hadron
Enable an AI agent to recognise a hadron, assess evidence for its identity and physical state, and determine which descriptions, measurements and interaction processes 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 recognise a hadron, assess evidence for its identity and physical state, and determine which descriptions, measurements and interaction processes apply.
A hadron is a composite, colour-neutral particle whose quark, antiquark and gluon degrees of freedom are bound by the strong interaction described by quantum chromodynamics.
It can be Match a reported particle or resonance to a hadron identity using compatible quantum numbers, mass and observed channels.; Check proposed production and decay channels against kinematics and conservation rules appropriate to the interaction.; Select reconstruction signatures using decay products, lifetime and detector sensitivity.; Compare property measurements while preserving uncertainty, conventions and analysis dependence.; Record competing internal-structure interpretations without converting them into established constituent facts..
Distinguishing features
A hadron is a colour-neutral composite system governed by the strong interaction; participation in the strong interaction alone does not distinguish it from a quark or gluon.
Being composite is insufficient: atoms and ordinary atomic nuclei belong to neighbouring models rather than becoming single hadrons.
Baryon number distinguishes baryonic from mesonic assignments; electric charge alone cannot make this distinction.
Boson and fermion describe spin statistics, whereas hadron describes a different classification axis: mesons and baryons must not be collapsed into a single spin-statistics category.
A peak in a reconstructed mass distribution is evidence to assess, not by itself sufficient identification of a new hadron.
Scope
+ Hadron identity, nomenclature and classification into baryonic or mesonic families
+ Quark-flavour content, colour neutrality and the limits of constituent descriptions
+ Quantum numbers, mass, size and electromagnetic properties
+ Production, strong-interaction behaviour, decay and stability
+ Experimental identification and the status of candidate or established hadronic states
- Quarks and gluons as separately modelled elementary particle kinds
- Leptons, photons and other elementary particles that are not hadrons
- Atomic nuclei as bound systems of nucleons and possible additional constituents
- Atoms, molecules and bulk hadronic matter
- Detector apparatus, accelerator facilities and complete experimental events
- Quantum chromodynamics as a theory independent of a particular hadronic system
Characteristics
- Referent level
- species | individual occurrence | candidate state Prevents species properties from being confused with an individual particle's measured trajectory or an unconfirmed signal.
- Hadron family
- baryon | antibaryon | meson | unresolved Organises identity and applicable quantum-number assignments without assuming a particular internal arrangement.
- Quark-flavour content
- specified flavour content or superposition; proposed assignments labelled explicitly Supports family assignment and reaction accounting while separating flavour labels from a complete constituent picture.
- Quantum-number assignment
- electric charge in e; baryon number; spin J in units of ħ; parity P; charge-conjugation parity C where applicable; flavour quantum numbers Distinguishes states and constrains production and decay channels.
- Mass
- MeV/c² or GeV/c², with uncertainty and mass-definition convention Supports identification and kinematic checks; resonance mass definitions must remain distinguishable.
- Lifetime or total decay width
- s for lifetime; MeV or GeV for width; bound or measurement status Separates persistent particles from short-lived resonances and constrains observable signatures.
- Decay channel
- parent state → final-state particles, with branching fraction or limit and interaction attribution Connects identification evidence to allowed transformations.
- Spatial and electromagnetic structure
- mean-square charge radius in fm²; magnetic moment with explicit unit convention; form factors versus momentum transfer Records experimentally accessible structure without assigning every hadron a hard geometric boundary.
- Occurrence kinematics
- four-momentum with units and reference frame; polarisation where determined Supports event-level reconstruction without treating motion as a species property.
- Evidence status
- established | candidate | disputed | excluded within a stated analysis Keeps recognition and action proportional to the available evidence.
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 17 findings · 27 questions.
Identity and family Establishes what hadronic entity is being described and how it is classified.
Names, charge states, resonances and individual detections must resolve to the correct referent.
Referent and naming
Separates a hadron species from an occurrence or candidate signal.
Hadron referent
Record the identity, aliases and referent level before attaching physical properties.
- Does this record describe a hadron species, one occurrence or a proposed resonance? definition
- Which naming authority or experimental report connects these aliases to the same state? provenance
Family and boundaries
Locates the entity within hadronic families and adjacent particle categories.
Family assignment
Record baryon number and family assignment independently of electric charge and spin statistics.
- What baryon number supports the baryon, antibaryon or meson assignment? definition
- What establishes this entity as a single hadronic state rather than a nucleus, unbound particle pair or nonhadronic particle? boundary
QCD structure Records flavour content and evidence about the hadron's internal organisation.
A useful hadron model must distinguish constituent shorthand from a full or experimentally established description.
Flavour and colour
Captures flavour assignments and the colour-neutral nature of the state.
Constituent description
Separate valence-flavour notation from sea-quark and gluon contributions and from any proposed spatial arrangement.
- Which flavour content or flavour superposition is assigned, and which parts remain uncertain? definition
- Does the stated quark content express a minimal valence assignment or a claim about the full internal structure? boundary
Structure interpretations
Preserves competing accounts of conventional, multiquark, molecular or gluonic structure.
Interpretation evidence
Attach internal-structure interpretations to the observations and theoretical assumptions supporting them.
- Which measurements discriminate among the proposed internal-structure interpretations? measurement
- Which interpretations follow from data directly, and which depend on a particular theoretical calculation or fit? provenance
Quantum and intrinsic properties Describes the state through quantum numbers and measurable intrinsic properties.
Hadron identification and reaction constraints depend on these properties and their conventions.
