The Belle collaboration recently reported a promising candidate for the spin-2 $D^*\bar{D}^*$ partner of the $X(3872)$, called the $X_2$ for short, having a mass of $(4014.3 \pm 4.0 \pm 1.5)~\mathrm{MeV}$ and a width of $(4 \pm 11 \pm 6)~\mathrm{MeV} $. Assuming the $X_2$ as a pure molecule of the $D^*\bar{D}^*$, we calculated in detail the hidden charmonium decays of the $X_2 \to J/ψV$ and $X_2\toη_cP$ via the intermediate meson loops, where $V = ρ^0\,,ω$ and $P= π^0\,,η\,,η'$. The results indicate that the decay widths are strongly dependent on the $X_2$ mass. At present center value of the mass $4014.3~\mathrm{MeV}$, the width for the $X_2\to J/ψρ^0$ is predicted to be a few tens of keV, while it is on the order of $10^{2\text{-}3}~\mathrm{keV}$ for the $X_2\to J/ ψω$; the predicted width for the $X_2\to η_c π^0$ is about a few keV, while the widths for $X_2\toη_cη$ and $η_cη'$ are around a few tens and tenths of keV, respectively. We also investigated the dependence of the ratios between these widths on the $X_2$ mass and on the $η$-$η'$ mixing angle, which may be good quantities for experiments. We hope that the present calculations would be checked experimentally in the future.
Studying the hidden-charm dipion decays of the charmoniumlike state Y(4360), we show that there exist charged charmoniumlike structures near $D\bar{D}^*$ and $D^*\bar{D}^*$ thresholds in the $J/ψπ^+$, $ψ(2S)π^+$ and $h_c(1P)π^+$ invariant mass spectra of the corresponding hidden-charm dipion decays of Y(4360) using the {\it{Initial Single Pion Emission} mechanism}. We suggest to do further experimental study on these predicted charged enhancement structures, especially by BESIII, Belle, and the forthcoming BelleII.
In this study, the properties of the $J^{PC}=1^{++}$ hidden charm poles are analyzed under the variation of the bare 2P charmonium mass within the effective field theory proposed in Ref.[1]. The main focus of the current work is on the pole trajectory of the $χ_{c1}(2P)$ charmonium dressed by the $D \bar{D}^*$ meson loops. It is shown that the trajectories of the pole change radically for values of the bare charmonium mass above a certain value and also depending on how close the pole is to the threshold.
The observation of $Z_{cs}(3985)$ by BESIII in the $D_s^{*-}D^0$ and $D_s^{-}D^{*0}$ channel adds important dynamic information for a coherent understanding of both $Z_c(3900)$ and $Z_c(4020)$, as well as their strange partners $Z_{cs}(3985)$ and $Z_{cs}(4120)$, on the basis of heavy quark spin symmetry. With an overall short-ranged contact potential in SU(3) flavor symmetry we show that the pole structures can be extracted from the experimental data. Meanwhile, we show the key role played by the $S$-wave open thresholds in $e^+e^-$ annihilations which are correlated with the production of the…
Very recently, the LHCb Collaboration at the Large Hadron Collider at CERN observed new resonance $X(4630)$. The $X(4630)$ is decoded as a charmoniumlike molecule with hidden-strange quantum number well in the one boson exchange mechanism. Especially, the study of its hidden-charmed decays explicitly shows the dominant role of $J/ψϕ$ among all allowed hidden-charmed decays of $X(4630)$, which enforces the conclusion of $X(4630)$ as a charmoniumlike molecule. The discovery of the $X(4630)$ is a crucial step of constructing charmoniumlike molecule zoo.
