nucleon
Enable an AI agent to identify a proton or neutron as a nucleon, record its physical context, and judge which descriptions, measurements, and transformations apply.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
recalled by Codex without web access - no source was read
Researched by: Codex
Purpose and description
Enable an AI agent to identify a proton or neutron as a nucleon, record its physical context, and judge which descriptions, measurements, and transformations apply.
A nucleon is a proton or neutron, a composite spin-1/2 baryon that participates in the strong interaction and constitutes ordinary atomic nuclei.
It can be Classify a candidate as a proton or neutron using charge, baryon identity, and experimental evidence.; Select a free-particle or nuclear many-body description appropriate to the physical context and probe scale.; Construct and check a proposed reaction channel using charge, baryon-number, energy, momentum, and angular-momentum accounting.; Relate measured scattering or magnetic observables to nucleon structure under an explicit interpretation model.; Assess whether a species-changing process is energetically available in the recorded free or bound state.; Record preparation, polarization, scattering, or detection procedures through their associated experimental systems..
Distinguishing features
A nucleon is a proton or neutron; membership in the broader baryon category alone is insufficient.
A proton has electric charge +1 e and a neutron has charge 0 e; electrical neutrality does not make a neutron an elementary neutral particle.
A nucleon is a composite spin-1/2 baryon with baryon number +1, distinguishing it from leptons, mesons, and antinucleons.
Proton and neutron valence-quark content is uud and udd respectively; these labels specify net flavour content without exhausting the quark and gluon structure.
A nucleon can exist outside a nucleus, while a nucleus is a nuclear system; an ordinary hydrogen nucleus is the special case consisting of one proton.
Scope
+ Proton or neutron identity and the properties shared by nucleons
+ Quark and gluon structure and the limits of constituent descriptions
+ Free, nuclear-bound, and scattering states
+ Nucleon interactions, transformations, and conservation constraints
+ Measurement context and uncertainty for nucleon properties
- Whole-nucleus composition, collective structure, and isotope classification
- Atomic electron configurations and chemical bonding
- Quarks and gluons treated as independently modelled particle categories
- Antinucleons as physical instances, except as comparison or reaction partners
- Other baryons and excited baryon resonances as independent particle categories
- Accelerators, detectors, and experimental facilities as equipment
Characteristics
- Nucleon species
- proton | neutron Determines charge, species-specific reference properties, and allowed reaction assignments.
- Electric charge
- e; proton +1, neutron 0 Constrains electromagnetic interactions and charge conservation.
- Intrinsic spin
- spin quantum number s = 1/2 Establishes fermionic behaviour and the allowed spin projections.
- Polarization
- spin density matrix or polarization vector relative to a specified basis Separates a prepared or inferred spin state from intrinsic spin.
- Baryon number
- +1 Distinguishes a nucleon from its antiparticle and supports reaction bookkeeping.
- Rest mass
- MeV/c²; species-specific reference value with source and uncertainty Supports free-particle kinematics without conflating rest mass with nuclear effective mass.
- Physical context
- free | nuclear-bound | scattering | other explicitly specified many-body context Determines which kinematic, stability, and interaction descriptions apply.
- Nuclear host
- reference to a nucleus and its state, when applicable Connects a bound nucleon to the system governing its binding and available transitions.
- Four-momentum
- energy in MeV and momentum in MeV/c, with reference frame and inference method Enables reaction analysis while exposing assumptions in assigning bound-nucleon kinematics.
- Magnetic moment
- nuclear magnetons, with sign and species Captures magnetic coupling, including the neutron's nonzero magnetic moment despite zero net charge.
- Spatial-structure observable
- specified form factor or radius convention; fm or fm² where appropriate Prevents charge, magnetic, and matter distributions from being collapsed into a single hard-sphere size.
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 5 bundles · 9 layers · 15 findings · 28 questions.
Species and quantum identity Establishes which nucleon is represented and the quantum labels that identify it.
Nucleon properties combine shared baryon characteristics with proton-neutron differences that change physical predictions.
