A short review on the compositeness of the $X(3872)$

Abstract

The $X(3872)$ could be a shallow $D{\bar{D}}^{\ast }$ bound state, a compact four-quark state, or a partially composite particle, i.e. a superposition of the two. We will review how these hypotheses could be tested experimentally, examining especially the cases in which the $X$ is a pure bound state or a pure compact tetraquark. Data on $X\to D\bar{D}\pi$ decays are compared with the analysis of the $X$ lineshape. The pure bound state hypothesis corresponds to a well-defined region in parameter space defined by the width of the $D^{\ast }$ versus the binding energy of the $X$. As for the $X$ lineshape, we observe that the currently available experimental analysis tests the compatibility with the compact hypothesis for the $X$. We propose how to extend the analysis to examine the molecular or the partially composite hypotheses. We also review the analysis on the radiative decays of the $X$ including pion corrections confirming some conclusions reached in the literature on the use of the universal wave function description for the molecular $X$.

56 pages, 4 figures. v2: one section added on the the test of compact and molecular hypotheses from the X lineshape. Conclusions unchanged

References in corpus (31)

• Multiquark Resonances
• Observation of the resonant character of the $Z(4430{)}^{-}$ state
• The Z(4430) and a New Paradigm for Spin Interactions in Tetraquarks
• Is the X(3872) Production Cross Section at Tevatron Compatible with a Hadron Molecule Interpretation?
• Reconciling the X(3872) with the near-threshold enhancement in the D^0\bar{D}^{*0} final state
• Study of the lineshape of the ${\chi }_{c1}(3872)$ state
• A Theory of X and Z Multiquark Resonances
• What can radiative decays of the X(3872) teach us about its nature?
• The nature of $X(3872)$ from high-multiplicity $pp$ collisions
• Evidence for X(3872) in PbPb collisions and studies of its prompt production at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV
• Effective range expansion for narrow near-threshold resonances
• Production of Tetraquarks at the LHC
• Remarks on the study of the X(3872) from Effective Field Theory with Pion-Exchange Interaction
• Observation of multiplicity-dependent prompt ${\chi }_{c1}(3872)$ and $\psi (2S)$ production in $pp$ collisions
• From the lineshape of the $X(3872)$ to its structure
• The Hydrogen Bond of QCD in Doubly Heavy Baryons and Tetraquarks
• Galilean-Invariant XEFT
• Towards the quark mass dependence of $T_{cc}^{+}$ from lattice QCD
• One Born$-$Oppenheimer Effective Theory to rule them all: hybrids, tetraquarks, pentaquarks, doubly heavy baryons and quarkonium
• The Hydrogen Bond of QCD
• Doubly Heavy Tetraquarks in the Born-Oppenheimer approximation
• Doubly charm tetraquark channel with isospin $1$ from lattice QCD
• Predicting isovector charmonium-like states from X(3872) properties
• Galilean-Invariant XEFT at Next-to-Leading Order
• Precision Measurement of the Mass of the $D^{\ast 0}$ Meson and the Binding Energy of the $X(3872)$ Meson as a $D^0\overline{D^{\ast 0}}$ Molecule
• The role of the pion in the lineshape of the $X(3872)$
• Constraints from precision measurements on the hadron-molecule interpretation of X,Y,Z resonances
• Probing the nature of the ${\chi }_{c1}(3872)$ state using radiative decays
• Radiative decays $D^*_{(s)}\to D_{(s)}γ$ in covariant confined quark model
• The study on the structure of exotic states ${\chi }_{c1}(3872)$ via beauty-hadron decays in $pp$ collisions at $\sqrt{s}=8\mathrm{TeV}$
• Tetraquarks in the Born-Oppenheimer approximation

Cited by in corpus (3)

• Two nearby states in the $X(3872)$ region: Resolving the radiative-decay ratio tension with ${\eta }_{c2}$
• Exotic hadrons associated with $b$-quark
• The Compact X and Z and their Invisible Molecular Partners