Determination of the spin and parity of all-charm tetraquarks
Journal Article
Overview
abstract
Abstract; ; The traditional quark model; 1,2; 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; 3; . The exact nature of their internal structure remains uncertain; 4–29; . Here we report the first measurement of quantum numbers of the recently discovered family of three all-charm tetraquarks; 30–32; , using data collected by the CMS experiment at the Large Hadron Collider from 2016 to 2018 (refs. ; 33,34; ). The angular analysis techniques developed for the discovery and characterization of the Higgs boson; 35–37; 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 2; ħ; , while 0; ħ; and 1; ħ; are excluded at 95% and 99% confidence levels, respectively. The; J; ; P; C; ; = 2; ++; assignment implies particular configurations of constituent spins and orbital angular momenta, which constrain the possible internal structure of these tetraquarks.;