Proton-neutron membership
Defines category membership and its boundaries against neighbouring particle and nuclear categories.
Species assignment
A nucleon assignment resolves to proton or neutron and distinguishes category membership from membership in a nucleus.
- What evidence identifies this nucleon as a proton or neutron? definition
- Does the record describe an individual nucleon, a one-proton nucleus, or a larger nuclear system? boundary
Quantum labels and spin state
Separates intrinsic particle properties from prepared states and approximate symmetry labels.
Intrinsic versus prepared properties
Charge, baryon number, and intrinsic spin identify the particle, while polarization specifies its state; isospin assignments require an explicit convention.
- Which intrinsic quantum labels are assigned, and do they agree with the selected nucleon species? definition
- How was polarization determined, and relative to which axis or basis? measurement
- If isospin is used, which projection convention and symmetry-breaking limitations apply? boundary
Composite structure and probes Connects quark and gluon descriptions to the observables that resolve nucleon structure.
Treating a nucleon as either elementary or merely three static quarks loses essential distinctions between useful physical descriptions.
Quark and gluon description
Records net flavour content while retaining the scale dependence of more detailed constituent descriptions.
Valence content and description scale
The uud and udd assignments encode valence content; descriptions of sea quarks, gluons, and momentum distributions require additional theoretical and scale information.
- Is the description limited to net valence flavour, or does it include resolved quark and gluon distributions? definition
- Which resolution scale, theoretical framework, and source support the stated internal structure? provenance
Electromagnetic structure
Distinguishes magnetic moments, form factors, and radius definitions.
Observable-specific size and coupling
Nucleon size is inferred through specified observables, and zero net neutron charge does not imply absent electromagnetic structure.
- Which form factor, magnetic moment, or radius definition is being reported? measurement
- What experiment, extraction method, uncertainty, and momentum-transfer range support the value? provenance
- Would interpreting this value as a positive geometric radius misrepresent the observable, particularly for neutron mean-square charge radius? boundary
Free and bound description Records the environment and kinematic assumptions needed to describe the nucleon.
Free-particle properties cannot be transferred unchanged into every nuclear calculation or interpreted as independently measurable bound-particle attributes.
Nuclear embedding
Connects a bound nucleon to its host nucleus and the many-body description being used.
Host and state assignment
Nuclear membership and orbital or configuration assignments depend on the host state and nuclear model; identical nucleons need not have individually trackable identities.
- Is the nucleon free or bound, and which nucleus and nuclear state provide its context? definition
- What nuclear model supports any orbital, occupancy, or individual-nucleon assignment? provenance
- Does the proposed record incorrectly treat indistinguishable nucleons as persistently labelled classical particles? boundary
Kinematics and binding
Separates reference rest mass from context-dependent energy and momentum assignments.
Energy-momentum interpretation
Kinematic records identify the frame and distinguish free rest mass, inferred bound-nucleon quantities, effective mass, and nuclear separation energy.
- In which frame and by which measurement or calculation were energy and momentum assigned? measurement
- Is the quoted mass or energy a free rest mass, model-dependent effective quantity, or property of a nuclear removal process? boundary
Interactions and transformations Describes how a nucleon scatters, participates in nuclear reactions, and changes species through weak processes.
An agent needs process-specific constraints to distinguish allowed transformations from unsupported inferences based only on particle identity.
Scattering and nuclear reactions
Records reaction partners, energy regimes, channels, and the evidence supporting predicted outcomes.
Channel and interaction regime
Elastic scattering, inelastic excitation, capture, and particle production require different kinematic and interaction descriptions.
- Which initial particles or nuclear systems, collision energy, and final channel define the process? definition
- Which measured cross section or validated calculation supports the predicted outcome in this energy range? provenance
- Does the proposed channel satisfy the applicable conservation laws and energy threshold? action
Weak conversion and stability
Distinguishes free-neutron decay from environment-dependent proton-neutron conversion.