The BESIII collaboration reported an observation of two charged charmonium-like structure $Z_c^{\pm}(3900)$ and $Z_c^{\pm}(4025)$ in $e^+e^- \to (J/ψπ)^{\pm} π^{\mp}$ and $e^+e^- \to (D^* {\bar D}^*)^{\pm} π^{\mp}$ at ${\sqrt s} =4.26$ GeV recently, which could be an analogue of $Z_b(10610)$ and $Z_b(10650)$ claimed by the Belle Collaboration. In this work, we investigate the hidden-charmonium transitions of $Z_c^{\pm}(3900)$ and $Z_c^{\pm}(4025)$ via intermediate $D^{(*)} {D}^{(*)}$ meson loops. Reasonable results for the branching ratios by taking appropriate values of $α$ in this model can …
Considering the situation that a single chiral partilce, $η$, is initially emitted, we study the hidden-charm di-eta decays of charmoniumlike state $Y(4660)$ and the predicted charmonium $ψ(4790)$, i.e., $Y(4660)/ψ(4790) \to J/ψηη$ through the inetermediates, $η\left[D^{(*)}\bar{D}^{(*)}\right]$ and/or $η \left[D_s^{+(*)}{D}_s^{-(*)}\right]$, and answer to the important question whether there exist isoscalar charmoniumlike structures in the $D^{(*)}\bar{D}^{(*)}$ and/or $D_s^{+(*)}{D}_s^{-(*)}$ channels. Our results predict that there will be enhancement structures near $D\bar{D}^*$, $D^*\bar{…
Decay properties of hidden-strangeness partners of X(3872) are studied in tetra-quark pictures. As the results, it is seen that their decay properties are strongly model dependent, and therefore, experimental studies of them will select a realistic model.
In this article, we study the pseudoscalar bound state $η_c'f_0(980)$ (irrespective of the hadro-charmonium and the molecular state) with the QCD sum rules. Considering the SU(3) symmetry of the light flavor quarks and the heavy quark symmetry, we also study the bound states $η_c'σ(400-1200)$, $η_b'''f_0(980)$ and $η_b'''σ(400-1200)$, and make reasonable predictions for their masses.
We propose the initial single chiral particle emission mechanism, with which the hidden-charm di-kaon decays of higher charmonia and charmonium-like states are studied. Calculating the distributions of differential decay width, we obtain the line shape of the $J/ψK^+$ invariant mass spectrum of $ψ_i\to J/ψK^+K^-$, where $ψ_i=ψ(4415), Y(4660)$, and $ψ(4790)$. Our numerical results show that there exist enhancement structures with both hidden-charm and open-strange decays, which are near the $D\bar{D}_s^*/D^*\bar{D}_s$ and $D^*\bar{D}_s^*/\bar{D}^*{D}_s^*$ thresholds. These charged charmonium-li…
The chiral partner structure of heavy baryons is studied using the bound state approach by binding the heavy-light mesons to nucleon as soliton in an effective Lagrangian for the pseudoscalar and vector mesons based on the hidden local symmetry. In the heavy-light meson sector, we regard the $H$-doublet and $G$-doublet as chiral partners and couple them to light meson with minimal derivative. We find that the chiral partner of $Λ_c(1/2^+,2286)$ is the $Λ_c(1/2^-,3/2^-)$ heavy quark doublet with the mass of about 3.1\,GeV but not ($Λ_c(1/2^-,2595)$, $Λ_c(3/2^-,2625)$) which might be interpreted…
The molecular assignments to the three $P_c$ states and the similar production mechanism between the $Λ_b\to P_c+K$ and $B\to XYZ+K$ convince us the $B$ decaying to a charmonium state plus light mesons could be the appropriate production process to search for the charmoniumlike molecular tetraquarks. In this work, we systematically study the interactions between a charmed (charmed-strange) meson and an anti-charmed (anti-charm-strange) meson, which include the $D^{(*)}\bar{D}^{(*)}$, $\bar{D}^{(*)}\bar{D}_1$, $D^{(*)}\bar{D}_2^*$, $D_s^{(*)}\bar{D}_s^{(*)}$, ${D}_s^{(*)}\bar{D}_{s0}^*$, $D_s^{…
In this work, we predict two charged charmonium-like structures close to the $D^\ast\bar{D}$ and $D^\ast\bar{D}^\ast$ thresholds, where the Initial Single Pion Emission mechanism is introduced in the hidden-charm dipion decays of higher charmonia $ψ(4040)$, $ψ(4160)$, $ψ(4415)$ and charmonium-like state Y(4260). We suggest BESIII to search for these structures in the $J/ψπ^+$, $ψ(2S)π^+$ and $h_b(1P)π^+$ invariant mass spectra of the $ψ(4040)$ decays into $J/ψπ^+π^-$, $ψ(2S)π^+π^-$ and $h_b(1P)π^+π^-$. In addition, the experimental search for these structures in the $J/ψπ^+$, $ψ(2S)π^+$ and $h…
Caution is suggested on the comparison of the spin-singlet charmonium P-state with the centre of gravity of triplet states, when the mass splitting is of the order of a few MeV. The physics of new hidden-charm states X and Y is briefly reviewed. Perspectives for producing double-charm baryons and double-charm exotic mesons are discussed.
