Abstract
In the framework of QCD Sum Rules we investigate the $q q^\prime \bar{Q} \bar{Q}$ tetraquark structure with quantum number $J^P = 1^+$, which are embedded in two types of configurations, the $[8_c]_{q \bar{Q}} \otimes [8_c]_{q^\prime \bar{Q}}$ and $[1_c]_{q \bar{Q}} \otimes [1_c]_{q^\prime \bar{Q}}$ with $Q = b, c$, $q = u$, and $q^\prime = d, s$. Our finding confirms the Lattice QCD result that the bottom tetraquark states could exist and their masses are evaluated. In the calculation, the non-perturbative condensate contributions up to dimension eight in operator product expansion are considered, and those terms linear to the strange quark mass $m_s$ are kept. It is found that for octet-octet configuration the masses of potential tetraquark states are about $11.28$ GeV for the $ud\bar{b}\bar{b}$ system, and $11.31$ and $11.34$ GeV for the $us\bar{b}\bar{b}$ system, which are above the corresponding two-meson thresholds. For molecular configuration, the corresponding masses are found below the thresholds, that is $10.36$ GeV and $10.48$ GeV, respectively. The possible tetraquark decay channels are analyzed and the strong decay rates are evaluated. The mass dependence on the radiative correction and the condensates is estimated. Moreover, the doubly charmed tetraquark states are also considered.
Highlights
In the framework of quantum chromodynamics (QCD) and quark model, various hadron structures beyond the normal meson and baryon are yet rarely explored, like multiquark state, hybrid, glueball, etc., which are theoretically legitimate to exist but experimentally hard to identify
In the framework of QCD sum rules, we investigate the qq0Q Qtetraquark structure with quantum number JP 1⁄4 1þ, which is embedded in two types of configurations, the 1⁄28cqQ ⊗ 1⁄28cq0Qand 1⁄21cqQ ⊗ 1⁄21cq0Qwith Q 1⁄4 b, c, q 1⁄4 u, and q0 1⁄4 d, s
Heavy tetraquarks composed of two heavy antiquarks (Q Q ) and two light quarks, where Q 1⁄4 b, c and q 1⁄4 u, q0 1⁄4 d, s, are of peculiar interest in physics
Summary
In the framework of quantum chromodynamics (QCD) and quark model, various hadron structures beyond the normal meson and baryon are yet rarely explored, like multiquark state, hybrid, glueball, etc., which are theoretically legitimate to exist but experimentally hard to identify. The attraction force induced by the color Coulomb potential of two antiquarks in color 3c configuration enables the existence of stable qq0Q Qtetraquark states possible in the mQ → ∞ limit [3] The properties of such states were explored in depth in a variety of theories, such as the MIT bag model [4], color flux-tube model [5], chiral quark model [6,7], constituent quark model [8,9], chiral perturbation [10], and lattice QCD [11,12,13]. Employing the QCD sum rules, in recent years, people have performed some remarkable researches on exotic hadrons, including the doubly heavy tetraquark states [15,16,17,18]. We analyze in the framework of QCD sum rules whether there exists stable JP 1⁄4 1þ tetraquark state with coloroctet-octet configuration or not and calculate the doubly heavy molecular tetraquark state by means of currents given in Refs. The last part is left for conclusions and discussion of the results
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