Context-dependent conversion
Free neutrons undergo beta decay; nuclear binding and total-system energetics determine whether corresponding conversions are available in a nucleus.
- Is the proposed process free-neutron beta decay, nuclear beta decay, electron capture, or another specified weak reaction? definition
- Do the complete initial and final systems make the conversion energetically possible, including required leptons? action
- Which measurement and physical context support any lifetime, branching fraction, or stability claim? provenance
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Check these first
Recalled without web access and unsourced; every item is a lead to verify.
- This entry covers the particle-physics sense, including free nucleons and nucleons bound in nuclei.
- Numerical values are recalled approximations; precision work should verify evaluated particle data, especially the free neutron lifetime, for which measurement methods have yielded discrepant results.
- No nucleon-specific regulatory standard is asserted; radiation protection requirements apply to particular sources, facilities and uses.
- Which of these check these first hold for the sense of nucleon this model covers, and on what evidence? provenance
Kinds and varieties
Recalled without web access and unsourced; every item is a lead to verify.
- Proton
- Neutron
- Which of these kinds and varieties hold for the sense of nucleon this model covers, and on what evidence? provenance
Identifiers and schemes
Recalled without web access and unsourced; every item is a lead to verify.
- Particle Data Group Monte Carlo particle numbering scheme - 2212 (proton); 2112 (neutron) - These codes distinguish the two nucleon species.
- Which of these identifiers and schemes hold for the sense of nucleon this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Nucleon counts specify nuclear composition: proton number identifies the element, and neutron number distinguishes its isotopes.
- Nuclear structure and reaction calculations describe interactions among nucleons.
- Proton beams are used in particle research and radiotherapy.
- Neutrons are used in scattering experiments, material analysis and nuclear chain reactions.
- Which of these real-world use hold for the sense of nucleon this model covers, and on what evidence? provenance
Typical measurements
Recalled without web access and unsourced; every item is a lead to verify.
- Free-particle rest mass - Approximately 938.272 for a proton; 939.565 for a neutron - MeV/c²
- Electric charge - +1 for a proton; 0 for a neutron - elementary charge
- Spin quantum number - 1/2 for both species - dimensionless
- Free neutron mean lifetime - Approximately 880 - s
- Which of these typical measurements hold for the sense of nucleon this model covers, and on what evidence? provenance
Failure modes and hazards
Recalled without web access and unsourced; every item is a lead to verify.
- Energetic proton radiation can damage biological tissue and electronic components.
- Neutron radiation can cause biological damage and activate materials through nuclear reactions.
- A free neutron undergoes beta decay; this instability does not imply that neutrons bound in stable nuclei decay.
- Which of these failure modes and hazards hold for the sense of nucleon this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Recalled without web access and unsourced; every item is a lead to verify.
- Baryon - Baryon is the broader particle class; nucleon specifically denotes a proton or neutron.
- Quark - Quarks are elementary constituents; nucleons are composite systems containing quarks, antiquarks and gluons.
- Atomic nucleus - A nucleus is the central nuclear system of an atom, ordinarily containing one or more nucleons; a nucleon is an individual proton or neutron.
- Electron - An electron is an elementary lepton, whereas a nucleon is a composite baryon.
- Antinucleon - An antinucleon is an antiproton or antineutron, with baryon number opposite to that of a nucleon.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of nucleon this model covers, and on what evidence? provenance
What the second pass must settle
- Does the existing Vercy catalogue already contain a nucleon model or proton and neutron models to which this entry should link?
- Which authoritative reference values, uncertainty conventions, and experimental determinations should supply masses, magnetic moments, radii, and the free-neutron lifetime?
- Which nuclear frameworks should be supported for bound-state assignments, effective masses, and removal energies, and how should their incompatible conventions be exposed?
- Where should the catalogue place the boundary between a nucleon undergoing excitation and an independently represented baryon resonance?
- Which probe-energy ranges and applications must the first researched model support, determining how much form-factor, parton, and reaction-channel detail is necessary?