Unit 1 section 1 particle interactions


particle exchange

exchange particle: a virtual particle which allows forces to act in a particle interaction.


- skaters facing each other

- they throw a ball to each other

- each timer the ball is thrown and caught it transfers momentum, which is mass multiplied by velocity.


- skaters facing away from each other.

- each time a boomerang is thrown and caught it pushes the people together.

the people represent particles and the thrown object represents the exchange particle that causes the force.

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exchange particles

the strong interaction has the gluon, g as its exchange particle and the particles it affects are hadrons

the electromagnetic interaction has the virtual photon, y as its exchange particle and the particles it affects are only charged particles.

the weak interaction has the W+/W- boson as its exchange particle and it affects all types of particles

gravity possibly has the graviton as its exchange particle and it affect all types of particles.

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feynman diagrams

- exchange particles are represented by wiggly lines.

- other particles are represented by straight lines.

- incoming particles start at the bottom of the diagram and move upwards.

- baryons and leptons stay on seperate sides of the diagram.

- the W boson carries charge from one side of the diagram to the other - makes sure charges balance.

- a W- particle going left has the same affect as a W+ particle going to the right.

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particle interactions - B- decay


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particle interactions - B+ decay


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particle interactions - electron capture


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particle interactions - electron-proton collision


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particle interactions - electromagnetic repulsion


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