QCD Sum Rules Approach to the $X,Y$ and $Z$ States

Abstract

In the past decade, due to the experimental observation of many charmonium-like states, there has been a revival of hadron spectroscopy. In particular, the experimental observation of charged charmonium-like, $Z_c$ states, and bottomonium-like, $Z_b$ states, represents a challenge since they can not be accommodated within the naive quark model. These charged states are good candidates of either tetraquark or molecular states and their observation motivated a vigorous theoretical activity. This is a rapidly evolving field with enormous amount of new experimental information. In this work, we review the current experimental progress and investigate various theoretical interpretations of these candidates of the multiquark states. The present review is written from the perspective of the QCD sum rules approach, where we present the main steps of concrete calculations and compare the results with other approaches and with experimental data.

90 pages, 27 figures; to be published in Journal of Physics G

References in corpus (312)

• Weak Decays Beyond Leading Logarithms
• Observation of a narrow charmonium-like state in exclusive B+ -> K+ pi+pi- J/psi decays
• Observation of a New Narrow Charmonium State in Exclusive B+-->K+ pi+pi- J/psi Decays
• Heavy quarkonium: progress, puzzles, and opportunities
• Hadronic molecules
• The hidden-charm pentaquark and tetraquark states
• Observation of $J/\psi p$ resonances consistent with pentaquark states in ${\Lambda }_b^0\to J/\psi K^{-}p$ decays
• Observation of a charged charmoniumlike structure in e+e- to pi+pi-J/psi at \sqrt{s}=4.26 GeV
• Multiquark Resonances
• Higher Charmonia
• Diquark-Antidiquarks with Hidden or Open Charm and the Nature of X(3872)
• Glueballs, Hybrids, Multiquarks. Experimental facts versus QCD inspired concepts
• Observation of a Broad Structure in the ${\pi }^{+}{\pi }^{-}J/\psi$ Mass Spectrum around 4.26 GeV/$c^2$
• Study of $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}J/\psi$ and Observation of a Charged Charmonium-like State at Belle
• Observation of the Narrow State $X(3872)\to J/\psi {\pi }^{+}{\pi }^{-}$ in $\bar{p}p$ Collisions at $\sqrt{s}=1.96 \TeV$
• The New Heavy Mesons: A Status Report
• Exotica
• Observation of a resonance-like structure in the pi^+- psi' mass distribution in exclusive B-->K pi^+- psi' decays
• Observation and Properties of the X(3872) Decaying to J/psi pi+ pi- in p-p(bar) Collisions at sqrt(s) = 1.96 TeV
• QCD and strongly coupled gauge theories: challenges and perspectives
• From the Deuteron to Deusons, an Analysis of Deuteronlike Meson-Meson Bound States
• Study of the B- --> J/psi K- pi+ pi- Decay and Measurement of the B- --> X(3872) K- Branching Fraction
• Observation of a charged charmoniumlike structure Z_c(4020) and search for the Z_c(3900) in e+e- to pi+pi-h_c
• Short Range Structure in the X(3872)
• Charmonium
• QCD at Low Energies
• Determination of the X(3872) meson quantum numbers
• 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
• Observation of the Charged Hadron $Z_c^{\pm }(3900)$ and Evidence for the Neutral $Z_c^0(3900)$ in $e^{+}{e}^{-}\to \pi \pi J/\psi$ at $\sqrt{s}=4170$ MeV
• Observation of a near-threshold omega-J/psi mass enhancement in exclusive B-->K omega J/psi decays
• New Charmonium States in QCD Sum Rules: a Concise Review
• Exotic Hadrons with Heavy Flavors -X, Y, Z and Related States-
• New Exotic Meson and Baryon Resonances from Doubly-Heavy Hadronic Molecules
• Higher Charmonia and X,Y,Z states with Screened Potential
• Evidence for a Narrow Near-Threshold Structure in the $J/\psi \varphi$ Mass Spectrum in $B^{+}\to J/\psi \varphi K^{+}$ Decays
• Experimental evidence for a light and broad scalar resonance in $D^{+}\to {\pi }^{-}{\pi }^{+}{\pi }^{+}$ decay
• Decoding the riddle of Y(4260) and $Z_c(3900)$
• Consequences of Heavy Quark Symmetries for Hadronic Molecules
• The Z(4430) and a New Paradigm for Spin Interactions in Tetraquarks
• The Exotic XYZ Charmonium-like Mesons
• The relation between the $\overline{\mathrm{MS}}$ and the on-shell quark mass at order ${\alpha }_s^3$
• Evidence of a Broad Structure at an Invariant Mass of 4.32 GeV/$c^2$ in the Reaction $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\psi (2S)$ Measured at BaBar
• Charmonium Options for the X(3872)
• Hadro-Charmonium
• Observation of a near-threshold enhancement in the e+e- -->Lambda_c+Lambda_c- cross section using initial-state radiation
• Precise measurement of the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}J/\psi$ cross section at center-of-mass energies from 3.77 to 4.60 GeV
• A Theory of Scalar Mesons
• Can the X(3872) be a 1^{++} four-quark state?
