Week 7 Compton Scattering & Threshold Energy

Question 1

what is the condition to have a massless particle and why

Answer 1

v = c

so that γ = infinity meaning that γm requires m to 0

Question 2

what is the energy equation for a massless particle

Answer 2

E = cp

Question 3

describe the Compton scattering experiment

Answer 3

fire a photon at a stationary particle

use a detector to measure the outgoing angle and energy of the resulting scattered particles

Question 4

what is the compton equation

Answer 4

1/E’ = 1/E + (1-cosθ) / mc^2

Question 5

what does the compton equation tell us

Answer 5

the relationship between the ingoing energy, outgoing energy and outgoing angle of the photon under the assumption it is massless

Question 6

what are the two ways to solve the compton equation

Answer 6

1 split the 4 vectors into their components straight away

2 stay in 4 vector for as long as possible

Question 7

what is it possible for a particle to do when colliding with another and what is the condition

Answer 7

to change into another particle if there is sufficient energy

Question 8

what is the name for the minimum sufficient energy required to allow a particle collision to take place

Answer 8

threshold energy

Question 9

what is the threshold energy equation if b is the new particle

Answer 9

E > Mbc^2

Question 10

if particles collide with threshold energy what happens afterwards

Answer 10

they are at rest since all energy was used to make the new particle so none is left over for kinetic energy

Question 11

if two particles are heading towards each other with equal but opposite momentum what is the procedure to solve the energy of the collision

Answer 11

1 we can view them as they are in the CoM frame at rest
2 calculate the invariant mass in the CoM frame
3 find E using the invariant mass