Four-Quark Hadrons: an Updated Review

Abstract

The past decade witnessed a remarkable proliferation of exotic charmonium-like resonances discovered at accelerators. In particular, the recently observed charged states are clearly not interpretable as q-qbar mesons. Notwithstanding the considerable advances on the experimental side, conflicting theoretical descriptions do not seem to provide a definitive picture about the nature of the so-called XYZ particles. We present here a comprehensive review about this intriguing topic, discussing both those experimental and theoretical aspects which we consider relevant to make further progress in the field. At this state of progress, XYZ phenomenology speaks in favour of the existence of compact four-quark particles (tetraquarks) and we believe that realizing this instructs us in the quest for a firm theoretical framework.

120 pages, 53 figures. Several typos corrected and some refs. added in v2

References in corpus (49)

• PYTHIA 6.4 Physics and Manual
• Observation of a resonance-like structure in the pi^+- psi' mass distribution in exclusive B-->K pi^+- psi' decays
• Observation of Two Resonant Structures in e+e- to pi+ pi- psi(2S) via Initial State Radiation at Belle
• Observation of the resonant character of the $Z(4430{)}^{-}$ state
• Measurement of e^+e^- to pi^+pi^-J/psi Cross Section via Initial State Radiation at Belle
• Evidence for a Narrow Near-Threshold Structure in the $J/\psi \varphi$ Mass Spectrum in $B^{+}\to J/\psi \varphi K^{+}$ Decays
• The Z(4430) and a New Paradigm for Spin Interactions in Tetraquarks
• Hadro-Charmonium
• Observation of a near-threshold enhancement in the e+e- -->Lambda_c+Lambda_c- cross section using initial-state radiation
• A Theory of Scalar Mesons
• Pion Interactions in the X(3872)
• Is the X(3872) Production Cross Section at Tevatron Compatible with a Hadron Molecule Interpretation?
• Observation of a new charged charmoniumlike state in B -> J/psi K pi decays
• Search for new charmonium states in the processes e+ e- --> J/psi D(*) D(*) at sqrt{s} ~ 10.6 GeV
• Observation of anomalous Upsilon(1S)pi+pi- and Upsilon(2S)pi+pi- production near the Upsilon(5S) resonance
• Reconciling the X(3872) with the near-threshold enhancement in the D^0\bar{D}^{*0} final state
• A New Picture for the Formation and Decay of the Exotic $XYZ$ Mesons
• Hadronic molecule structure of the Y(3940) and Y(4140)
• Multi-quark hadrons from Heavy Ion Collisions
• Line Shapes of the X(3872)
• Potential model calculations and predictions for heavy quarkonium
• QCD Sum Rules for the X(3872) as a mixed molecule-charmoniun state
• Evidence for diquarks in lattice QCD
• Confirming the molecular nature of the $Z_b(10610)$ and the $Z_b(10650)$
• Heavy quarkonium hybrids from Coulomb gauge QCD
• Where is the χ_{c0}(2P)?
• Implications of heavy quark spin symmetry on heavy meson hadronic molecules
• How Resonances can synchronise with Thresholds
• Are there compact heavy four-quark bound states?
• Charmonium spectroscopy above thresholds
• Low-energy Scattering of $(D{\bar{D}}^{\ast }{)}^{\pm }$ System And the Resonance-like Structure $Z_c(3900)$
• Production of Tetraquarks at the LHC
• Charmed Exotics in Heavy Ion Collisions
• Exotic Heavy Quarkonium Spectroscopy: A Mini-review
• Production of doubly charmed tetraquarks with exotic color configurations in electron-positron collisions
• Estimating the Production Rate of Loosely-bound Hadronic Molecules using Event Generators
• Do $c\bar{c}n\bar{n}$ bound states exist?
• Are There Tetraquarks at Large $N_c$ in QCD(F)?
• Signatures of S-wave bound-state formation in finite volume
• $D_{sJ}$(2317) meson production at RHIC
• Radiative decay of the X(3872) as a mixed molecule-charmonium state in QCD Sum Rules
• Observation of e+e- to K+K-J/psi via Initial State Radiation at Belle
• Line Shapes of the Z(4430)
• Holographic Hadro-Quarkonium
• Adiabaticity and color mixing in tetraquark spectroscopy
• Recent progress on the study of the charmoniumlike states
• Strong Couplings of X(3872)_{J=1,2} and a New Look at J/psi Suppression in Heavy Ion Collisions
• On the Spin of the X(3872)
• Counting valence quarks at RHIC and LHC

