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Register a new userIs $X(7200)$ the heavy anti-quark diquark symmetry partner of $ X(3872)$?
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The $D^{(ast)}Xi_{cc}^{(ast)}$ system and $bar{Xi}_{cc}^{(ast)}Xi_{cc}^{(ast)}$ system can be related to the $D^{(ast)}bar{D}^{(ast)}$ system via heavy anti-quark di-quark symmetry (HADS). In this work, we employ a contact-range effective field theory to systematically investigate the likely existence of molecules in these systems in terms of the hypothesis that X(3872) is a $1^{++}$~$Dbar{D}^{ast}$ bound state in the isospin symmetry limit, with some of the unknown low energy constants estimated using the light-meson saturation approximation. In the meson-meson system, a $J^{PC}=2^{++}$~$bar{D}^{ast}D^{ast}$ molecule commonly referred to as $X(4013)$ is reproduced, which is the heavy quark spin partner of $X(3872)$. In the meson-baryon system, we predict two triply charmed pentaquark molecules, $J^{P}=1/2^{-}$~$D^{ast}Xi_{cc}$ and $J^{P}=5/2^{-}$~$D^{ast}Xi_{cc}^{ast}$. In the baryon-baryon system, there exist seven di-baryon molecules, $J^{PC}=0^{-+}$~$bar{Xi}_{cc}Xi_{cc}$, $J^{PC}=1^{--}$~$bar{Xi}_{cc}Xi_{cc}$, $J^{PC}=1^{-+}$~$bar{Xi}_{cc}Xi_{cc}^{ast}$, $J^{PC}=1^{--}$~$bar{Xi}_{cc}Xi_{cc}^{ast}$, $J^{PC}=2^{-+}$~$bar{Xi}_{cc}Xi_{cc}^{ast}$, $J^{PC}=2^{-+}$~$bar{Xi}_{cc}^{ast}Xi_{cc}^{ast}$ and $J^{PC}=3^{--}$~$bar{Xi}_{cc}^{ast}Xi_{cc}^{ast}$. Among them, the $J^{PC}=0^{-+}$~$bar{Xi}_{cc}Xi_{cc}$ and/or $J^{PC}=1^{--}$~$bar{Xi}_{cc}Xi_{cc}$ molecules may contribute to the $X(7200)$ state recently observed by the LHCb Collaboration, which implies that $X(7200)$ can be related to $X(3872)$ via HADS. As a byproduct, with the heavy quark flavor symmetry we also study likely existence of molecular states in the $B^{(ast)}bar{B}^{(ast)}$, $bar{B}^{(ast)}Xi_{bb}^{(ast)}$, and $bar{Xi}_{bb}^{(ast)}Xi_{bb}^{(ast)}$ systems.
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In this work, an Effective Field Theory (EFT) incorporating light SU(3)-flavour and heavy quark spin symmetry is used to describe charmed meson-antimeson bound states. At Lowest Order (LO), this means that only contact range interactions among the heavy meson and antimeson fields are involved. Besides, the isospin violating decays of the X(3872) will be used to constrain the interaction between the $D$ and a $bar{D}^*$ mesons in the isovector channel. Finally, assuming that the X(3915) and Y(4140) resonances are $D^*bar{D}^*$ and $D_s^*bar{D}_s^*$ molecular states, we can determine the four Low Energy Constants (LECs) of the EFT that appear at LO and, therefore, the full spectrum of molecular states with isospin I=0, 1/2 and 1.
