Date | May 2019 | Marks available | 3 | Reference code | 19M.3.HL.TZ1.6 |
Level | Higher level | Paper | Paper 3 | Time zone | 1 |
Command term | Show that | Question number | 6 | Adapted from | N/A |
Question
The particle omega minus () decays at rest into a neutral pion () and the xi baryon () according to
The pion momentum is 289.7 MeV c–1.
The rest masses of the particles are:
: 1672 MeV c–2
: 135.0 MeV c–2
: 1321 MeV c–2
Show that energy is conserved in this decay.
Calculate the speed of the pion.
Markscheme
momentum of xi baryon is also 289.7«MeVc−1» ✔
total energy of xi baryon and pion is «MeV» ✔
which equals the rest energy of the omega ✔
Allow a backwards argument, assuming the energy is equal.
✔
✔
Award [2] for bald correct answer.
Examiners report
Energy conservation in a decay. This relativistic mechanics question was very challenging. Only a few candidates were able to calculate the total energy of the baryon and pion, despite being able to recognize the correct momentum of the baryon.
Energy conservation in a decay. This relativistic mechanics question was very challenging. Only a few candidates were able to calculate the total energy of the baryon and pion, despite being able to recognize the correct momentum of the baryon. The same for the speed of the pion in b), most of the attempts demonstrated by candidates were not relevant.