• The X(3872) boson: Molecule or charmonium
• Charmonium Decays of $Y(4260), psi(4160), and psi(4040)
• Observation of a new charmonium state in double charmonium production in e+ e- annihilation at \sqrt{s} ~ 10.6 GeV
• Four-Quark Hadrons: an Updated Review
• X(3872) and Other Possible Heavy Molecular States
• Masses, decays and mixings of gluonia in QCD
• Short-distance tachyonic gluon mass and 1/Q^2 corrections
• Observation of two resonance-like structures in the pi+ chi_c1 mass distribution in exclusive B0-bar --> K- pi+ chi_c1 decays
• Analysis of the Quantum Numbers $J^{PC}$ of the X(3872) Particle
• Observation of $J/\psi \varphi$ structures consistent with exotic states from amplitude analysis of $B^{+}\to J/\psi \varphi K^{+}$ decays
• Observation of $e^{+}{e}^{-}\to \gamma X(3872)$ at BESIII
• Are Y(4260) and {\rm Z${}_2^{+}$(4250)} ${\mathrm{D}}_1\mathrm{D}$ or ${\mathrm{D}}_0{\mathrm{D}}^{\ast }$ Hadronic Molecules?
• Evidence for the decay X(3872) --> J/psi omega
• Confirmation of the Y(4260) Resonance Production in ISR
• The Possible Interpretations of Y(4260)
• Diagnostic Decays of the X(3872)
• Evidence for X(3872) --> psi(2S) gamma in B+/- --> X(3872) K+/- decays, and a study of B --> ccbar gamma K
• Bounds on the width, mass difference and other properties of X(3872) --> pi+pi-J/psi decays
• Observation of a new charged charmoniumlike state in B -> J/psi K pi decays
• Observation of a Near-threshold $D^0{\bar{D}}^0{\pi }^0$ Enhancement in $B\to D^0{\bar{D}}^0{\pi }^{0}K$ Decay
• Gluon condensate in charmonium sum rules with 3-loop corrections
• QCD Sum Rules and Applications to Nuclear Physics
• Analysis of the X(3872), Z_c(3900) and Z_c(3885) as axial-vector tetraquark states with QCD sum rules
• Search for new charmonium states in the processes e+ e- --> J/psi D(*) D(*) at sqrt{s} ~ 10.6 GeV
• QCD Sum Rules for Skeptics
• Tetraquark Mesons in Large $N$ Quantum Chromodynamics
• Observation of X(3872) production in pp collisions at sqrt(s)= 7 TeV
• Experimental constraints on the spin and parity of the Z(4430)+
• New states above charm threshold
• Search for the Z(4430)^- at BABAR
• Heavy quarkonia mass-splittings in QCD: test of the $1/m$-expansion and estimates of $<{\alpha }_s{G}^2>$ and ${\alpha }_s$
• An overview of $XYZ$ new particles
• Observation of Y(3940) -> J/psi omega in B -> J/psi omega K at BABAR
• Evidence for the decay $X(3872)\to \psi (2S)\gamma$
• Model-independent evidence for $J/\psi p$ contributions to ${\Lambda }_b^0\to J/\psi p{K}^{-}$ decays
• Hadronic molecule structure of the Y(3940) and Y(4140)
• Light Flavour and Heavy Quark Spin Symmetry in Heavy Meson Molecules
• The Y(3940), Z(3930) and the X(4160) as dynamically generated resonances from the vector-vector interaction
• Exotic Hadrons from Heavy Ion Collisions
• Estimate for the X(3872) to gamma J/psi decay width
• The Vector and Axial-Vector Charmonium-like States
• Measurement of the X(3872) production cross section via decays to J/psi pi pi in pp collisions at sqrt(s) = 7 TeV
• Gluon Condensates and m_{c,b} from QCD-Moments and their ratios to Order alpha_s^3 and <G^4>