In this talk I summarize our recent works on the chiral phase transition in the large flavor QCD studied by the hidden local symmetry (HLS). Bare parameters in the HLS are determined by matching the HLS with the underlying QCD at the matching scale through the Wilsonian matching. This leads to the vector manifestation of the Wigner realization of the chiral symmetry in which the symmetry is restored by the massless degenerate pion (and its flavor partners) and rho meson (and its flavor partners) as the chiral partner.
The isovector partners of the X(3872), recently found at BES III, Belle and CLEO-c were predicted in a simple model based on the chromomagnetic interaction among quarks (H. Hogaasen, J-M. Richard and P. Sorba, Phys. Rev. D73, 054013, 2006). The extension to the hidden-beauty sector is discussed.
The recently observed X(3872) resonance, which is difficult to be assigned a conventional $c\bar{c}$ charmonium state in the quark model, may be interpreted as a molecular state. Such a molecular state is a hidden flavor four quark state because of its charmonium-like quantum numbers. The s-channel one gluon exchange is an interaction which only acts in the hidden flavor multi-quark system. In this paper, we will study the X(3872) and other similiar hidden flavor molecular states in a quark model by taking into account of the s-channel one gluon exchange interaction.
The elaborate analysis of spectrum of charmonium states and charmed hybrids in the mass region over DD-threshold is given. The combined approach based on the potential model and relativistic spherical symmetric top model for decay products has been proposed. The experimental data from different collaborations were analyzed. Especial attention was given to the new states with the hidden charm discovered recently. Eight of these states may be interpreted as higher laying radial excited charmoniumstates. Butmuchmore data on different decay modes are needed for deeper analysis. These data can be d…
We present a model wherein the Higgs mass is protected from the quadratic one-loop top quark corrections by scalar particles that are complete singlets under the Standard Model (SM) gauge group. While bearing some similarity to Folded Supersymmetry, the construction is purely four dimensional and enjoys more parametric freedom, allowing electroweak symmetry breaking to occur easily. The cancelation of the top loop quadratic divergence is ensured by a $Z_3$ symmetry that relates the SM top sector and two hidden top sectors, each charged under its own hidden color group. In addition to the singl…
Assuming that Y(4140) is the second radial excitation of the P-wave charmonium $χ_{cJ}^{\prime\prime}$ ($J=0, 1$), the hidden charm decay mode of Y(4140) is calculated in terms of the rescattering mechanism. Our numerical results show that the upper limit of the branching ratio of the hidden charm decay $Y(4140)\to J/ψϕ$ is on the order of $10^{-4}\sim 10^{-3}$ for both of the charmonium assumptions for Y(4140), which disfavors the large hidden charm decay pattern indicated by the CDF experiment. It seems to reveal that the pure second radial excitation of the P-wave charmonium $χ_{cJ}^{\prime…
We investigate the processes $e^+e^-$$\to$$γJ/ψϕ$, $γJ/ψω$ and $π^0 J/ψη$ to search for the charmnium-like states with hidden $s\bar{s}$, such as $Y(4140)$, $Y(4274)$, $X(4350)$ and $X(3915)$. These processes will receive contributions from the charmed-strange meson rescatterings. When the center-of-mass energies of the $e^+e^-$ scatterings are taken around the $D_{s0}(2317)D_s^{*}$, $D_{s1}(2460)D_s$ or $D_{s1}(2460)D_s^{*}$ threshold, the anomalous triangle singularities can be present in the rescattering amplitudes, which implies a non-resonance explanation about the resonance-like structur…
