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We investigate heavy quark symmetries for heavy light meson-antimeson systems in a contact-range effective field theory. In the SU(3) light flavor limit, the leading order Lagrangian respecting heavy quark spin symmetry contains four independent counter-terms. Neglecting $1/m_Q$ corrections, three of these low energy constants can be determ1ined by theorizing a molecular description of the $X(3872)$ and $Z_b(10610)$ states. Thus, we can predict new hadronic molecules, in particular the isovector charmonium partners of the $Z_b(10610)$ and the $Z_b(10650)$ states. We also discuss hadron molecules composed of a heavy meson and a doubly-heavy baryon, which would be related to the heavy meson-antimeson molecules thanks to the heavy antiquark-diquark symmetry. Finally, we also study the $X(3872) to D^0bar D^0pi^0$ decay, which is not only sensitive to the short distance part of the $X(3872)$ molecular wave function, as the $J/psipipi$ and $J/psi3pi$ $X(3872)$ decay modes are, but it is also affected by the long-distance structure of the resonance. Furthermore, this decay might provide some information on the interaction between the $Dbar D$ charm mesons.
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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 non-strange states. The possibility of searching for them in future electron-ion colliders (EIC) is briefly discussed.
In this work, we study possible hidden-bottom molecular pentaquarks $P_b$ from coupled-channel $Sigma^{(*)}_bB^{(*)}-Lambda_bB^{(*)}$ interaction in the quasipotential Bethe-Salpeter equation approach. In isodoublet sector with $I=1/2$, with the same reasonable parameters the interaction produces seven molecular states, a state near $ Sigma_bB$ threshold with spin parity $J^P=1/2^-$, a state near $Sigma^*_bB$ threshold with $3/2^-$, two states near $Sigma_bB^*$ threshold with $1/2^-$ and $3/2^-$, and three states near $Sigma_b^*B^*$ threshold with $1/2^-$, $3/2^-$, and $5/2^-$. The results suggest that three states near $Sigma_b^* B^*$ threshold and two states near $Sigma_b B^*$ threshold are very close, respectively, which may be difficult to distinguish in experiment without partial wave analysis. Compared with the hidden-charm pentaquark, the $P_b$ states are relatively narrow with widths at an order of magnitude of 1 MeV or smaller. The importance of each channel considered is also discussed, and it is found that the $Lambda_b B^*$ channel provides important contribution for the widths of those states. In isoquartet sector with $I=3/2$, cutoff should be considerably enlarged to achieve bound states from the interaction, which makes the existence of such states unreliable. The results in the current work are helpful for searching for hidden-bottom molecular pentaquarks in future experiments, such as the COMPASS, J-PARC, and the Electron Ion Collider in China (EicC).
Recently, the LHCb Collaboration reported three $P_c$ states in the ${J/psi}p$ channel. We systematically study the mass spectrum of the hidden charm pentaquark in the framework of an extended chromomagnetic model. For the $nnncbar{c}$ pentaquark with $I=1/2$, we find that (i) the lowest state is $P_{c}(4327.0,1/2,1/2^{-})$ [We use $P_{c}(m,I,J^{P})$ to denote the $nnncbar{c}$ pentaquark], which corresponds to the $P_{c}(4312)$. Its dominant decay mode is $Lambda_{c}bar{D}^{*}$. (ii) We find two states in the vicinity of $P_{c}(4380)$. The first one is $P_{c}(4367.4,1/2,3/2^{-})$ and decays dominantly to $N{J/psi}$ and $Lambda_{c}bar{D}^{*}$. The other one is $P_{c}(4372.4,1/2,1/2^{-})$. Its dominant decay mode is $Lambda_{c}bar{D}$, and its partial decay width of $Neta_{c}$ channel is comparable to that of $N{J/psi}$. (iii) In higher mass region, we find $P_{c}(4476.3,1/2,3/2^{-})$ and $P_{c}(4480.9,1/2,1/2^{-})$, which correspond to $P_{c}(4440)$ and $P_{c}(4457)$. In the open charm channels, both of them decay dominantly to the $Lambda_{c}bar{D}^{*}$. (iv) We predict two states above $4.5~text{GeV}$, namely $P_{c}(4524.5,1/2,3/2^{-})$ and $P_{c}(4546.0,1/2,5/2^{-})$. The masses of the $nnncbar{c}$ state with $I=3/2$ are all over $4.6~text{GeV}$. Moreover, we use the model to explore the $nnscbar{c}$, $ssncbar{c}$ and $ssscbar{c}$ pentaquark states.
We analyze the decay modes of the three $[frac 12frac 12^-]_{S=0,1}$ and $[frac 12frac 32^-]_{S=1}$ non-strange pentaquarks with hidden charm and bottom, predicted by holographic QCD in the heavy quark limit. In leading order, the pentaquarks %are composed of heavy-light mesons in bulk bound to an instanton core. They are degenerate and stable by heavy quark symmetry. At next to leading order, the spin interactions lift the degeneracy and cause the pentaquarks to decay. We show that the open charm (bottom) decay modes dwarf the hidden charm (bottom) ones, with total widths that are consistent with those recently reported by LHCb for charm pentaquarks. Predictions for bottom pentaquarks are given.
The lightest hidden-bottom tetraquarks in the dynamical diquark model fill an $S$-wave multiplet consisting of 12 isomultiplets. We predict their masses and dominant bottomonium decay channels using a simple 3-parameter Hamiltonian that captures the core fine-structure features of the model, including isospin dependence. The only experimental inputs needed are the corresponding observables for $Z_b(10610)$ and $Z_b(10650)$. The mass of $X_b$, the bottom analogue to $X(3872)$, is highly constrained in this scheme. In addition, using lattice-calculated potentials we predict the location of the center of mass of the $P$-wave multiplet and find that $Y(10860)$ fits well but the newly discovered $Y(10750)$ does not, more plausibly being a $D$-wave bottomonium state. Using similar methods, we also examine the lowest $S$-wave multiplet of 6 $cbar c sbar s$ states, assuming as in earlier work that $X(3915)$ and $Y(4140)$ are members, and predict the masses and dominant charmonium decay modes of the other states. We again use lattice potentials to compute the centers of mass of higher multiplets, and find them to be compatible with the masses of $Y(4626)$ ($1P$) and $X(4700)$ ($2S$), respectively.
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