• Observation of a charmonium-like enhancement in the gamma gamma --> omega J/psi process
• Observation of a peaking structure in the J/psi phi mass spectrum from B(+/-) to J/psi phi K(+/-) decays
• QCD tests from $e^+e^- \rar I=1~$ hadrons data and implication on the value of ${\alpha }_s$ from $\tau$-decays
• Dalitz analysis of B --> K pi psi' decays and the Z(4430)+
• Possible assignments of the $X(3872)$, $Z_c(3900)$ and $Z_b(10610)$ as axial-vector molecular states
• Excited heavy tetraquarks with hidden charm
• Measurement of $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\psi (2S)$ via Initial State Radiation at Belle
• Measurement of the near-threshold $e^{+}{e}^{-}\to D\bar{D}$ cross section using initial-state radiation
• New Hadron States
• Amplitude analysis of $B^{+}\to J/\psi \varphi K^{+}$ decays
• Two-loop QCD corrections of the massive fermion propagator
• Decay constants of heavy-light vector mesons from QCD sum rules
• $Z_b$ and $Z_c$ Exotic States as Coupled Channel Cusps
• Y(4143) is probably a molecular partner of Y(3930)
• Study of $e^{+}{e}^{-}\to \omega {\chi }_{cJ}$ at center-of-mass energies from 4.21 to 4.42 GeV
• A J^PG=1++ Charged Resonance in the Y(4260) to pi+pi- J/psi Decay?
• Search for B+ --> X(3872) K+, X(3872) --> J/psi gamma
• An explanation of Belle states Z_b(10610) and Z_b(10650)
• Evidence for a new resonance and search for the Y(4140) in $\gamma \gamma \to \varphi J/\psi$
• Reinterpreting several narrow `resonances' as threshold cusps
• Observation of $Z_c(3900{)}^0$ in $e^{+}{e}^{-}\to {\pi }^0{\pi }^{0}J/\psi$
• Reanalysis of the $Y(3940)$, $Y(4140)$, $Z_c(4020)$, $Z_c(4025)$ and $Z_b(10650)$ as molecular states with QCD sum rules
• Could the near-threshold $XYZ$ states be simply kinematic effects?
• Observation of $e^{+}{e}^{-}\to {\pi }^0{\pi }^0{h}_c$ and a neutral charmoniumlike structure $Z_c(4020{)}^0$
• Study of the $B\to X(3872)(\to D^{\ast 0}{\bar{D}}^0)K$ decay
• Prediction of an $I=1$ $D{\bar{D}}^{\ast }$ state and relationship to the claimed $Z_c(3900)$, $Z_c(3885)$
• Power corrections to alpha_s(M_τ),|V_{us}| and m_s
• QCD Sum Rules for the X(3872) as a mixed molecule-charmoniun state
• Charmed Baryonium
• Charmonium Spectrum from Quenched Anisotropic Lattice QCD
• Gluon Condensates and m_b(m_b) from QCD-Exponential Moments at Higher Orders
• Is X(3872) a possible candidate of hybrid meson
• Evidence that the Y(4660) is a f_0(980)psi' bound state
• Quantum numbers of the $X(3872)$ state and orbital angular momentum in its ${\rho }^{0}J\psi$ decay
• Direct extraction of the chiral quark condensate and bounds on the light quark masses
• A study of B->X(3872) K, with X(3872)->J/Psi pi+ pi-
• $Z_c^{+}(3900)$ decay width in QCD sum rules
• Search for the X(4140) state in B+->J/psi phi K+ decays with the D0 detector
• Precision Measurement of the X(3872) Mass in J/psi pi+ pi- Decays
• Gluon condensates and c, b quark masses from quarkonia ratios of moments
• Is Z^+(4430) a loosely bound molecular state?
• $Y(4260)$ as the first $S$-wave open charm vector molecular state?
