Physics:Theta meson

From HandWiki
Theta meson
Quark structure of the theta meson
Compositiontt
Statisticsbosonic
Interactionsstrong, weak, gravitational, electromagnetic
Statushypothetical
antiparticleself
electric charge0 e
Isospin0
Hypercharge0
Parity−1
C parity−1

The theta meson (θ)[1] is a hypothetical form of quarkonium (i.e. a flavourless meson) formed by a top quark (t) and top antiquark (t). As a P-odd and C-odd tt state, it is analogous to the ϕ (ss), J/ψ (cc) and ϒ (bb) mesons. Due to the top quark's short lifetime, the theta meson is expected to not be observed in nature.[2]

In 2025, new research from the CMS[3] and ATLAS[4] collaborations demonstrated the existence of theta mesons at greater than 5-sigma significance.[5][6]

See also

References

  1. ↑ Roos, M.; Wohl, C.G.. "Naming Scheme for Hadrons". http://pdg.lbl.gov/2014/reviews/rpp2014-rev-naming-scheme-hadrons.pdf. 
  2. ↑ Fabiano, N. (1998). "Top mesons". European Physical Journal C 2 (2): 345–350. doi:10.1007/s100520050144. Bibcode: 1998EPJC....2..345F. 
  3. ↑ CMS Collaboration (2025). "Observation of a pseudoscalar excess at the top quark pair production threshold". Reports on Progress in Physics 88 (8). doi:10.1088/1361-6633/adf7d3. PMID 40763770. Bibcode: 2025RPPh...88h7801C. 
  4. ↑ ATLAS Experiment. "Observation of a cross-section enhancement near the tt‾ threshold in s=13 TeV pp collisions with the ATLAS detector". https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2025-008/. 
  5. ↑ Siegel, Ethan (9 July 2025). "Starts With A Bang: The top quark isn't a loner after all: "toponium" is real!". https://bigthink.com/starts-with-a-bang/top-quark-loner-toponium/. 
  6. ↑ "Elusive romance of top-quark pairs observed at the LHC". https://home.cern/news/press-release/physics/elusive-romance-top-quark-pairs-observed-lhc. 




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