1.5- PARTICLE INTERACTIONS Flashcards
What can we use to measure forces?
newton meters and force sensors
What happens when a single force acts on an object?
it changes the momentum of the object
What is the momentum of an object?
its mass multiplied by its velocity
What happens when two objects interact?
exert equal and opposite forces on each other
What is transferred through these forces?
momentum
What is an example of this transfer of momentum?
two protons that approach each other. they repel each other and move away from each other
Which American Physicist worked out in detail about the transfer of momentum?
Richard Feynman
What did Richard Feynman say?
the electromagnetic force between two charged objects is due to the exchange of virtual photons
Why did Richard describe them as virtual photons?
we can’t detect them directly
Using what would be 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 skateboard
one of them throws ball at other
thrower recoils when the ball leaves their hand and other person recoils when they catch ball
What does the ball transfer in the analogy?
momentum from the thrower to the catcher so repel each other
What is the difference between the analogy and the exchange of a virtual photon between two like-charged particles?
we can’t detect the virtual photon
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?
a boomerang so the thrower and catcher attract each other
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 happens in both beta (+) and beta (-) decay?
a new particle and a new antiparticle are created
What is something 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
