Authors: Aram Hayrapetyan | Vladimir Makarenko | A. Tumasyan | Wolfgang Adam | Janik Walter Andrejkovic | L. Benato | T. Bergauer | M. Dragicevic | C. Giordano | Priya Sajid Hussain | Manfred Jeitler | Natascha Krammer | A. Li | Dietrich Liko | Mark Matthewman | Ivan Mikulec | J. Schieck | Robert Schöfbeck | Dennis Schwarz | Maryam Shooshtari | M. Sonawane | W. Waltenberger | Claudia-Elisabeth Wulz | X. Janssen | Hyejin Kwon | Daniel Ocampo Henao | T. Van Laer | Pierre van Mechelen | Jas Bierkens | Nordin Breugelmans | Jorgen d'Hondt | Soumya Dansana | A. De Moor | M. Delcourt | Felix Heyen | Y. Hong | Pavlo Kashko | Steven Lowette | I. Makarenko | D. Müller | Juhee Song | Stefaan Tavernier | M. Tytgat | G. P. Van Onsem | S. Van Putte | D. Vannerom | Bugra Bilin | Barbara Clerbaux | Aloke Kumar Das | Isabelle de Bruyn | G. De Lentdecker | Hugues Evard | Laurent Favart | P. Gianneios | Ali Khalilzadeh | Fakhri Alam Khan | A. Malara | Muhammad Aamir Shahzad | Laurent Thomas | M. Vanden Bemden | C. Vander Velde | P. Vanlaer | Fengwangdong Zhang | M. De Coen | Didar Dobur | G. Gökbulut | J. Knolle | Luka Lambrecht | David Marckx | K. Skovpen | N. Van Den Bossche | Jan van der Linden | Jules Vandenbroeck | Liam Wezenbeek | Samuel Bein | A. Benecke | Agni Bethani | G. Bruno | A. Cappati | J. De Favereau De Jeneret | C. Delaere | A. Giammanco | Ahmet Oguz Guzel | Vincent Lemaître | J. Lidrych | Paul Malek | Paola Mastrapasqua | S. Turkcapar | G. A. Alves | M. Barroso Ferreira Filho | E. Coelho | Carsten Hensel | T. Menezes De Oliveira | C. Mora Herrera | P. Rebello Teles | Mariana Soeiro | E. J. Tonelli Manganote | A. Vilela Pereira | Walter Luiz Aldá Júnior | Helena Brandao Malbouisson
Source: Nature (article, 2025-12-03)
Field: Chemistry — Spectroscopy

Determination of the spin and parity of all-charm tetraquarks The traditional quark model<sup>1,2</sup> accounts for the existence of baryons, such as protons and neutrons, which consist of three quarks, as well as mesons, composed of a quark-antiquark pair. Only recently has substantial evidence started to accumulate for exotic states composed of four or five quarks and antiquarks<sup>3</sup>. The exact nature of their internal structure remains uncertain<sup>4-29</sup>. Here we report the first measurement of quantum numbers of the recently discovered family of three all-charm tetraquarks<sup>30-32</sup>, using data collected by the CMS experiment at the Large Hadron Collider from 2016 to 2018 (refs. <sup>33,34</sup>). The angular analysis techniques developed for the discovery and characterization of the Higgs boson<sup>35-37</sup> have been applied to the new exotic states. Here we show that the quantum numbers for parity P and charge conjugation C symmetries are found to be +1. The spin J of these exotic states is determined to be consistent with 2ħ, while 0ħ and 1ħ are excluded at 95% and 99% confidence levels, respectively. The J<sup>PC</sup> = 2<sup>++</sup> assignment implies particular configurations of constituent spins and orbital angular momenta, which constrain the possible internal structure of these tetraquarks. Parity (physics) ; Quantum number ; Spins ; Quark ; Spin (aerodynamics) ; Hadron ; Higgs boson ; Homogeneous space ; Quantum Molecular spectroscopy and chirality ; Magnetism in coordination complexes ; Advanced NMR Techniques and Applications