Exchange Particles And Feynman Diagrams Flashcards
Particle exchange explain repulsion and ……
Attraction
What are forces caused by
Particle exchange
What are the exchange particles called
GAUGE BOSONS
Virtual particles- only exist very short time
What is the repulsion between two protons caused by
Exchange of VIRTUAL PHOTONS- the gauge bosons of the electromagnetic force
Name the 4 fundamental forces, each gauge boson and the particles affected
Type of interaction/Gauge boson/Particles affected
Strong/gluon/hadrons only
Electromagnetic/photon(y)/charge particles only
Weak/W+W-Z0/all types
Gravity/graviton?/all types
Why do particle physicist never bother about gravity
Incredibly FEEBLY comPared to other types of interaction
Only really matters BIG MASSES- stars planets
Graviton may exist- no evidence
The larger the mass of a gauge boson the …. The range of force
Shorter
Why does the W boson have a very SHORT RANGE
Mass of 100 times that of a proton
Creating a virtual W particle used so much ENERGY
that it can only EXIST short time
And can’t TRAVEL far
Name which gauge boson has an infinite range and why
PHOTON as it has ZERO MASS
How are GAUGE BOSONS represented in Feynman diagrams
Wiggly lines
How are other particles represented in Feynman diagrams
Straight lines
What are the three rules for drawing Feynman diagrams
1) INCOMING particles start at the BOTTOM of the diagram and move upwards
2) The BARYONS stay on one side and the LEPTONS stay on the other
3) CHARGES on both sides must be balanced
What happens in electromagnetic repulsion
When 2 particles with EQUAL CHARGES get close to each other, they REPEL
(Exchange of a virtual photon) going to the LEFT
Explain electron capture
Of course E & P attracted by ELECTROMAGNETIC INTERACTION between them
But if P CAPTURED an E
The WEAK INTERACTION can make this happen
Explain the Feynman diagram for electron capture
Bottom left PROTON
Bottom right ELECTRON
Gauge boson of W+ going RIGHT
Top left NEUTRON
Top right ELECTRON-NEUTRINO
What is a electron-proton collision
Electron COLLIDES with a proton
Equation same as electron capture but (W-) boson (left)
A W- particle going to the left has the same effect as a W+ particle going to the ….
Right
What does the W bosons carry from one side of a Feynman diagram to the other
Charge
In order to make each side balanced
Describe the Feynman diagram for a beta-plus(minus) decay
Bottom NEUTRON (proton)
W- gauge boson traveling right
Top left PROTON (neutron)
Top right ELECTRON (positron)
Top right second ANTINEUTRINO (neutrino)
Talk about electron capture in more detail
Orbiting electron
Interacts with proton from nucleus
U quark changes to a D quark
(Neutron gives off from proton)
State one difference between a W exchange particle and a photon
Photon has 0 mass
Similarities between Hadrons and leptons
Both have rest mass
Both affected by weak interaction
Both experience electromagnetic interaction
