The neutron is classified as a hadron, because it is a composite particle made of quarks.

However, it has been decided not to put this data into the SysML model yet, because the Wikipedia page on Proton gives the mean charge radius, which can't be directly compared with the mean square radius. For now it suffices to introduce an indication isFiniteRadius for any Particle, which has been redefined in CompositeParticle to be 'true'.

We are told that:

Wikipedia: 'The neutron has no measurable electric charge. With its positive electric charge, the proton is directly influenced by electric fields, whereas the neutron is unaffected by electric fields.'

Wikipedia: 'The neutron has a magnetic moment, however, so the neutron is influenced by magnetic fields. The neutron's magnetic moment has a negative value, because its orientation is opposite to the neutron's spin.'

So the «undergoes» Dependency to Electromagnetism is qualified for now by naming it 'magnetism only'.

To match the Wikipedia units, a custom ValueType MagneticMoment has been created with custom Unit joule per tesla and symbol 'J/T'. (The tool's ISO-80000 has a ValueType magnetic area moment in equivalent ampere square metre units.)

Earlier in the trail a placeholder value property lifetime:ParticleLifetime was identified; this has now been renamed to meanFreeLifetime:ParticleLifetime to better correspond with:

Wikipedia: 'A free neutron is unstable, decaying to a proton, electron and antineutrino with a mean lifetime of just under 15 minutes (881.5±1.5 s).'

And it turns out after all that only free protons are definitely stable:

Wikipedia: 'Neutrons or protons bound in a nucleus can be stable or unstable, however, depending on the nuclide.'

Wikipedia: 'Beta decay, in which neutrons decay to protons, or vice versa, is governed by the weak force, and it requires the emission or absorption of electrons and neutrinos, or their antiparticles.'

Wikipedia: 'This radioactive decay, known as beta decay, is possible because the mass of the neutron is slightly greater than the proton.'

Some information about BetaDecay has been collected, but it's not the current focus.

Up next

A focus BDD for the AtomicNucleus block

Notes

[POLICY, STYLE]{STRICT} Webel Parsing Analysis «pa» diagrams are NOT intended as final presentation diagrams! They serve merely to traceably elicit model elements, which may then be shown in other (typically much tidier) presentation diagrams elsewhere.

[DISPLAY, STYLE, TIP]{SUGGESTED} Webel Parsing Analysis: If the dashed-line "anchors" from your «snippet» ElementGroup symbols to elicited elements make a «pa» Parsing Analysis Diagram (PAD) too hard to read, try making them light grey using symbol properties.

Snippets (quotes/extracts)