Cited by in corpus (43)

• Multiquark Resonances
• Baryons as relativistic three-quark bound states
• Determination of spin and parity of the $Z_c(3900)$
• Employing spin symmetry to disentangle different models for the XYZ states
• Studying the P_c(4450) resonance in J/psi photoproduction off protons
• Hidden charm octet tetraquarks from a diquark-antidiquark model
• XYZ-like Spectra from Laplace Sum Rule at N2LO in the Chiral Limit
• Emergence of molecular-type characteristic spectrum of hidden-charm pentaquark with strangeness embodied in the $P_{\psi s}^{\Lambda }(4338)$ and $P_{cs}(4459)$
• Probing the nature of Z_c states via the eta_c rho decay
• Heavy quark symmetry and weak decays of the $b$-baryons in pentaquarks with a $c\bar{c}$ component
• Spin partners $W_{bJ}$ from the line shapes of the $Z_b(10610)$ and $Z_b(10650)$
• Triply heavy tetraquark states with the $QQ\bar{Q}\bar{q}$ configuration
• How to understand the underlying structures of $X(4140)$, $X(4274)$, $X(4500)$ and $X(4700)$
• Open-flavor charmed/bottom $sq\bar{q}\bar{Q}$ and $qq\bar{q}\bar{Q}$ tetraquark states
• Magnetic and quadrupole moments of the $Z_c(3900)$
• Tetraquark and two-meson states at large $N_{\mathrm{c}}$
• Open charm-bottom scalar tetraquarks and their strong decays
• Production of exotic charmonium in $\gamma \gamma$ interactions at hadronic colliders
• Heavy flavor pentaquarks with four heavy quarks
• Tetraquarks in holographic QCD
• Evidence for a vector charmonium-like state in $e^{+}{e}^{-}\to D_s^{+}{D}_{s2}^{\ast }(2573{)}^{-}+c.c.$
• Magnetic dipole moment of $Z_b(10610)$ in light-cone QCD
• Insights into $Z_b(10610)$ and $Z_b(10650)$ from dipion transitions from ${\rm Y}(10860)$
• Exploring the magnetic dipole moments of $T_{QQ\bar{q}\bar{s}}$ and $T_{QQ\bar{s}\bar{s}}$ states in the framework of QCD light-cone sum rules
• Pair structure of heavy tetraquark systems
• New type of doubly charmed molecular pentaquarks containing most strange quarks: Mass spectra, radiative decays, and magnetic moments
• Weak Decays of Triply Heavy Tetraquarks $b\bar{c}b\bar{q}$
• Constraints from precision measurements on the hadron-molecule interpretation of X,Y,Z resonances
• Hadronic molecules with a $\bar{D}$ meson in a medium
• Charmonium production in ultra-peripheral heavy ion collisions with two-photon processes
• Thermal contribution of unstable states
• Hadronic states with both open charm and bottom in effective field theory
• A note on the newly observed Y(4220) resonance
• Resonance $X(5568)$ as an exotic axial-vector state
• Density of States of a Coupled-Channel System
• Investigating the M1 radiative decay behaviors and the magnetic moments of the predicted triple-charm molecular-type pentaquarks
• Diquark bound states with a completely crossed ladder truncation
• Experimental review of the ${\rm Y}(1S,2S,3S)$ physics at $e^{+}{e}^{-}$ colliders and the LHC
• Electromagnetic properties of the $D{\bar{D}}^{\ast }K$ molecular hexaquark state
• Search for light tetraquark states in ${\rm Y}(1S)$ and ${\rm Y}(2S)$ decays
• The Joint Physics Analysis Center: Recent results
• Some aspects on four quarks recombination
• Mass-Spectroscopy of [$bb][\bar{b}\bar{b}$] and [$bq][\bar{b}\bar{q}$] tetraquark states in a diquark-antidiquark formalism