# List of mesons

A meson is a hadron composed of one quark and one antiquark, giving it baryon number 0 and integer spin, so every meson is a boson.<sup>[1](https://repository.cern/records/yce42-d5344/files/fulltext.pdf?download=1)</sup> The standard reference list is the Meson Summary Table of the Particle Data Group (PDG), published each year in the *Review of Particle Physics*; the 2024 edition, S. Navas et al., *Phys. Rev. D* **110**, 030001, has a cut-off date of January 15, 2024, and the 2025 update extends it to January 15, 2025.<sup>[2](https://pdg.lbl.gov/2024/tables/contents_tables_mesons.html)</sup><sup> • </sup><sup>[3](https://pdg.lbl.gov/2025/tables/contents_tables_mesons.html)</sup>

| Key fact | Detail |
|---|---|
| Definition | Hadron made of one quark and one antiquark; baryon number 0; integer spin, hence a boson<sup>[1](https://repository.cern/records/yce42-d5344/files/fulltext.pdf?download=1)</sup> |
| Reference list | PDG Meson Summary Table, *Phys. Rev. D* **110**, 030001 (2024) and 2025 update<sup>[2](https://pdg.lbl.gov/2024/tables/contents_tables_mesons.html)</sup> |
| Table categories | Nine groups: light unflavored, strange, charmed, charmed-strange, bottom, bottom-strange, bottom-charmed, c c̄, and b b̄<sup>[4](https://pdg.lbl.gov/2024/booklet/sum-tab-mesons.html)</sup> |
| Lightest meson | Charged pion: mass 139.57039 ± 0.00018 MeV, mean life (2.6033 ± 0.0005) × 10⁻⁸ s<sup>[5](https://pdg.lbl.gov/2025/tables/rpp2025-sum-mesons.pdf)</sup> |
| Established strange mesons | The PDG lists 25 strange mesons, 9 of which still need confirmation (2022 edition)<sup>[6](https://arxiv.org/abs/2310.09249)</sup> |
| Exotic entry | π₁(1600), with quantum numbers forbidden for a quark-model state, has solid experimental evidence from COMPASS<sup>[7](https://arxiv.org/abs/1909.06366)</sup> |
| Non-qq̄ naming | Since the 2024 edition, tetraquark mesons carry the base name T and pentaquark baryons P<sup>[8](https://pdg.lbl.gov/2025/reviews/rpp2025-rev-naming-scheme-hadrons.pdf)</sup> |

## How the list is organized

The PDG divides mesons by flavor quantum numbers. The 2024 booklet lists nine sections: light unflavored mesons with S = C = B = 0, strange mesons with S = ±1, charmed mesons with C = ±1, charmed-strange mesons with C = S = ±1, bottom mesons with B = ±1, bottom-strange and bottom-charmed mesons, and the hidden-flavor c c̄ and b b̄ systems, each including possibly non-q q̄ states.<sup>[4](https://pdg.lbl.gov/2024/booklet/sum-tab-mesons.html)</sup> Within the light unflavored section the isovector families carry the base symbols π, b, ρ, and a, while the isoscalar families are η, h, ω, φ, and f; the c c̄ states are ηc, hc, ψ, and χc, and the b b̄ states ηb, hb, Υ, and χb.<sup>[8](https://pdg.lbl.gov/2025/reviews/rpp2025-rev-naming-scheme-hadrons.pdf)</sup>

A bullet in the quark-content table marks particles that appear in the preceding Meson Summary Table; the PDG states it does not regard the other entries as established.<sup>[9](https://pdg.lbl.gov/2025/tables/rpp2025-qtab-mesons.pdf)</sup> The mass in parentheses in a name such as ρ(770) is fixed when the name is assigned and is revised case by case as better measurements arrive.<sup>[8](https://pdg.lbl.gov/2025/reviews/rpp2025-rev-naming-scheme-hadrons.pdf)</sup>

## Representative entries

**Light unflavored mesons.** The established low-mass entries include π± and π0, η, f₀(500), ρ(770), ω(782), η′(958), f₀(980), a₀(980), and φ(1020), followed by orbital and radial excitations such as a₁(1260), f₂(1270), a₂(1320), and, at higher masses, states like f₄(2050) and f₆(2510).<sup>[9](https://pdg.lbl.gov/2025/tables/rpp2025-qtab-mesons.pdf)</sup> The charged pion is the lightest meson on the list, with a mass of 139.57039 ± 0.00018 MeV and a mean life of (2.6033 ± 0.0005) × 10⁻⁸ s.<sup>[5](https://pdg.lbl.gov/2025/tables/rpp2025-sum-mesons.pdf)</sup>

