Exotic molecular states and tetraquark states with J^P =0⁺, 1⁺, 2⁺ *

Abstract

We have calculated the mass spectra for the molecular states and tetraquark states with . The masses of the axial-vector , molecular states and , tetraquark states are predicted to be approximately 3.98 GeV, in good agreement with the mass of from BESIII. In both the molecular and diquark-antidiquark scenarios, our results suggest that there may exist two almost degenerate states, as the strange partners of and . We propose to carefully examine in future experiments to verify this. One may also search for more hidden-charm four-quark states with strangeness in not only the open-charm channels but also the hidden-charm channels , .

Possible triply heavy tetraquark states

“…The result led some theorists to doubt whether the X(5568) is a genuine resonance [20][21][22]. In 2020, the BESIII Collaboration had observed a new signal, the Z cs (3985) − , in the K + recoil-mass spectrum in the process e + e − −→ K + (D − s D * 0 + D * − s D 0 ) at the center of mass energy √ 4.681 GeV [23], so the Z cs state, which lies near the D − s D * 0 and D * − s D 0 thresholds, had been predicted in several theoretical models [24][25][26][27][28][29][30]. But the nature of Z cs (3985) remains elusive.…”

The decay widths of the $Z_{cs}(3985/4000)$ based on rigorous quark-hadron duality

“…In the QCD sum rules, we usually choose the color antitriplet-triplet type and singlet-singlet type four-quark currents to interpolate the hidden-charm exotic states, and can reproduce the masses of the Z cs (3985/4000) both in the pictures of the tetraquark states [17,18,19,20] and molecular states [17,21,22,23,24]. There maybe exist two Z cs states, an antitriplet-triplet type tetraquark state and singlet-singlet type molecular state, or only one Z cs state, which has both the antitriplet-triplet type and singlet-singlet type components.…”

Impact of a thermal medium on newly observed $$Z_{cs}(3985)$$ resonance and its b-partner

“…This discovery could offer some unique hints to uncover the secrets of charged exotic Z structures. This new hadronic structure is assigned to the class of exotic state as the strange partner of Z c (3900) and studied in many different models in the literature in the molecular and tetraquark scenarios [15][16][17][18][19][20][21][22][23][24][25]. Its mass and width are defined in experiment as M Z cs = 3982.5 +1.8 −2.6 ± 2.1 MeV, Z cs = 12.8 +5.3 −4.4 ± 3.0 MeV.…”