It has been proposed recently (Phys. Rev. Lett. 115 (2015), 022001) that the charmoniumlike state named X(3915) and suggested to be a $0^{++}$ scalar, is just the helicity-0 realisation of the $2^{++}$ tensor state $chi_{c2}(3930)$. This scenario would call for a helicity-0 dominance, which were at odds with the properties of a conventional tensor charmonium, but might be compatible with some exotic structure of the $chi_{c2}(3930)$. In this paper, we investigate, if such a scenario is compatible with the assumption that the $chi_{c2}(3930)$ is a $D^*bar D^*$ molecular state - a spin partner of the $X(3872)$ treated as a shallow bound state. We demonstrate that for a tensor molecule the helicity-0 component vanishes for vanishing binding energy and accordingly for a shallow bound state a helicity-2 dominance would be natural. However, for the $chi_{c2}(3930)$, residing about 100 MeV below the $D^*bar D^*$ threshold, there is no a priori reason for a helicity-2 dominance and thus the proposal formulated in the above mentioned reference might indeed point at a molecular structure of the tensor state. Nevertheless, we find that the experimental data currently available favour a dominant contribution of the helicity-2 amplitude also in this scenario, if spin symmetry arguments are employed to relate properties of the molecular state to those of the X(3872). We also discuss what research is necessary to further constrain the analysis.
In this letter, we propose interpolating currents for the X(3872) resonance, and show that, in the Heavy Quark limit of QCD, the X(3872) state should have degenerate partners, independent of its internal structure. Magnitudes of possible I=0 and I=1 components of the X(3872) are also discussed.
Heavy ion collisions provide a unique opportunity to study the nature of X(3872) compared with electron-positron and proton-proton (antiproton) collisions. With the abundant charm pairs produced in heavy-ion collisions, the production of multicharm hadrons and molecules can be enhanced by the combination of charm and anticharm quarks in the medium. We investigate the centrality and momentum dependence of X(3872) in heavy-ion collisions via the Langevin equation and instant coalescence model (LICM). When X(3872) is treated as a compact tetraquark state, the tetraquarks are produced via the coalescence of heavy and light quarks near the quantum chromodynamic (QCD) phase transition due to the restoration of the heavy quark potential at $Trightarrow T_c$. In the molecular scenario, loosely bound X(3872) is produced via the coalescence of $D^0$-$bar D^{*0}$ mesons in a hadronic medium after kinetic freeze-out. The phase space distributions of the charm quarks and D mesons in a bulk medium are studied with the Langevin equation, while the coalescence probability between constituent particles is controlled by the Wigner function, which encodes the internal structure of the formed particle. First, we employ the LICM to explain both $D^0$ and $J/psi$ production as a benchmark. Then, we give predictions regarding X(3872) production. We find that the total yield of tetraquark is several times larger than the molecular production in Pb-Pb collisions. Although the geometric size of the molecule is huge, the coalescence probability is small due to strict constraints on the relative momentum between $D^0$ and $bar D^{*0}$ in the molecular Wigner function, which significantly suppresses the molecular yield.
It was recently proposed that the $X(3872)$ binding energy, the difference between the $D^0bar D^{*0}$ threshold and the $X(3872)$ mass, can be precisely determined by measuring the $gamma X(3872)$ line shape from a short-distance $D^{*0}bar D^{*0}$ source produced at high-energy experiments. Here, we investigate the feasibility of such a proposal by estimating the cross sections for the $e^+e^-topi^0gamma X(3872)$ and $pbar ptogamma X(3872)$ processes considering the $D^{*0}bar D^{*0}D^0/bar D^{*0}D^{*0}bar D^0$ triangle loops. These loops can produce a triangle singularity slightly above the $D^{*0}bar D^{*0}$ threshold. It is found that the peak structures originating from the $D^{*0}bar D^{*0}$ threshold cusp and the triangle singularity are not altered much by the energy dependence introduced by the $e^+e^-topi^0D^{*0}bar D^{*0}$ and $pbar ptobar D^{*0}D^{*0}$ production parts or by considering a finite width for the $X(3872)$. We find that $sigma(e^+e^-topi^0gamma X(3872)) times {rm Br}(X(3872)topi^+pi^-J/psi)$ is $mathcal{O}(0.1~{rm fb})$ with the $gamma X(3872)$ invariant mass integrated from 4.01 to 4.02 GeV and the c.m. energy of the $e^+e^-$ pair fixed at 4.23 GeV. The cross section $sigma(pbar ptogamma X(3872))times {rm Br}(X(3872)topi^+pi^-J/psi)$ is estimated to be of $mathcal{O}(10~{rm pb})$. Our results suggest that a precise measurement of the $X(3872)$ binding energy can be done at PANDA.
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