**Strange mesons.** The strange section runs from the pseudoscalar kaons K±, K0, K0S, and K0L through K*(892) and the K* multiplets up to K*5(2380) and K4(2500), with a K(3100) of unknown quantum numbers at the end.<sup>[9](https://pdg.lbl.gov/2025/tables/rpp2025-qtab-mesons.pdf)</sup> As of the 2022 edition the PDG listed 25 strange mesons, 9 of which still needed confirmation, and many states predicted by quark models were missing.<sup>[6](https://arxiv.org/abs/2310.09249)</sup>

**Charmed and bottom mesons.** The charmed section lists D±, D0, D*(2010)±, D*(2007)0, and excited states through D(3000); the charmed-strange section runs from Ds± and D*s± through D*s3(2860)±.<sup>[9](https://pdg.lbl.gov/2025/tables/rpp2025-qtab-mesons.pdf)</sup> The bottom section contains B±, B0, B*, B₁(5721), B*2(5747), and BJ(5970), the bottom-strange section B0s through BsJ(6114), and the bottom-charmed section B+c and B(2S)±.<sup>[9](https://pdg.lbl.gov/2025/tables/rpp2025-qtab-mesons.pdf)</sup>

**Hidden-flavor mesons.** The c c̄ (charmonium) list begins with ηc(1S) and J/ψ(1S), the ground state and radial excitations of the charm-anticharm system, both carrying the photon's quantum numbers J = 1, P = −1, C = −1 for the vector states.<sup>[9](https://pdg.lbl.gov/2025/tables/rpp2025-qtab-mesons.pdf)</sup><sup> • </sup><sup>[10](https://atlas.cern/Glossary/jpsi-meson)</sup> The discovery of the J/ψ in 1974 and its identification as charmonium led to a broad rethinking of particle physics.<sup>[11](https://atlas.cern/updates/briefing/mesons-and-bosons)</sup> The b b̄ (bottomonium) list runs from ηb(1S) and Υ(1S) through Υ(11020).<sup>[9](https://pdg.lbl.gov/2025/tables/rpp2025-qtab-mesons.pdf)</sup> No t t̄ state is named, because the top quark decays so rapidly that bound-state hadrons containing it are unlikely to exist.<sup>[12](https://pdg.lbl.gov/2025/reviews/rpp2025-rev-quark-model.pdf)</sup>

## Non-qq̄ entries and the naming scheme

The list is no longer confined to quark-antiquark states. The χc1(3872), also known as X(3872), was discovered by Belle in 2003 in B± → K±X decays and triggered extensive searches for states beyond the standard q q̄ model in the charm and bottom sectors.<sup>[13](https://pdgweb.lbl.gov/2025/reviews/rpp2025-rev-non-qqbar-mesons.pdf)</sup> The 2024 edition introduced a new naming scheme for the many recently discovered mesons and baryons with c or b quarks that are not compatible with conventional q q̄ or qqq structures, placing them in an "Other mesons" section.<sup>[14](https://pdg.lbl.gov/2024/reviews/rpp2024-rev-highlights.pdf)</sup> Under the current scheme the base name T is used when the minimal quark content is q q̄ q̄ ([tetraquark](https://www.edgepedia.org/tetraquark)) and P when it is q q q q q̄ (pentaquark), with the heavy-quark content listed as a subscript.<sup>[8](https://pdg.lbl.gov/2025/reviews/rpp2025-rev-naming-scheme-hadrons.pdf)</sup> [The Other](https://www.edgepedia.org/the-other) mesons table now includes states such as T*ss0(2870), Tcc(3875)+, Tψ1(3900), T*cs1(2900), and Tψ0(6900).<sup>[9](https://pdg.lbl.gov/2025/tables/rpp2025-qtab-mesons.pdf)</sup>