• Measurement of $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\psi (3686)$ from 4.008 to 4.600$\sim$GeV and observation of a charged structure in the ${\pi }^{\pm }\psi (3686)$ mass spectrum
• Determination of spin and parity of the $Z_c(3900)$
• One Explanation for the Exotic State Y(4260)
• On Deusons or Deuteronlike Meson-Meson Bound States
• Study of the X(3872) and Y(4260) in B0-->J/psi pi+ pi- K0 and B-->J/psi pi+ pi- K- decays
• The XYZ states revisited
• Narrow Tetraquarks at Large N
• Superconformal Baryon-Meson Symmetry and Light-Front Holographic QCD
• A New Hadron Spectroscopy
• Hints on the power corrections from current correlators in x-space
• Confirmation of a charged charmoniumlike state $Z_c(3885{)}^{\mp }$ in $e^{+}{e}^{-}\to {\pi }^{\pm }(D{\bar{D}}^{\ast }{)}^{\mp }$ with double $D$ tag
• Study of the $Z_c^{+}$ channel using lattice QCD
• $D^{\ast }D\pi$ form factor revisited
• Possible Molecular Structure of the Newly Observed Y(4260)
• Observation of the $Y(4140)$ structure in the $J/\psi \varphi$ Mass Spectrum in $B^{\pm }\to J/\psi \varphi K$ cays
• V-A hadronic tau decays : a laboratory for the QCD vacuum
• Couplings in coupled channels versus wave functions in the case of resonances: application to the two $\Lambda (1405)$ states
• Evidence of a resonant structure in the $e^{+}{e}^{-}\to {\pi }^{+}{D}^0{D}^{\ast -}$ cross section between 4.05 and 4.60 GeV
• Can Y(4140) be a $c\bar{c}s\bar{s}$ tetraquark ?
• Strong decays of molecular states Zc(+) and Zc'(+)
• Snapshots of Hadrons, or the Story of How the Vacuum Medium Determines the Properties of the Classical Mesons Which Are Produced, Live and Die in the QCD Vacuum
• Charm couplings and form factors in QCD sum rules
• Hadron Production via e+e- Collisions with Initial State Radiation
• Improved QCD sum rule study of $Z_c(3900)$ as a $\bar{D}{D}^{\ast }$ molecular state
• Duality between QCD Perturbative Series and Power Corrections
• Analysis of the $Z(4430)$ as the first radial excitation of the $Z_c(3900)$
• Strange-quark mass from combined e+e- and tau-decay data:test of the isospin symmetry and implications on epsilon'/εand m_{u,d}
• Search for the X(4140) state in B+ to J/psi phi K+ decays
• Mass spectra of Zc and Zb exotic states as hadron molecules
• Charged Exotic Charmonium States
• Measurement of the e+e- --> D0D*-pi+ cross section using initial-state radiation
• Issues and Opportunities in Exotic Hadrons
• Strong $Z_c^{+}(3900)\to J/\psi {\pi }^{+};{\eta }_c{\rho }^{+}$ decays in QCD
• Analysis of the Y(4140) with QCD sum rules
• A QCD sum rule calculation for the Y(4140) narrow structure
• Y(4140): Possible options
• Canonical Charmonium Interpretation for Y(4360) and Y(4660)
• Erratum: QCD sum rules study of the $J^{PC}=1^{--}$ charmonium $Y$ mesons
• The Y(4260) as a $J/\psi K\bar{K}$ system
• QCD sum rules study of the $J^{PC}=1^{--}$ charmonium $Y$ mesons
• QCD sum rules study of the meson Z^+(4430)
• Strange quark mass from e+e- revisited and present status of light quark masses
• $Z_c(3900)$ as a resonance from the $D{\bar{D}}^{\ast }$ interaction
• Charmonium Hybrid Production in Exclusive B Meson Decays
• Interpreting $Z_c(3900)$ and $Z_c(4025)/Z_c(4020)$ as charged tetraquark states
• QCD Parameters Correlations from Heavy Quarkonia
• Universal Effective Hadron Dynamics from Superconformal Algebra
• Search for Z_c^+(3900) in the 1^+- channel on the lattice
• Supersymmetry Across the Light and Heavy-Light Hadronic Spectrum
• Low-energy Scattering of $(D{\bar{D}}^{\ast }{)}^{\pm }$ System And the Resonance-like Structure $Z_c(3900)$
• Study of the $B{\bar{B}}^{\ast }/D{\bar{D}}^{\ast }$ bound states in a Bethe-Salpeter approach
• Electromagnetic Structure of the Z_c(3900)
• Model-independent determination of the gluon condensate in four-dimensional SU(3) gauge theory