Recently BESIII collaboration discovered a charged strange hidden-charm state $Z_{cs}$(3985) in the $D_s^-D^{*0} + D_s^{*-}D^{0}$ spectrum. A higher $Z'_{cs}$ state coupling to $\bar{D}_s^{*-}D^{*0}$ is expected by SU(3)-flavor symmetry, and their bottom partners are anticipated by heavy quark flavor symmetry. Here we study the photoproduction of these exotic states and investigate carefully the background from Pomeron exchange. Our results indicate that the maximal photoproduction cross section of strange partner is around 1 $\sim$ 2 orders of magnitude smaller than that of the corresponding …
We calculate the decay widths of the charmonium states, $J/ψ$, $ψ(3686)$ and $ψ(3770)$, to $D\bar D$ pairs, as well as the decay width of $D^* \rightarrow Dπ$, in isospin asymmetric strange hadronic matter, using a field theoretical model for composite hadrons with quark constituents. For this purpose we use the quark antiquark pair creation term of the free Dirac Hamiltonian written in terms of the constituent quark field operators, and use explicit charmonium, $D$, $\bar {D}$, $D^*$ and $π$ states to evaluate the matrix elements for the charmonium as well as $D^*$ decay amplitudes. The mediu…
In the framework of the color-magnetic interaction, we have systematically studied the mass splittings of the possible hidden-charm pentaquarks $qqqc\bar{c}$ ($q=u,d,s$) where the three light quarks are in a color-octet state. We find that i) the LHCb $P_c$ states fall in the mass region of the studied system; ii) most pentaquarks should be broad states since their $S$-wave open-charm decays are allowed while the lowest state is the $J^P=\frac12^-$ $Λ$-like pentaquark with probably the suppressed $η_cΛ$ decay mode only; and iii) the $J^P=\frac52^-$ states do not decay through $S$-wave and thei…
We have studied the loosely bound $D^*\bar{D}^*$ system. Our results indicate that the recently observed charged charmonium-like structure $Z_c(4025)$ can be an ideal $D^*\bar{D}^*$ molecular state. We have also investigated its pionic, dipionic, and radiative decays. We stress that both the scalar isovector molecular partner $Z_{c0}$ and three isoscalar partners ${\tilde Z}_{c0,c1,c2}$ should also exist if $Z_c(4025)$ is a $D^*\bar{D}^*$ molecular state {in the framework of the one-pion-exchange model}. $Z_{c0}$ can be searched for in the channel $e^+e^-\to Y \to Z_{c0}(4025)\left(ππ\right)_{…
Strong decays of the charmonium-like state $Y(4320)$ have been studied in the framework of the covariant confined quark model. The resonance $Y$ has been interpreted as a four-quark state of the molecular type. We evaluate the hidden-charm decay width of $Y$ to a vector and a scalar, with the latter decaying subsequently to a pair of charged pseudoscalar states. The strong decay modes $Y \!\to\! π^{+}π^{-}J/Ψ$ and $Y \!\to\! K^{+}K^{-} J/Ψ$ have been studied by involving the scalar resonance state $f_0(980)$. We have calculated the fractal widths of the related strong decays and the branching …
Motivated by the very recent discovery of the strange hidden-charm exotic state $Z_{cs}(3985)$ by the BESIII Collaboration, we study possible interpretation of this exotic state both at $ T= 0 $ and $ T\neq 0 $. We analytically compute the mass and meson-current coupling constant of this resonance with spin-parity $ J^{PC} = 1^{+-}$ at finite temperature approximation up to sixth order of the thermal operator dimension including non-perturbative contributions. Extracting thermal mass and meson-current coupling constant sum rules, the modifications on properties of $Z_{cs}(3985)$ state in hot m…
This work uses the QCD Sum Rules to study the masses of the $D_s \bar{D}_s^*$ and $D_s^* \bar{D}_s^*$ molecular states with quantum numbers $J^{PC} = 1^{+-}$. Interpolating currents with definite C-parity are employed, and the contributions up to dimension eight in the Operator Product Expansion (OPE) are taken into account. The results indicate that two hidden strange charmonium-like states may exist in the energy ranges of $3.83 \sim 4.13 $ GeV and $4.22 \sim 4.54 $ GeV, respectively. The hidden strange charmonium-like states predicted in this work may be accessible in future experiments, e.…
