The Tetraquark System in a Chiral Quark Model
Gang Yang (Department of Physics, Zhejiang Normal University, Jinhua 321004, China); Jialun Ping (Department of Physics and Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems, Nanjing Normal University, Nanjing 210023, China); Jorge Segovia (Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, E-41013 Sevilla, Spain)
The S-wave $ \bar{q}q\bar{s}Q \;\; (q=u,\,d;\,Q=c,\,b) $ tetraquarks, with spin-parities $ \bar{q}q\bar{s}Q \;\; (q=u,\,d;\,Q=c,\,b) $ , $ \bar{q}q\bar{s}Q \;\; (q=u,\,d;\,Q=c,\,b) $ , and $ \bar{q}q\bar{s}Q \;\; (q=u,\,d;\,Q=c,\,b) $ , in both isoscalar and isovector sectors, are systematically studied using a chiral quark model. The meson-meson, diquark-antidiquark, and K-type arrangements of quarks and all possible color wave functions are comprehensively considered. The four-body system is solved using the Gaussian expansion method, a highly efficient computational approach. Additonally, a complex-scaling formulation of the problem is established to disentangle bound, resonance, and scattering states. This theoretical framework has already been successfully applied in various tetra- and penta-quark systems. For the complete coupled channel and within the complex-range formulation, several narrow resonances of $ \bar{q}q\bar{s}Q \;\; (q=u,\,d;\,Q=c,\,b) $ and $ \bar{q}q\bar{s}Q \;\; (q=u,\,d;\,Q=c,\,b) $ systems are obtained, in each allowed $ \bar{q}q\bar{s}Q \;\; (q=u,\,d;\,Q=c,\,b) $ -channel, within the energy regions of $ \bar{q}q\bar{s}Q \;\; (q=u,\,d;\,Q=c,\,b) $ GeV and $ \bar{q}q\bar{s}Q \;\; (q=u,\,d;\,Q=c,\,b) $ GeV, respectively. The predicted exotic states, which indicate a richer color structure when going towards multiquark systems beyond mesons and baryons, are expected to be confirmed in future high-energy particle and nuclear experiments.