**Exotic quantum numbers.** Some listed states cannot be q q̄ at all. In the quark model, mesons with natural spin-parity and CP = −1, such as 0⁺⁻, 1⁻⁺, and 2⁺⁻, are forbidden, as is JPC = 0⁻⁻.<sup>[12](https://pdg.lbl.gov/2025/reviews/rpp2025-rev-quark-model.pdf)</sup> The π₁(1400) and π₁(1600), which carry the forbidden 1⁻⁺ quantum numbers, were merged into the same node in the 2024 edition, and COMPASS data provide solid evidence for the π₁(1600) as well as for the a₁(1420), which does not fit the quark-model spectrum.<sup>[14](https://pdg.lbl.gov/2024/reviews/rpp2024-rev-highlights.pdf)</sup><sup> • </sup><sup>[7](https://arxiv.org/abs/1909.06366)</sup>

## How the list is maintained

The PDG collects, evaluates, and averages measured properties from refereed journals; the 2024 edition incorporated 2,717 new measurements from 869 papers alongside data from previous editions.<sup>[15](https://cds.cern.ch/record/2907603?ln=en)</sup> The 2024 meson-resonance update included new cross-particle fits involving J/ψ(1S), ψ(2S), and ηc(1S), listing of complex pole positions when available, and the addition of several newly established mesons to the Summary Tables.<sup>[14](https://pdg.lbl.gov/2024/reviews/rpp2024-rev-highlights.pdf)</sup> Experimental input comes from spectroscopy programs such as [BESIII](https://www.edgepedia.org/besiii), which has studied light mesons through charmonium decays at center-of-mass energies of 2.0 to 4.6 GeV for nearly three decades, and COMPASS, which scatters a 190 GeV/c pion beam off proton and nuclear targets.<sup>[16](https://doi.org/10.1093/nsr/nwab198)</sup><sup> • </sup><sup>[7](https://arxiv.org/abs/1909.06366)</sup>

## References

1. [1.2.1 Mesons, CERN document repository](https://repository.cern/records/yce42-d5344/files/fulltext.pdf?download=1)
2. [2024: Mesons Summary Tables, Particle Data Group](https://pdg.lbl.gov/2024/tables/contents_tables_mesons.html)
3. [2025: Summary Tables, Particle Data Group](https://pdg.lbl.gov/2025/tables/contents_tables_mesons.html)
4. [PDG Summary Tables: Mesons (2024 booklet)](https://pdg.lbl.gov/2024/booklet/sum-tab-mesons.html)
5. [rpp2025-sum-mesons.pdf, Particle Data Group](https://pdg.lbl.gov/2025/tables/rpp2025-sum-mesons.pdf)
6. [Strange-Meson Spectroscopy with COMPASS (S. Wallner, arXiv:2310.09249)](https://arxiv.org/abs/2310.09249)
7. [Light-Meson Spectroscopy with COMPASS (arXiv:1909.06366)](https://arxiv.org/abs/1909.06366)
8. [8. Naming Scheme for Hadrons, Review of Particle Physics 2025](https://pdg.lbl.gov/2025/reviews/rpp2025-rev-naming-scheme-hadrons.pdf)
9. [Meson Summary Table (quark-content), rpp2025-qtab-mesons.pdf, Particle Data Group](https://pdg.lbl.gov/2025/tables/rpp2025-qtab-mesons.pdf)
10. [J/ψ meson, ATLAS Experiment glossary, CERN](https://atlas.cern/Glossary/jpsi-meson)
11. [Of mesons and bosons, ATLAS Experiment at CERN](https://atlas.cern/updates/briefing/mesons-and-bosons)
12. [15. Quark Model, Review of Particle Physics 2025](https://pdg.lbl.gov/2025/reviews/rpp2025-rev-quark-model.pdf)
13. [78. Heavy Non-qq̄ Mesons, Review of Particle Physics 2025](https://pdgweb.lbl.gov/2025/reviews/rpp2025-rev-non-qqbar-mesons.pdf)
14. [Highlights of the 2024 Edition of the Review of Particle Physics, Particle Data Group](https://pdg.lbl.gov/2024/reviews/rpp2024-rev-highlights.pdf)
15. [Review of particle physics, 2024–2025, CERN Document Server](https://cds.cern.ch/record/2907603?ln=en)
16. [Highlights of light meson spectroscopy at the BESIII experiment, National Science Review](https://doi.org/10.1093/nsr/nwab198)

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*Topic: Encyclopedia › Physical world and mathematics › Physics › Particles and nuclei › Particle physics › Hadrons and hadron spectroscopy › Hadrons overview*

*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 15, 2026 · Edited: Sep 30, 2026; Oct 15, 2026 · Last review: Oct 15, 2026*

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