The charmonium dissociation by mesons in relativistic heavy-ion reactions is analyzed within the Regge approach. It is shown that the inclusion of the initial and final state interactions in the dissociation of J/Psi to bar{D}* D* close to threshold increases the cross section significantly and can not be neglected in comparison to the total dissociation rate. This is due to resonant bar{D}*-D* interactions in sqrt{s} close to the masses of the Psi(4.04) and Psi(4.16) mesons. We also investigate thermal effects of the (c bar{c}) width for such processes in the medium. All these effects change …
We study baryo-charmonium [$η_{\rm c}$- and $J/ψ$-$N^*$, $η_{\rm c}(2S)$-, $ψ(2S)$- and $χ_{\rm c}(1P)$-$N$] and baryo-bottomonium [$η_{\rm b}(2S)$-, $Υ(2S)$- and $χ_{\rm b}(1P)$-$N$] bound states, where $N$ is the nucleon and $N^*$ a nucleon resonance. In the baryo-quarkonium model, the five $qqq Q \bar Q$ quarks are arranged in terms of a heavy quarkonium core, $Q \bar Q$, embedded in light baryonic matter, $qqq$, with $q = u$ or $d$. The interaction between the $Q \bar Q$ core and the light baryon can be written in terms of the QCD multipole expansion. The spectrum of baryo-charmonium state…
I classify exotic hadrons into two types, "genuine" and "hidden" exotics, and propose that the "hidden" exotics would be interpreted as "chiralons" in the ~U(12)_SF times O(3,1)_L-classification scheme of hadrons. Based upon this conjecture I investigate the mass spectrum of 1S, 1P, and 2S states for the ccbar system by use of a phenomenological mass formula with the spin-dependent interactions and present possible assignments for exotic neutral charmonium-like states which were recently discovered. It is also mentioned that some J^PC-exotic states predicted in this scheme might correspond to …
With the spin rearrangement, we have performed a comprehensive investigation of the decay patterns of the S-wave tetraquarks and P-wave tetraquarks where the P-wave excitation exists either between the diquark and anti-diquark pair or inside the diquark. Especially, we compare the decay patterns of $Y(4260)$ with different inner structures such as the conventional charmonium, the molecule, the P-wave tetraquark and the hybrid charmonium. We notice the $J/ψππ$ mode is suppressed in the heavy quark symmetry limit if $Y(4260)$ is a molecular state. Moreover the hybrid charmonium and hidden-charm …
Stimulated by the new evidence of Y(4274) observed in the $J/ψϕ$ invariant mass spectrum, we first propose the charmonium-like state Y(4274) as the S-wave $D_s\bar{D}_{s0}(2317)+h.c.$ molecular state with $J^P=0^-$, which is supported well by dynamics study of the system composed of the pseudoscalar and scalar charmed mesons. The S-wave $D\bar{D}_{0}(2400)+h.c.$ molecular charmonium appears as the molecular partner of Y(4274), which is in accord with the enhancement structure appearing at 4.2 GeV in the $J/ψω$ invariant mass spectrum from B decays. Our study shows that the enhancement structur…
In this paper we develop a formalism for incorporating hadron loops in the quark model. We derive expressions for mass shifts, continuum components and mixing amplitudes of "quenched" quark model states due to hadron loops, as perturbation series in the valence-continuum coupling Hamiltonian. We prove three general theorems regarding the effects of hadron loops, which show that given certain constraints on the external "bare" quark model states, the valence-continuum coupling, and the hadrons summed in the loops, the following results hold: (1) The loop mass shifts are identical for all states…
We study a scenario that a hidden gaugino dark matter decays into the standard-model particles (and their supersymmetric partners) through a kinetic mixing with the gaugino of a U(1)B-L broken at a scale close to the grand unification scale. We show that decay of the hidden gaugino can explain excesses in the cosmic-ray electrons and positrons observed by PAMELA and Fermi.