• QSSR estimate of the $B_B$ parameter at next-to-leading order
• A fresh look into m_{c,b} and precise f_{D_(s),B_(s)} from heavy-light QCD spectral sum rules
• $D_s{D}^{\ast }$ molecule as an axial meson
• The $X(3872)\to J/\psi \gamma$ decay in the $D{\bar{D}}^{\ast }$ molecular picture
• Evidence for an ${\eta }_c(1S){\pi }^{-}$ resonance in $B^0\to {\eta }_c(1S)K^{+}{\pi }^{-}$ decays
• $X(3872)\to J/\psi {\pi }^{+}{\pi }^{-}$ and $X(3872)\to J/\psi {\pi }^{+}{\pi }^{-}{\pi }^0$ decay widths from QCD sum rules
• Threshold effect and π^\pm ψ(2S) peak
• $\{Q\bar{q}\}\{{\bar{Q}}^{{(}^{\prime })}q\}$ molecular states
• On $X(3872)$ production in high energy heavy ion collisions
• X(3872) and its production at hadron colliders
• The Spin-orbit force, recoil corrections and possible $B{\bar{B}}^{\ast }$ and $D{\bar{D}}^{\ast }$ molecular states
• Systematic uncertainties of hadron parameters obtained with QCD sum rules
• The Y(4260) as an omega chi_{c1} molecular state
• The hidden charm decay of Y(4140) by the rescattering mechanism
• Treating $Z_c(3900)$ and $Z(4430)$ as the ground-state and first radially excited tetraquarks
• Interpretation of $Z_c(4025)$ as the Hidden Charm Tetraquark States via QCD Sum Rules
• J/psi D*D* vertex from QCD sum rules
• Three-loop non-diagonal current correlators in QCD and NLO corrections to single-top-quark production
• Novel Charmonium and Bottomonium Spectroscopies due to Deeply Bound Hadronic Molecules from Single Pion Exchange
• Heavy-light current correlators at order ${\alpha }_s^2$ in QCD and HQET
• Analysis of the $Z_c(4200)$ as axial-vector molecule-like state
• Is $Z_c(3900)$ a molecular state
• Quark-Hadron Duality
• Mass spectra of four quark states in hidden charm sector
• Zc(4200)+ decay width as a charmonium-like tetraquark state
• XYZ-like Spectra from Laplace Sum Rule at N2LO in the Chiral Limit
• QCD Sum-Rule Interpretation of X(3872) with $J^{PC}=1^{++}$ Mixtures of Hybrid Charmonium and $\bar{D}{D}^{\ast }$ Molecular Currents
• Determining the upper limit of Gamma_{ee} for the Y(4260)
• Systematic studies of charmonium-, bottomonium-, and $B_c$-like tetraquark states
• Search for the $Z_1(4050{)}^{+}$ and $Z_2(4250{)}^{+}$ states in ${\bar{B}}^0\to {\chi }_{c1}{K}^{-}{\pi }^{+}$ and $B^{+}\to {\chi }_{c1}{K}_S^0{\pi }^{+}$
• $\{Q\bar{s}\}\{{\bar{Q}}^{{(}^{\prime })}s\}$ molecular states in QCD sum rules
• Parity of ${\Theta }^{+}$(1540) from QCD sum rules
• Relation between $T_{cc,bb}$ and $X_{c,b}$ from QCD
• Four-quark structure of Zc(3900), Z(4430) and Xb(5568) states
• Two-Hadron-Irreducible QCD Sum Rule for Pentaquark Baryon
• Cusps and Exotic Charmonia
• Spectra and decays of hybrid charmonia
• Hidden-Charm Tetraquarks and Charged Zc States
• Prediction of a $Z_c(4000)$ $D^{\ast }{\bar{D}}^{\ast }$ state and relationship to the claimed $Z_c(4025)$
• Hadronic Superpartners from Superconformal and Supersymmetric Algebra
• The meson $Z^{+}(4430)$ as a tetraquark state
• An Alternative Interpretation of X(3872)
• Probing the nature of Z_c states via the eta_c rho decay
• Supersymmetry Across the Light and Heavy-Light Hadronic Spectrum II
• On the nature of the X(3872) from QCD
• The bound state problem of S-wave heavy quark meson-aitimeson systems
• Updated Cross Section Measurement of $e^{+}{e}^{-}\to K^{+}{K}^{-}J/\psi$ and $K_S^0{K}_S^{0}J/\psi$ via Initial State Radiation at Belle
• $g_{NK\Lambda }$ and $g_{NK\Sigma }$ from QCD Sum Rules in the ${\gamma }_5{\sigma }_{\mu \nu }$ structure
• $B\to {\chi }_{c1}(1P,2P)K$ decays in QCD factorization and X(3872)
• Radiative decays of the neutral $Z_c(3900)$
• Hadronic molecules with both open charm and bottom
• Can the ${\pi }^{+}{\chi }_{c1}$ resonance structures be $D^{\ast }{\bar{D}}^{\ast }$ and $D_1\bar{D}$ molecules?
