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Register a new userLong-distance structure of the X(3872)
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We investigate heavy quark symmetries for heavy meson hadronic molecules, and explore the consequences of assuming the X(3872) and $Z_b(10610)$ as an isoscalar $Dbar D^*$ and an isovector $Bbar B^*$ hadronic molecules, respectively. The symmetry allows to predict new hadronic molecules, in particular we find an isoscalar $1^{++}$ $Bbar B^*$ bound state with a mass about 10580 MeV and the isovector charmonium partners of the $Z_b(10610)$ and the $Z_b(10650)$ states. Next, we study the $X(3872) to D^0 bar D^0pi^0$ three body decay. This decay mode is more sensitive to the long-distance structure of the X(3872) resonance than its $J/psipipi$ and $J/psi3pi$ decays, which are mainly controlled by the short distance part of the X(3872) molecular wave function. We discuss the $D^0 bar D^0$ final state interactions, which in some situations become quite important. Indeed in these cases, a precise measurement of this partial decay width could provide precise information on the interaction strength between the $D^{(*)}bar D^{(*)}$ charm mesons.
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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.
Two decades after its unexpected discovery, the properties of the $X(3872)$ exotic resonance are still under intense scrutiny. In particular, there are doubts about its nature as an ensemble of mesons or having any other internal structure. We use a Diffusion Monte Carlo method to solve the many-body Schrodinger equation that describes this state as a $c bar c n bar n$ ($n=u$ or $d$ quark) system. This approach accounts for multi-particle correlations in physical observables avoiding the usual quark-clustering assumed in other theoretical techniques. The most general and accepted pairwise Coulomb$,+,$linear-confining$,+,$hyperfine spin-spin interaction, with parameters obtained by a simultaneous fit of around 100 masses of mesons and baryons, is used. The $X(3872)$ contains light quarks whose masses are given by the mechanism responsible of the dynamical breaking of chiral symmetry. The same mechanisms gives rise to Goldstone-boson exchange interactions between quarks that have been fixed in the last 10-20 years reproducing hadron, hadron-hadron and multiquark phenomenology. It appears that a meson-meson molecular configuration is preferred but, contrary to the usual assumption of $D^0bar{D}^{ast0}$ molecule for the $X(3872)$, our formalism produces $omega J/psi$ and $rho J/psi$ clusters as the most stable ones, which could explain in a natural way all the observed features of the $X(3872)$.
In this paper we consider all possible 1D and 2P ccbar assignments for the recently discovered X(3872). Taking the experimental mass as input, we give numerical results for the E1 radiative widths as well as the three principal types of strong decays; open-charm, ccbar annihilation and closed-charm hadronic transitions. We find that many assignments may be immediately eliminated due to the small observed total width. The remaining viable ccbar assignments are 3D3, 3D2, 1D2, 2 3P1 and 2 1P1. A search for the mode J/psi pi0 pi0 can establish the C-parity of the X(3872), which will eliminate many of these possibilities. Radiative transitions can then be used to test the remaining assignments, as they populate characteristic final states. The 3D2 and 1D2 states are predicted to have large (ca.50%) radiative branching fractions to chi_1 gamma and h_c gamma respectively. We predict that the 3D3 will also be relatively narrow and will have a significant (ca.10%) branching fraction to chi_2 gamma, and should also be observable in B decay. Tests for non-ccbar X(3872) assignments are also discussed.
The recently discovered $X$(3872) has many possible interpretations. We study the production of $X$(3872) with PANDA at GSI for the antiproton-proton collision with two possible interpretations of X(3872). One is as a loosely-bound molecule of $D$-mesons, while another is a 2P charmonium state $chi_{c1}$ (2P). Using effective couplings we are able to give numerical predictions for the production near the threshold and the production associated with $pi^0$. The produced $X$(3872) can be identified with its decay $J/psi pi^+pi^-$. We also study the possible background near the threshold production for $X(3872) to J/psi pi^+pi^-$. With the designed luminosity $1.5{rm fb}^{-1}$ per year of PANDA we find that the event number of $pbar p to J/psi pi^+pi^-$ near the threshold is at the order of $10^6 sim 10^8$, where the large uncertainty comes from the total decay width of X(3872). Our study shows that at the threshold more than about 60% events come from the decay of X(3872) and two interpretations are distinguishable from the line-shape of the production. With our results we except that the PANDA experiments will shed light on the property of X(3872).
Since the discovery of the $X(3872)$ the study of heavy meson molecules has been the subject of many investigations. On the experimental side different experiments have looked for its spin partners and the bottom analogs. On the theoretical side different approaches have been used to understand this state. Some of them are EFT that impose HQSS and so they make predictions for the partners of the $X(3872)$, suggesting the existence of a $J^{PC}=2^{++}$ partner in the charm sector or $J^{PC}=1^{++}$ or $2^{++}$ analogs in the bottom. In our work, in order to understand the $X(3872)$, we use a Chiral quark model in which, due to the proximity to the $DD^*$ threshold, we include $cbar c$ states coupled to $DD^*$ molecular components. In this coupled channel model the relative position of the bare $cbar c$ states with two meson thresholds are very important. We have looked for the $X(3872)$ partners and we dont find a bound state in the $D^*D^*$ $J^{PC}=2^{++}$. In the bottom sector we find the opposite situation where the $B^*B^*$ with $J^{PC}=2^{++}$ is bounded while the $J^{PC}=1^{++}$ is not bounded. These results shows how the coupling with $cbar c$ states can induced different results than those expected by HQSS. The reason is that this symmetry is worse in the open heavy meson sector than in the hidden heavy meson sector.
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