In this article, we assume that there exist hidden charmed tetraquark states with the spin-parity $J^P=1^-$, and calculate their masses with the QCD sum rules. The numerical result indicates that the masses of the vector hidden charmed tetraquark states are about $M_{Z}=(5.12\pm0.15) \rm{GeV}$ or $M_{Z}=(5.16\pm0.16) \rm{GeV}$, which are inconsistent with the experimental data on the $π^+ χ_{c1}$ invariant mass distribution. The hidden charmed mesons $Z_1$, $Z_2$ or $Z$ may be scalar hidden charmed tetraquark states, hadro-charmonium resonances or molecular states.
The pentaquark $P_c^+(4450)$ recently discovered by LHCb has been interpreted as a bound state of $Ψ(2S)$ and nucleon. The charmonium-nucleon interaction which provides the binding mechanism is given, in the heavy quark limit, in terms of charmonium chromoelectric polarizabilities and densities of the nucleon energy-momentum tensor (EMT). In this work we show in model-independent way, by exploring general properties of the effective interaction, that $Ψ(2S)$ can form bound states with nucleon and $Δ$. Using the Skyrme model to evaluate the effective interaction in the large-$N_c$ limit and est…
The possibility of the Y(4260) being the molecular state of $D\bar D_1(2420)+\mathrm{c.c.}$ is investigated in the one boson exchange model. It turns out that the potential of $J^{PC}=1^{--}$ state formed by $D\bar D_1(2420)+\mathrm{c.c.}$ is attractive and strong enough to bind them together when the momentum cutoff $Λ\gtrsim 1.4$ GeV. To produce the Y(4260) with correct binding energy, we need $Λ\approx 2.1$ GeV. Besides, $D\bar D_1(2420)+\mathrm{c.c.}$ can also form a state with exotic quantum numbers, $J^{PC}=1^{-+}$, and its potential similar with that of the $J^{PC}=1^{--}$ state. Theref…
Production of Drell-Yan pairs and open and hidden heavy flavor on nuclear targets is examined within perturbative QCD. The effects of modifications of nucleon structure functions inside the nuclear medium are considered. Besides, nuclear dependence of charmonium and bottonium absorption is studied in the framework of the Glauber-Gribov model. The low energy limit of this approach recovers the probabilistic formula usually employed for charmonium and bottonium suppression in nuclear collisions.
By investigating the very closely lied $D_{s1}\bar{D}_{s}+c.c.$ and $D_{s0}\bar{D}^*_{s}+c.c.$ thresholds at about 4.43 GeV we propose that the $ψ(4415)$ and $ψ(4160)$ can be mixing states between the dynamic generated states of the strong $S$-wave $D_{s1}\bar{D}_{s}+c.c.$ and $D_{s0}\bar{D}^*_{s}+c.c.$ interactions and the quark model states $ψ(4S)$ and $ψ(2D)$. We investigate the $J/ψK\bar{K}$ final states and invariant mass spectrum of $J/ψK$ to demonstrate that nontrivial lineshapes can arise from such a mechanism. This process, which goes through triangle loop transitions, is located in t…
The hidden charm pentaquark state $P_c(4450)$ observed recently by the LHCb collaboration may be of molecular nature, as advocated by some unitary approaches that also predict pentaquark partners in the strangeness $S=-1$ sector. In this work we argue that a hidden-charm strange pentaquark could be seen from the decay of the $Λ_b$, just as in the case of the non-strange $P_c(4450)$, but looking into the $J/ψηΛ$ decay mode and forming the invariant mass spectrum of $J/ψΛ$ pairs. In the model presented here, which assumes a standard weak decay topology and incorporates the hadronization process …
In the framework of one-pion-exchange (OPE) model, we study the hidden-charm and charm-strange molecular pentaquark systems composed of a heavy baryon $(Σ_c, Σ_c^*)$ and a vector meson $(\bar{K}^*, \bar{D}^*)$, where the S-D mixing effect is considered in our calculation. Our result shows that the $Σ_c\bar{D}^*$ molecular state with $(I=1/2,J^P=3/2^-)$ and the $Σ_c^*\bar{D}^*$ molecular state with $(I=1/2,J^P=5/2^-)$ exist in the mass range of the observed $P_c(4380)$ and $P_c(4450)$, respectively. Moreover, we predict two other hidden-charm molecular pentaquarks with configurations $Σ_c\bar{D…
Since 2003 many charmonium-like states were observed experimentally. Especially those charged charmonium-like $Z_c$ states and bottomonium-like $Z_b$ states cannot be accommodated within the naive quark model, which are good candidates of either the hidden-charm tetraquark states or molecules composed of a pair of charmed mesons. In 2015, the LHCb Collaboration discovered two hidden-charm pentaquark states, which are also beyond the quark model. In this talk, we review the current experimental progress and investigate various theoretical interpretations of these candidates of the multiquark st…
We study the mass spectra for the $cc\bar c\bar c$ and $bb\bar b\bar b$ tetraquark states by developing a moment sum rule method. Our results show that the $bb\bar b\bar b$ tetraquarks lie below the threshold of $η_b(1S)η_b(1S)$. They are probably stable and very narrow. The masses for the doubly hidden-charm states $cc\bar c\bar c$ are higher than the spontaneous dissociation thresholds of two charmonium mesons. We suggest to search for such states in the $J/ψJ/ψ$ and $η_c(1S)η_c(1S)$ channels.