• QCD sum rule calculation for the charmonium-like structures in the J/psi phi and J/psi omega invariant mass spectra
• Mass spectra for $qc\bar{q}\bar{c}$, $sc\bar{s}\bar{c}$, $qb\bar{q}\bar{b}$, $sb\bar{s}\bar{b}$ tetraquark states with $J^{PC}=0^{++}$ and $2^{++}$
• A QCD sum rule calculation of the $X^{\pm }(5568)\to B_s^0{\pi }^{\pm }$ decay width
• Low-energy $D^{\ast +}{D}_1^0$ Scattering and the Resonance-like Structure $Z^{+}(4430)$
• Mass Spectrum of Heavy Quarkonium Hybrids
• Improved light quark masses from pseudoscalar sum rules
• Scalar, axial-vector and tensor resonances from the rho D^*, omega D^* interaction in the hidden gauge formalism
• Do the QCD sum rules support four-quark states?
• Predicition for the decay width of a charged state near the $D_s{\bar{D}}^{\ast }/D_s^{\ast }\bar{D}$ threshold
• Mixings of 4-quark components in light non-singlet scalar mesons in QCD sum rules
• Width of exotics from QCD sum rules : tetraquarks or molecules?
• The $P$-wave $[cs][\bar{c}\bar{s}]$ tetraquark state: Y(4260) or Y(4660)?
• $Z_c(3900)$ as a $D{\bar{D}}^{\ast }$ molecule from the pole counting rule
• Radiative decay of the X(3872) as a mixed molecule-charmonium state in QCD Sum Rules
• The string-junction picture of multiquark states: an update
• Observation of e+e- to K+K-J/psi via Initial State Radiation at Belle
• Gluon Condensate from Superconvergent QCD Sum Rule
• Lowest vector tetraquark states: $Y(4260/4220)$ or $Z_c(4100)$
• Semileptonic D decay into scalar mesons: a QCD sum rule approach
• $J/\psi$ dissociation by pions in QCD
• Exotic $1^{--}$ States in QCD Sum Rules
• Radiative decays of the Y(3940), Z(3930) and the X(4160) as dynamically generated resonances
• Evidence for $Z_c^{\pm }(3900)$ in semi-inclusive decays of $b$-flavored hadrons
• Systematic study of $Z_c^{+}$ family from quark model's perspective
• Hadronic Spectrum - Multiquark States
• Supersymmetry in the Double-Heavy Hadronic Spectrum
• Another tetraquark structure in the ${\pi }^{+}{\chi }_{c1}$ invariant mass distribution
• Radiative and dilepton decays of the hadronic molecule Zc(3900)+
• $D^{\ast }{\bar{D}}^{\ast }$ molecule interpretation of $Z_c(4025)$
• Axial Vector $J^{PC}=1^{++}$ Charmonium and Bottomonium Hybrid Mass Predictions with QCD Sum-Rules
• Resolving the puzzling decay patterns of charged $Z_c$ and $Z_b$ states
• ${\mathrm{Z}}^{+}(4430)$ and Analogous Heavy Flavor States
• Analysis of the $B^{+}\to J/\psi \varphi K^{+}$ data at low $J/\psi \varphi$ invariant masses and the $X(4140)$ and $X(4160)$ resonances
• Relating $D^{\ast }{\bar{D}}^{\ast }$ currents with $J^{\pi }=0^{+},1^{+}$ and $2^{+}$ to $Z_c$ states
• Hidden charmed states and multibody color flux-tube dynamics
• QCD Sum Rules for the production of the X(3872) as a mixed molecule-charmonium state in B meson decay
• Interference effects in the X(4260) signal
• Resonance $Y(4660)$ as a vector tetraquark and its strong decay channels
• Could $Z_c(4025)$ be a $J^P=1^{+}$ $D^{\ast }\overline{D^{\ast }}$ molecular state?
