Related papers: QCD Inequalities and the $D_s(2320)$
Recent investigations have suggested that the six-quark combination uuddss could be a deeply bound state (S) that has eluded detection so far, and a potential dark matter candidate. We report the first search for a stable, doubly strange…
We study the experimental $DK$ invariant mass spectra of the reactions $B^+ \to \bar{D}^0 D^0 K^+$, $B^0 \to D^- D^0 K^+$ (measured by the BaBar Collaboration) and $B_s \to \pi^+ \bar{D}^0 K^-$ (measured by the LHCb Collaboration), where an…
We discuss the possible existence of the fully-heavy tetraquarks. We calculate the ground-state energy of the $bb \bar b \bar b$ bound state, where $b$ stands for the bottom quark, in a nonrelativistic effective field theory framework with…
The question of whether there exist bound states of two heavy quarks $Q=(c,b)$ and antiquarks $\bar Q = (\bar c, \bar b)$, distinct from a pair of quark-antiquark mesons, has been debated for more than forty years. We suggest some means of…
The possibility of $QQ\bar{q}\bar{q}$ heavy-light four-quark bound states has been analyzed by means of the chiral SU(3) quark model, where $Q$ is the heavy quark ($c$ or $b$) and $q$ is the light quark ($u$, $d$ or $s$). We obtain a bound…
Very recently, the LHCb Collaboration observed distinct structures with the $cc\bar{c}\bar{c}$ in the $J/\Psi$-pair mass spectrum. In this work, we construct four scalar ($J^{PC} = 0^{++}$) $[8_c]_{Q\bar{Q^\prime}}\otimes [8_c]_{Q^\prime…
In this work, we study the $D\bar{D}$, $DD$, $D\bar{D}_s$, $DD_s$, $D_s\bar{D}_s$ and $D_sD_s$ tetraquark molecular states with the $J^{PC}=0^{++}$ via the QCD sum rules. The prediction $M_{D_s\bar {D}_s} = 3.98\pm0.10\, \rm{GeV}$ is in…
We explore molecular states of two open heavy-quark mesons (Q qbar)-(qbar Q) in a quark-based model in terms of a four-body non-relativistic Hamiltonian with pairwise effective interactions. Molecular states are found in the combinations of…
We present our recent results on antiheavy-antiheavy-light-light tetraquark systems using lattice QCD. Our study of the $ \bar{b}\bar{b}us $ four-quark system with quantum numbers $ J^P=1^+ $ and the $ \bar{b}\bar{c}ud $ four-quark systems…
The experimental status concerning the two new narrow states with charm-strange content is reviewed. The states have masses of 2317 and 2460 MeV, widths less than 10 MeV, isospin consistent with zero, and spin-parities consistent with being…
We study the mass of the state Y(2175) of J^{PC} = 1^{--} in the QCD sum rule. We construct both the diquark-antidiquark currents (ss)(s_bar s_bar) and the meson-meson currents (s_bar s)(s_bar s). We find that there are two independent…
We develop a moment QCD sum rule method augmented by fundamental inequalities to study the existence of exotic doubly hidden-charm/bottom tetraquark states made of four heavy quarks. Using the compact diquark-antidiquark configuration, we…
We present a search for the possible $I(J^{P})=0(2^{+})$ tetraquark state with $ss{\bar s}{\bar s}$ quark content in quenched improved anisotropic lattice QCD. Using various local and non-local interpolating fields we determine the energies…
We discuss the structure of the narrow mesons with charm and strangeness $D_{sJ}^*(2317)$ and $D_{sJ}(2460)$, stressing the role of the radiative decay modes in shedding light on the quark content of these states. We argue that present…
Recently, a charmonium $X(3960)$ in $B$ decays in the $D_s^+D_s^-$ invariant-mass spectrum is discovered by the LHCb Collaboration with the quantum number $J^{PC}=0^{++}$. Motivated by the discovery, in this work, we systematically…
Inspired by $\Xi_{cc}$ reported by LHCb Collaboration and $X(5568)$ reported by $D0$ Collaboration, the $QQ\bar{q}\bar{q}$ ($Q=c,b,s$, $q=u,d$) tetraquark states, are studied in the present work. With the help of gaussian expansion method,…
The pentaquark state recently discovered has been discussed based on various quark model calculations. Odd parity for the state can not be ruled out theoretically because contributions related to non-trivial color structures have not been…
We use QCD sum rules to test the nature of the recently observed mesons Y(4260), Y(4350) and Y(4660), assumed to be exotic four-quark $(c\bar{c}q\bar{q})$ or $(c\bar{c}s\bar{s})$ states with $J^{PC}=1^{--}$. We work at leading order in…
The recent experimental results of LHCb collaboration suggested the existence of pentaquark states with charmonium. To understand the structure of the states, a dynamical calculation of 5-quark systems with quantum numbers…
We study $D_s^+ D_s^-$ and $D \bar D$ states assuming that they are hadronic molecules with $J^{PC}=0^{++}$ quantum number. We use two-point QCD sum rule formalism and extract the mass and decay constant values of these states. We take into…