We identify the recently observed charmonium-like structure $Z_c^\pm(3900)$ as the charged partner of the X(3872) state. Using standard techniques of QCD sum rules, we evaluate the three-point function and extract the coupling constants of the $Z_c \, J/ψ\, π^+$ and $Z_c \, η_c \, ρ^+$ vertices and the corresponding decay widths in these channels. The good agreement with the experimental data gives support to the tetraquark picture of this state.
By using QCD sum rules, the mass of the hidden charm tetraquark $[cu][\bar{c}\bar{d}]$ state with $I^{G} (J^{P}) = 1^+ (1^{+})$ (HCTV) is estimated, which presumably will turn out to be the newly observed charmonium-like resonance $Z_c^+(3900)$. In the calculation, contributions up to dimension eight in the operator product expansion(OPE) are taken into account. We find $m_{1^+}^c = (3912^{+306}_{-153}) \, \text{MeV}$, which is consistent, within the errors, with the experimental observation of $Z_c^+(3900)$. Extending to the b-quark sector, $m_{1^+}^b = (10561^{+395}_{-163}) \,\text{MeV}$ is …
Decays of X(3872) and its partners as hidden-charm axial-vector tetra-quark mesons are studied. As the result, it is seen that the iso-triplet partners of X(3872) can be broad, and therefore, higher statistics would be needed to find them.
In the past decade many charmonium-like states were observed experimentally. Especially those charged charmonium-like $Z_c$ states and bottomonium-like $Z_b$ states can not be accommodated within the naive quark model. These charged $Z_c$ states are good candidates of either the hidden-charm tetraquark states or molecules composed of a pair of charmed mesons. Recently, the LHCb Collaboration discovered two hidden-charm pentaquark states, which are also beyond the quark model. In this work, we review the current experimental progress and investigate various theoretical interpretations of these …
Using a constituent quark model we study the mass and decay channels of meson meson and meson baryon structures in the charm sector. We show that the $X(3872)$ and $X(3940)$ resonances can be described as mixed charmonium-molecular states with $J^{PC}=1^{++}$, whereas the $X(3915)$ and the $Y(3940)$ can be assigned to similar mixed states with $J^{PC}=0^{++}$. In the baryon spectrum we identify the $Λ^+_c(2940)$ as a $D^*N$ molecule with $(I)J^P=(0)3/2^-$ and the recently reported $X_c(3250)$ as a $D^*Δ$ resonance with $(I)J^P=(1)5/2^-$ or $(I)J^P=(2)3/2^-$.
