1.5- PARTICLE INTERACTIONS Flashcards
What can we use to measure forces?
newton meters and force sensors
What is the momentum of an object?
its mass multiplied by its velocity
What is transferred through these forces?
momentum
What are exchange particles?
particle that causes the force between two particles in a particle interaction.
They are virtual particles
How long do exchange particles last?
Enough to transfer energy, momentum and other properties but overall a very short time
What did Richard Feynman say about the electromagnetic force between two charge particles?
the electromagnetic force between two charged objects is due to the exchange of virtual photons causing electrostatic repulsion.
Why did Richard describe them as virtual photons?
we can’t detect them directly
Using what would be used to intercept the virtual photons and what would happen?
using a detector
would stop the force acting
analogy for two like-charged particles
two people on ice skates:
What does the ball analogy not work for?
for two oppositely charged particles
What would the ball have to be changed to for two oppositely charged particles?
What are the exchange particles involved in the four fundamental forces called?
Gauge Bosons
What are the Gauge Bosons for strong nuclear force?
Pions (+,-,0)
What particles are effected by strong force?
Hadrons only
What is the Gauge Boson for electromagnetic force?
Virtual photon
What particles are effected by electromagnetic force?
charged particles only
What are the Gauge Bosons for weak force?
Bosons (W+, W-)
What particles are effected by weak force?
all types
What does the strong nuclear force do?
hold the neutrons and protons in the nucleus together
What does the weak nuclear force do?
cause a neutron to changed into a proton in beta (-) decay or proton to change into neutron in beta (+) decay
What determines the range of the force?
size of exchange particle
Heavier exchange particle =
smaller range = smaller range of force
How much more mass do W bosons have than protons
100 x more mass
Why can’t W bosons travel far?
High mass = creating it uses so much energy that it can only last for a short amount of time and it can’t travel far.
Why does electromagnetic force have infinite range?
It has no mass
What do each of the lines on a Feynman’s diagram represent?
What are the rules for drawing particle interaction diagrams?
What is something strange about the particle and antiparticle released in beta decay?
not a corresponding particle-antiparticle pair
one is an electron or positron
other is neutrino or antineutrino
How often do neutrinos and antineutrinos interact?
hardly interact with each other
Examples of neutrino and antineutrino interactions (2)
neutrino can interact with a neutron and make it change into a proton. beta(-) particle (electron) created and emitted as a result of change
antineutrino can interact with a proton and make it change into a neutron. beta (+) particle (positron) created and emitted as a result of change
What are the neutrino and antineutrino interactions due to?
the exchange of particles referred to as W bosons
3 things about W bosons
have a non-zero rest mass
have a very short range of no more than about 0.001fm
positively charged or negatively charged
How were W bosons first detected?
using the 2km diameter Super Proton Synchrotron at CERN in Geneva
What happened during the experiment at CERN?
protons and antiprotons at very high energies were made to collide and annihilate each other
at sufficiently high energies, annihilations produce W bosons as well as photons
What role does W bosons play in beta decay?
W boson meets neutrino and changes it to a beta(-) particle (electron)
W boson meets antineutrino and changes it to a beta(+) particle (positron)
What happens to the W boson if no neutrino or antineutrino is present?
W(-) boson decays into a beta(-) particle and antineutrino
W(+) boson decays into a beta (+) particle and neutrino
What does a beta minus decay look like in Feynman’s?
What does beta minus decay look like on Feynman’s?
What is electron capture?
sometimes a proton in a proton-rich nucleus turns into a neutron as a result of interacting through the weak interactions with an inner-shell electron from outside the nucleus.
In electron capture, what is the “acting particle”?
Therefore, what is the boson and what direction is it?
W+
What does electron capture look like on Feynman’s?
What does the W(+) boson change the electron to in electron capture?
a neutrino
When can a similar change to that of electron capture happen?
when a proton and electron collide at very high speed
For an electron with sufficient energy what can the overall change occur due to?
W(-) exchange from proton to proton
What is electron proton collisions?
What is the acting particle - which way is the boson?
What does it look like on feynman’s?
What are the photon and W boson known as?
force carriers as they are exchanged when the electromagnetic force and weak nuclear force act representatively
What is the exchange particle for EM repulsion?
Virtual photon
What does EM repulsion look like?
What is the pion known to be?
exchange particle of the strong nuclear force
What do scientists think the carrier of the force of gravity is?
graviton- bit it has yet to be observed
