What are the fundamental objects from which everything else in the universe is made?
2) What are the forces or interactions that hold these objects together and how do these forces work?
Ancient Greece (followers of Thales)What are the fundamental objects in the universe from which everything else is made?
At the turn of the century, (that is in 1900) two fundamental forces were known:
ElectromagnetismHow are the fundamental objects held together?or in more precise scientific languageWhat are the fundamental forces of nature?
Particles fundamental forces were known:
Latin for “Light”
Usually found alone
A nonsense word in Finnegan’s Wake by James Joyce
Always found in groupsThe Fundamental Particles in the Universe(Current Model)
The Atom fundamental forces were known:
are buried deep
inside the nucleus.
Forces fundamental forces were known:
Weak Nuclear Force
Strong Nuclear Force
Only quarks and particles made from quarks (hadrons) interact via this force
ElectroweakThe Fundamental Forces in the Universe(Current Model)
Charge = +2/3e fundamental forces were known:
Charge = -1/3e
Not yet discoveredThe Standard Model:A Theory of Everything (except gravity)
The Fundamental Particles: (Fermions)
u c t
d s b
The Fundamental Forces: (Bosons)
Strong force: 8 gluons
Weak force: W+, W-, Z0
And: Higgs Boson: H
(plus a lot of Nobel Prize winning math)
Antiparticle:Every particle, including quarks, has an antiparticle. The charge and “quantum numbers” of the antiparticle are opposite that of the particle, and the mass is the same.
Hadron:Any particle made of quarks and/or antiquarks.
Baryon:Any particle made of three quarks. (Antibaryons are made up of three antiquarks.)
Meson:Any particle made of a quark and an antiquark.
Baryons fundamental forces were known:Mesons
p: uud : ud
n: udd : uu
uds : ud
: sss K: us
c:udc D: cu
p: uudSelected Hadrons (Hundreds of hadrons have been discovered)
(electric charge)(electric charge)
*A theory combining these two into an “electroweak” force was developed in the 1960’s and verified in 1983.
Gravity Graviton* All 10-38
EM Photon Charged 10-2
Weak W+, W-, Z0 All 10-1 <10-18 m
Strong Gluons (8) Quarks/Gluons 1 10-15 m
*Not yet discovered. Not part of the “Standard Model”
Looking Inside Very Small Objects fundamental forces were known:
“The Results”Earnest Rutherford’s 1911 Experiment
Rutherford proposed the “Nucleus” to explain the results.
Deep Inelastic Scattering
The Wave Nature of Matter fundamental forces were known:
The de Broglie Wavelength
h = 6.63 10-34 Js
p = mv (momentum)
In order to “see” an object, the wavelength of the probe must be smaller than the object being observed.
E = m0c2
E2 = m02c4
E2 = m02c4 + c2p2
Answer: Mass is a form of energy. If I can concentrate enough energy at any point (even energy of motion—kinetic energy), I can create any particle(s) with mass.
Step 1: Accelerate two particles towards each other. They have a lot of energy from their motion, kinetic energy.
Step 2: Let them collide and annihilate each other to create energy or other particles.
Step 3: That energy can create any particle and its antiparticle with mass less than or equal to the total energy (E=mc2).Particle accelerators can create matter (from other forms of energy)
“Feynman” Diagram of e have a lot of energy from their motion, kinetic energy.+e-Annihilation
Photon or Z0
1. Quarks created from initial annihilation have a lot of energy from their motion, kinetic energy.
2. Strong nuclear force acts like a rubber band
3. Eventually the “rubber band” breaks creating new quarksCreating Hadrons
Photon or Z0
What about the forces? have a lot of energy from their motion, kinetic energy.Why are they described by particles?
The interaction between two particles can be thought of as the two particles exchanging another particle. In this case, the two people throw a basketball back and forth to change their momentum. The basketball is the “carrier” of the force or interaction.
e have a lot of energy from their motion, kinetic energy.+
Now consider an electron (with a negative charge)
and a positron (with a positive charge) approaching each other at a rapid rate.
This can be thought of as the two particles exchanging a “photon” which, in turn, changes their direction as indicted in this Feynman Diagram
(The following masses are in GeV/c “photon” which, in turn, changes their direction as indicted in this Feynman Diagram2)
Up quark (u): 0.0004 Down quark (d): 0.0007
Charm quark (c): 1.5 Strange quark (s): 0.15
Top quark (t): 175 Bottom quark (b): 4.7Different quarks have different masses
The equation E=mc2 is used to define the mass of an object. In these units, a proton has a mass of about 1 billion electron volts (1 GeV/c2).
The mass of just one top quark is more than the entire mass of a gold nucleus which has 79 protons and 118 neutrons, or more than 591 up and down quarks!
Quarks have fractional charge “photon” which, in turn, changes their direction as indicted in this Feynman Diagram
In a very basic model:
A neutron is made of 3 quarks: up, down, down (udd)
Charge: +(2/3) - (1/3) - (1/3) = 0
A proton is also made of 3 quarks: up, up, down (uud)
Charge: +(2/3) + (2/3) - (1/3) = 1
All the properties of the neutron and proton can be derived from the properties of its constituent particles.
The force that holds quarks together is called the strong nuclear force.
There are 3 types of strong nuclear charge which can attract quarks to each other and cause them to bind together.Why are quarks always bound together?
Larry, Curly, Moe nuclear force.
knife, fork, spoonStrong charge
anti-larry, anti-curly, anti-moe
Every color is attracted to its anticolor nuclear force.
colorThree strong charges
Quantum Chromodynamics (QCD)
Baryons: nuclear force.
1 green, one red, one blue
Constantly changing color
Antibaryons have 3 anti-quarks
With 3 different anti-colors constantly changing
1 quark and 1 anti-quark
Color and anticolor constantly changing
EtaHadrons in nature are colorless
Quark and Gluon Color nuclear force.
E nuclear force.1
E2Virtual Particles Exist!
It’s as if a tennis ball changed into a bowling ball and an “anti”-bowling ball for a brief moment, before turning back into a tennis ball.
DE = E2 E1
Question: nuclear force.The neutron has a mass of about 1 GeV/c2 and the W has a mass of about 84 GeV/c2. How is energy conserved in neutron decay?
Answer: During the very brief period of time that the W exists, energy is not conserved? ...How can this be?
Heisenberg’s Uncertainty Principle:
So if d <h/2mc a “virtual” particle can be produced.
(h = 6.63 10-34 Js)
Benefits of High Energy Physics nuclear force.