Quantum-state assignment
Records measured or proposed spin, discrete symmetries and flavour quantum numbers.
Applicable quantum numbers
Distinguish established assignments, competing assignments and quantum numbers that do not apply.
- What electric charge, spin, parity and flavour quantum numbers are assigned to this state? definition
- Is charge-conjugation parity defined for this state, and what evidence supports any quoted assignment? boundary
Mass and probed structure
Captures mass and structure observables with uncertainties and measurement definitions.
Intrinsic observables
Record mass, radii, moments and form factors only with the conventions needed to interpret them.
- What mass and uncertainty are reported, and is the value a pole parameter, a line-shape parameter or another specified quantity? measurement
- Which radius, moment or form-factor observables have been measured, at what momentum transfer and with which units? measurement
Production, interaction and decay Describes how the hadron is produced, interacts and transforms.
An agent needs process-specific constraints to interpret observations and assess proposed reactions.
Production and scattering
Links reaction channels to energy, environment and measured interaction behaviour.
Reaction conditions
Record the initial state, collision energy and conditions attached to production or scattering observations.
- In which reactions and energy ranges has this hadron been produced or observed scattering? provenance
- Is a proposed reaction kinematically possible and compatible with the conservation rules of the specified interaction? action
Stability and decay
Connects lifetime, width and decay channels to their physical and observational context.
Decay behaviour
Distinguish measured decay, experimental limits and stability claims with explicitly stated conditions.
- What lifetime or total width is measured or bounded, and does the statement concern a free hadron or one in a bound environment? measurement
- Which decay channels and branching fractions are established, and which interaction governs each channel? provenance
Recognition and evidence Connects physical identity to observable signatures and the strength of the supporting evidence.
Many hadrons are inferred through decay products or resonance analyses, making identification quality part of the model.
Observable signatures
Specifies how an occurrence can be reconstructed or distinguished from alternatives.
Identification path
Record the measurements and reconstruction assumptions used to identify the hadron.
- Which tracks, decay vertices, energy deposits, missing quantities or reconstructed final states support this identification? measurement
- Which additional observation would best distinguish this assignment from a nearby hadron state or background process? action
State establishment
Assesses whether an observation supports a distinct hadronic state.
Resonance evidence status
Keep observed enhancements, resonance interpretations and established identities separate.
- What analysis supports a distinct state rather than a threshold effect, reflection or background fluctuation? provenance
- Which independent observations support the assignment, and which disagreements remain unresolved? 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.
- No sources were consulted; numerical values are approximate recalled examples, not limits for all hadrons.
- Individual exotic-hadron internal structures can remain disputed, particularly compact multiquark versus hadronic-molecule interpretations.
- Free-neutron lifetime measurements differ between experimental methods; precision work should check current evaluations.
- Which of these check these first hold for the sense of hadron this model covers, and on what evidence? provenance
Kinds and varieties
Recalled without web access and unsourced; every item is a lead to verify.
- Baryons, including protons and neutrons
- Antibaryons
- Mesons, including pions and kaons
- Exotic hadrons with structures beyond conventional three-quark baryons and quark-antiquark mesons
- Which of these kinds and varieties hold for the sense of hadron 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 - Proton: 2212; neutron: 2112; positive pion: 211; neutral pion: 111 - Codes identify particle species, not individual particles; hadron is an umbrella category.
- Which of these identifiers and schemes hold for the sense of hadron this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Protons and neutrons constitute ordinary atomic nuclei.
- Proton beams are used in particle therapy for cancer.
- Hadron collisions probe the strong interaction and other fundamental physics.
- Neutron scattering investigates material structure and dynamics.
- Hadrons participate in cosmic-ray air showers.
- Which of these real-world use hold for the sense of hadron this model covers, and on what evidence? provenance
Typical measurements
Recalled without web access and unsourced; every item is a lead to verify.
- Rest mass of representative light hadrons - Approximately 135-140 for pions and 938-940 for protons and neutrons - MeV/c²
- Proton electric charge radius - Approximately 0.84 - fm
- Free-neutron mean lifetime - Approximately 880 - s
- Which of these typical measurements hold for the sense of hadron 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.
- Many hadrons are unstable and decay; this is intrinsic particle behaviour rather than mechanical failure.
- Energetic hadron radiation can damage biological tissue.
- Hadron interactions can produce secondary radiation and activate materials.
- Energetic hadrons can damage detectors and electronics or cause single-event upsets.
- Which of these failure modes and hazards hold for the sense of hadron 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.
- quark - A quark is an elementary colour-charged constituent; a hadron is a colour-neutral composite.
- lepton - A lepton is an elementary particle that does not carry colour charge; a hadron has strongly interacting constituents.
- atomic nucleus - A nucleus is a bound system of protons and neutrons; its constituent nucleons are hadrons, although a hydrogen-1 nucleus is itself one proton.
- baryon - A baryon is a hadron with baryon number +1; hadrons also include antibaryons and mesons.
- boson - Boson classifies particles by integer spin and statistics; hadron classifies their composite strong-interaction structure, encompassing both bosons and fermions.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of hadron this model covers, and on what evidence? provenance
What the second pass must settle
- Which authoritative particle listings and review criteria should govern established, candidate and disputed status in this registry?
- How should the registry link glueball, hybrid and hadronic-molecule candidates to hadron without treating contested structural interpretations as settled identities?
- Where should the registry draw the operational boundary between a hadronic molecular state and a nuclear bound system?
- Which conventions should be required when comparing broad or overlapping resonance masses and widths?
- Should medium-modified hadron properties be represented as contextual states here or delegated to a separate model of the surrounding matter?