8.4 Creation and Annihilation of Matter Flashcards
When light acts as a particle, what are the particles called?
Photons
What are the characteristics of a photon?
No mass, charge or any number (baryon,lepton,strangeness)
Does have energy though
What is a photon denoted with in interactions?
γ (gamma)
What happens during pair production process? photon example
A photon with enough energy changes into matter and antimatter.
What is necessary to create e.g. tau and anti tau pair?
A photon with a great amount of energy
Why in the diagrams do the paths of the particle and antiparticle curve?
As there is usually a magnetic field present in the bubble chamber in those experiments, so that they curve in opposite directions due to opposite charges.
What is a photon?
A quantum of electromagnetic energy
What is conserved in both creation and annihilation of matter?
charge
momentum
mass-energy
How would we work out the minimum energy a photon must have to create an electron positron pair?
E = c^2 mx2
-As particles and antiparticles have the same mass
How would we work out the frequency or wavelength of a photon?
e = hc/(lambda) = hf
Can pair production only happen with photons?
No
What is the opposite of pair production?
Annihilation
How can we tell momentum is conserved from a diagram of bubble chamber experiment?
Equal but opposite curvature of particle and antiparticle
What happens when a particle meets its antiparticle?
They annihilate
What happens during annihilation? What EM is usually dissipated?
All the mass is converted into energy in the form of photons. Usually gamma rays
Where are antiparticles often used in real life situations?
In hospitals, they are used in PET scans
What are PET scans used for?
Monitoring activity in person’s brain. See which parts are active during activities.
Why during annihilation do the photons travel in opposite directions?
In order to conserve momentum
What are the characteristics of these photons?
They have the same energy.
Describe and explain the process of a PET scan.
A human receives an oxygen isotope (injection or normal intake). During the decay in the brain positrons are emitted, these almost immediately annihilate with electrons in the brain, producing 2 gamma rays. This EM radiation is detected by scintillator(placed from both sides) and the part of the brain that the photons comes from is deduced from the difference in time to reach scintillators. A computer produces the final image.
What would change if it was a antiproton and proton getting annihilated?
Due to greater mass loss, more energy would be released. Can be calculated using e = mc^2
