Abstract
Inspired by the report of D0 Collaboration on the state $X(5568)$ with four different flavors, a similar state, $ud\bar{s}\bar{b}$ is investigated in the present work. The advantage of looking for this state over the state $X(5568)$ with quark contents, $bu\bar{d}\bar{s}$ or $bd\bar{u}\bar{s}$, is that the $BK$ threshold is 270 MeV higher than that of $B_s \pi$, and it allows a large mass region for $ud\bar{s}\bar{b}$ to be stable. The chiral quark model and Gaussian expansion method are employed to do the calculations of four-quark states $ud\bar{s}\bar{b}$ with quantum numbers $IJ^{P}$($I=0,1;~ J=0,1,2;~P=+$). Two structures, diquark-antidiquark and meson-meson, with all possible color configurations are considered. The results indicate that energies of the tetraquark with diquark-antiquark configuration are all higher than the threshold of $BK$, but for the state of $IJ^P=00^+$ in the meson-meson structure, the energies are below the corresponding thresholds, where the color channel coupling plays an important role. The distances between two objects (quark/antiquark) show that the state is a molecular one.
Highlights
Since the first exotic resonance Xð3872Þ was observed by the Bell Collaboration in 2003 [1], many other exotic states, so-called XYZ states, have emerged from the reports of Belle, BABAR, BESIII, LHCb, CDF, D0, and other collaborations
In order to look for the particle of Tbs theoretically, we calculate the masses of the states with quantum numbers IJP (I 1⁄4 0; 1; J 1⁄4 0; 1; 2; P 1⁄4 þ), including two different structures, diquark-antidiquark and meson-meson in the chiral quark model, and all possible color configurations are investigated by using the Gaussian expansion method (GEM) [21]
We try to look for the particle with quantum numbers IJPðI 1⁄4 0; 1; J 1⁄4 0; 1; 2; P 1⁄4 þ) consisting of four different flavors udsb, denoted as Tbs, in the chiral quark model
Summary
Since the first exotic resonance Xð3872Þ was observed by the Bell Collaboration in 2003 [1], many other exotic states, so-called XYZ states, have emerged from the reports of Belle, BABAR, BESIII, LHCb, CDF, D0, and other collaborations. Our previous quark model calculation of diquark-antidiquark states and molecules obtained negative results [19]. In this work, another particle with four different flavors, udsb ̄ , which is different from Xð5568Þ consisting of usdb ̄ , is considered. In order to look for the particle of Tbs theoretically, we calculate the masses of the states with quantum numbers IJP (I 1⁄4 0; 1; J 1⁄4 0; 1; 2; P 1⁄4 þ), including two different structures, diquark-antidiquark and meson-meson in the chiral quark model, and all possible color configurations are investigated by using the Gaussian expansion method (GEM) [21].
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