Open-charm tetraquark X_c and open-bottom tetraquark X_b

Xiao-Gang He,Ruilin Zhu,Wei Wang

doi:10.1140/epjc/s10052-020-08597-1

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 rightarrow 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 {bar{d}} {bar{c}} and d s {bar{u}} {bar{c}}, which are in the {bar{6}} or 15 representation of the flavor SU(3) group. We point that these two states can be found through the decays: X^{(prime )}_{d s bar{u}bar{c}}rightarrow (D^- K^-, D_s^- pi ^-) , and X^{(prime )}_{s u bar{d}bar{c}}rightarrow 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{bar{s}}bar{b}}rightarrow B^0K^+, X^{(prime )}_{d s bar{u}bar{b}}rightarrow (B^0 K^-, B_s^0 pi ^-) , and X^{(prime )}_{s u bar{d}bar{b}}rightarrow B_s^0pi ^+ .

Highlights

Very recently, the LHCb collaboration has reported an intriguing and important discovery of two exotic structures with open quark flavors in the invariant mass distribution of D− K + of the channel B± → D+ D− K ± [1,2,3]
M X0(2900) = 2.866 ± 0.007 ± 0.002 GeV, X0(2900) = 57 ± 12 ± 4 MeV, a e-mail: hexg@phys.ntu.edu.tw b e-mail: wei.wang@sjtu.edu.cn c e-mail: rlzhu@njnu.edu.cn while the broader one is called X1(2900) and has m X1(2900) = 2.904 ± 0.005 ± 0.001 GeV, X1(2900) = 110 ± 11 ± 4 MeV. These two structures are 502 MeV and 540 MeV higher than the D K threshold, respectively. Both of them can strongly decay into D− K + and have the minimum quark content [udsc]
In 2016 the D0 collaboration reported an open flavor state X (5568) decaying into Bs0π [4] but such a state is not confirmed by other experiments such as LHCb [5], CMS [6], CDF [7] and ATLAS [8]

Summary

Introduction

The LHCb collaboration has reported an intriguing and important discovery of two exotic structures with open quark flavors in the invariant mass distribution of D− K + of the channel B± → D+ D− K ± [1,2,3]. In the following we will carry out a calculation of the masses for these open-charm tetraquarks, and the corresponding open bottom multiplets Xb. We will use flavor SU(3) symmetry to study related strong two body hadronic decays and give some relations of decay widths among different decay channels, which may provide some guidances for experimental searches.

Results

Conclusion