NEWS AND VIEWS
03 December 2025 Quarks in ‘exotic’ quartets prefer to stick together Evidence of a particle made up of four tightly bound quarks tests physicists’ understanding of the force that holds protons and neutrons together. By Elena Santopinto ORCID: http://orcid.org/0000-0003-3942-6554 0 Elena Santopinto Elena Santopinto is in the Sezione di Genova at the Istituto Nazionale di Fisica Nucleare (INFN), Genoa 16146, Italy. View author publications PubMed Google Scholar
Protons and neutrons, which are the building blocks of atomic nuclei, are made up of triplets of fundamental particles called quarks. Composite particles formed from quarks are known as hadrons, and can also contain pairs of quarks. Over the past two decades, evidence has accumulated that the hadron family includes ‘exotic’ states made up of four or five quarks. However, scientists disagree over whether exotic states are combinations of standard two- and three-quark hadrons or constitute a single compact object. Now, writing in Nature, the Compact Muon Solenoid (CMS) Collaboration1 reports a measurement of the properties of a type of exotic, four-quark hadron called a tetraquark, which favours the latter interpretation.
Nature 648, 48-49 (2025)
doi: https://doi.org/10.1038/d41586-025-03591-7
References The CMS Collaboration. Nature 648, 58–63 (2025). LHCb Collaboration. Sci. Bull. 65, 1983–1993 (2020). ATLAS Collaboration. Phys. Rev. Lett. 131, 151902 (2023). CMS Collaboration. Phys. Rev. Lett. 132, 111901 (2024). Gell-Mann, M. Phys. Lett. 8, 214–215 (1964). Zweig, G. Report No. CERN-TH-412 (CERN, 1964). Bolognesi, S. et al. Phys. Rev. D 86, 095031 (2012). Becchi, C., Ferretti, J., Giachino, A., Maiani, L. & Santopinto, E. Phys. Lett. B 811, 13592 (2020). Belov, I., Giachino, A. & Santopinto, E. J. High Energy Phys. 2025, 93 (2025). Download references
Competing Interests The author declares no competing interests.
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