| Date | May 2017 | Marks available | 2 | Reference code | 17M.2.SL.TZ1.5 |
| Level | Standard level | Paper | Paper 2 | Time zone | Time zone 1 |
| Command term | State | Question number | 5 | Adapted from | N/A |
Question
A possible decay of a lambda particle (\({\Lambda ^0}\)) is shown by the Feynman diagram.
State the quark structures of a meson and a baryon.
Explain which interaction is responsible for this decay.
Draw arrow heads on the lines representing \({\bar u}\) and d in the \({\pi ^ - }\).
Identify the exchange particle in this decay.
Outline one benefit of international cooperation in the construction or use of high-energy particle accelerators.
Markscheme
Meson: quark-antiquark pair
Baryon: 3 quarks
Alternative 1
strange quark changes «flavour» to an up quark
changes in quarks/strangeness happen only by the weak interaction
Alternative 2
Strangeness is not conserved in this decay «because the strange quark changes to an up quark»
Strangeness is not conserved during the weak interaction
Do not allow a bald answer of weak interaction.
arrows drawn in the direction shown
Both needed for [1] mark.
W −
Do not allow W or W+.
it lowers the cost to individual nations, as the costs are shared
international co-operation leads to international understanding OR historical example of co-operation OR co-operation always allows science to proceed
large quantities of data are produced that are more than one institution/research group can handle co-operation allows effective analysis
Any one.