We study the near-threshold $J/ψ$ meson photoproduction from protons and nuclei by considering incoherent direct non-resonant ($γp \to {J/ψ}p$, $γn \to {J/ψ}n$) and two-step resonant ($γp \to P_{ci}^+ \to {J/ψ}p$, $γn \to P_{ci}^0 \to {J/ψ}n$, $i=1$, 2, 3, 4; $P_{c1}^{+,0}=P_c^{+,0}(4312)$, $P_{c2}^{+,0}=P_c^{+,0}(4337)$, $P_{c3}^{+,0}=P_c^{+,0}(4440)$, $P_{c4}^{+,0}=P_c^{+,0}(4457)$) charmonium production processes. We calculate the absolute excitation functions, energy and momentum distributions for the non-resonant, resonant and for the combined (non-resonant plus resonant) production of $J…
The charmoniumlike state $Y(4260)$ is described as predominantly a $D_1 \bar{D}$ molecule in a coupled-channel quark model [Phys.\,Rev.\,D\,\textbf{96},\,114022\,(2017)]. The heavy quark spin symmetry (HQSS) thus implies the possible emergence of its heavy quark spin partners with molecular configuration as $D_1 \bar{D}^*$ and $D_2^* \bar{D}^*$ below these charmed mesons' thresholds. We analyze the probabilities of various intermediate charmed meson loops for $J^{PC}=1^{--}$ exotic state $Y(4360)$ and find that the channel $D_1 \bar{D}^*$ couples more strongly around its mass regime, and the c…
In a previous paper we suggested an explanation for the peak designated as $Z(4430)^+$ in the $ψ^\primeπ^+$ mass spectrum, observed by Belle in ${\bar{\!B}} \to {ψ^\prime} π^+ K$ decays, as an effect of $\bar{\!D}{}^{\,*0}D^{\,+} \to ψ^\primeπ^+$ rescattering in the decays ${\bar{\!B}} \to {D_{s}^{\,\prime -}} {D}$, where the $D_{s}^{\,\prime -}$ is an as-yet unobserved radial excitation of the pseudoscalar ground state $D_{s}^{\,-}$-meson. In this paper, we demonstrate that this hypothesis provides an explanation of the double $Z^+$-like peaking structures, which were studied by LHCb with muc…
Starting from a molecular picture for the X(3872) resonance, this state and its J^{PC}=2++ HQSS partner [X2(4012)] are analyzed within a model which incorporates possible mixings with 2P charmonium states. Since it is reasonable to expect the bare chi_{c1}(2P) to be located above the D\bar D* threshold, but relatively close to it, the presence of the charmonium state provides an effective attraction that will contribute to bind the X(3872), but it will not appear in the 2++ sector. Indeed in this latter sector, the chi_{c2}(2P) should provide an effective small repulsion, because it is placed …
We first present a non-resonant description to charmonium-like structure $Y(4360)$ in the $ψ(2S)π^+π^-$ invariant mass spectrum of the $e^+e^-\to ψ(2S)π^+π^-$ process. The $Y(4360)$ structure is depicted well by the interference effect of the production amplitudes of $e^{+} e^{-} \to ψ(2S) π^+ π^-$ via the intermediate charmonia $ψ(4160)/ψ(4415)$ and direct $e^+e^-$ annihilation into $ψ(2S)π^+ π^-$. This fact shows that $Y(4360)$ is not a genuine resonance, which naturally explains why $Y(4360)$ was only reported in its hidden-charm decay channel $ψ(2S)π^+π^-$ and was not observed in the exclu…
Heavy-light diquarks can be the building blocks of a rich spectrum of states which can accommodate some of the newly observed charmonium-like resonances not fitting a pure c-cbar assignment. We examine this possibility for hidden and open charm diquark-antidiquark states deducing spectra from constituent quark masses and spin-spin interactions. Taking the X(3872) as input we predict the existence of a 2++ state that can be associated to the X(3940) observed by Belle and re-examine the state claimed by SELEX, X(2632). The possible assignment of the previously discovered states D_s(2317) and D_s…
Some of the non-relativistic QQ/bar interaction potentials and its isospectral partner-potentials have been employed to evaluate the masses and leptonic decay widths of Charmonium and Upsilon states. An attempt has been made to develop a prescription to provide a simultaneous fit to Masses and leptonic decay widths of Quarkonia. Preliminary calculation shows that the class of isospectral-potentials corresponding to: V(r)= -(alphas/r)+ar^n appears to yield the desired results. The various associated theoretical and phenomenological issues are discussed in light of recent data. The possible rela…
