Eur. Phys. J. C (2020) 80: 1026
https://doi.org/10.1140/epjc/s10052-020-08597-1

Regular Article - Theoretical Physics

Open-charm tetraquark $X_c$ and open-bottom tetraquark $X_b$

¹ Department of Physics, National Taiwan University, 10617, Taipei, Taiwan, ROC
² Physics Division, National Center for Theoretical Sciences, 30013, Hsinchu, Taiwan, ROC
³ INPAC, Shanghai Key Laboratory for Particle Physics and Cosmology, MOE Key Laboratory for Particle Physics, Astronomy and Cosmology, School of Physics and Astronomy, Shanghai Jiao Tong University, 200240, Shanghai, China
⁴ Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, 210023, Nanjing, Jiangsu, China
⁵ Nuclear Science Division, Lawrence Berkeley National Laboratory, 94720, Berkeley, CA, USA

^c rlzhu@njnu.edu.cn

Received: 20 August 2020
Accepted: 23 October 2020
Published online: 6 November 2020

Abstract

Motivated by the LHCb observation of exotic states $X_{0,1}(2900)$ with four open quark flavors in the $D^{-}{K}^{+}$ invariant mass distribution in the decay channel $B^{\pm }\to D^{+}{D}^{-}{K}^{\pm }$, we study the spectrum and decay properties of the open charm tetraquarks. Using the two-body chromomagnetic interactions, we find that the two newly observed states can be interpreted as a radial excited tetraquark with $J^P=0^{+}$ and an orbitally excited tetraquark with $J^P=1^{-}$, respectively. We then explore the mass and decays of the other flavor-open tetraquarks made of $su\overline{d}\overline{c}$ and $ds\overline{u}\overline{c}$, which are in the $\overline{6}$ or 15 representation of the flavor SU(3) group. We point that these two states can be found through the decays: $X_{ds\overline{u}\overline{c}}^{(\prime )}\to (D^{-}{K}^{-},D_s^{-}{\pi }^{-})$, and $X_{su\overline{d}\overline{c}}^{(\prime )}\to D_s^{-}{\pi }^{+}$. We also apply our analysis to open bottom tetraquark $X_b$ and predict their masses. The open-flavored $X_b$ can be discovered through the following decays: $X_{ud\overline{s}\overline{b}}\to B^0{K}^{+}$, $X_{ds\overline{u}\overline{b}}^{(\prime )}\to (B^0{K}^{-},B_s^0{\pi }^{-})$, and $X_{su\overline{d}\overline{b}}^{(\prime )}\to B_s^0{\pi }^{+}$.