• Photoproduction of the charged charmoniumlike $Z_c^{+}(4200)$
• Search for the $Y(4140)$ via $e^{+}{e}^{-}\to \gamma \varphi J/\psi$ at $\sqrt{s}=$ 4.23, 4.26 and 4.36 GeV
• XYZ-SU3 Breakings from Laplace Sum Rules at Higher Orders
• Heavy Tetraquarks in the Diquark-Antidiquark Picture
• Possible new resonance at the $D^{\ast }{\bar{D}}^{\ast }$ threshold in $e^{+}{e}^{-}$ annihilation
• Production of exotic charmonium in $\gamma \gamma$ interactions at hadronic colliders
• Y(4260) as a mixed charmonium-tetraquark state
• X(3872): propagating in a dense medium
• Renormalon Subtraction from the Average Plaquette and the Gluon Condensate
• Pentaquark Decay Width in QCD Sum Rules
• Exotic Four Quark Matter: $Z_1(4475)$
• $Z_c(4100)$ and $Z_c(4200)$ as hadrocharmonium
• Molecular Interpretation of the Supercharmonium State Z(4475)
• Light Scalar Meson sigma(600) in QCD Sum Rule with Continuum
• B^0_{d,s} - \bar{B}^0_{d,s} mass-differences from QCD spectral sum rules
• On the $\pi \pi$ contribution to the QCD sum rules for the light tetraquark
• Reanalysis of the $e^{+}{e}^{-}\to (D^{\ast }{\bar{D}}^{\ast }{)}^{\pm }{\pi }^{\mp }$ reaction and the claim for the $Z_c(4025)$ resonance
• Meson-Hybrid Mixing in $J^{PC}=1^{++}$ Heavy Quarkonium from QCD Sum-Rules
• Can the X(4350) narrow structure be a $1^{-+}$ exotic state?
• X(3872) and Its Heavy Quark Spin Symmetry Partners in QCD Sum Rules
• A Comparative Study of Pentaquark Interpolating Currents
• Observation of $e^{+}{e}^{-}\to \varphi {\chi }_{c1}$ and $\varphi {\chi }_{c2}$ at $\sqrt{s}$=4.600 GeV
• Search for resonances decaying to eta_c pi+ pi- in two-photon interactions
• Exploring the $D^{\ast }\rho$ system within QCD sum rules
• Understanding close-lying exotic charmonia states within QCD sum rules
• Y(3940) as a Mixed Charmonium-Molecule State
• Meson loops and the $g_{D^{\ast }D\pi }$ coupling
• Factorization breaking of four-quark condensates in the Nambu Jona Lasinio model
• Discovery potential for the neutral charmoniumlike $Z^0(4200)$ by $\bar{p}p$ annihilation
• Introduction to QCD sum rules
• Study on decays of $Z_c(4020)$ and $Z_c(3900)$ into $h_c+\pi$
• Light-front holographic QCD with generic dilaton profile
• Few-Body Systems Composed of Heavy Quarks

Cited by in corpus (75)

• The $XYZ$ states: experimental and theoretical status and perspectives
• An updated review of the new hadron states
• Analysis of the $P_c(4312)$, $P_c(4440)$, $P_c(4457)$ and related hidden-charm pentaquark states with QCD sum rules
• Doubly-hidden scalar heavy molecules and tetraquarks states from QCD at NLO
• Newly observed exotic doubly charmed meson $T_{cc}^{+}$
• Magnetic dipole moments of the hidden-charm pentaquark states: $P_c(4440)$, $P_c(4457)$ and $P_{cs}(4459)$
• Spectrum of the Hidden-Bottom and the Hidden-Charm/Strange Exotics in the Dynamical Diquark Model
• Study of charmonium-like and fully-charm tetraquark spectroscopy
• $X_{0,1}$(2900) and $(D^{-}{K}^{+})$ invariant mass from QCD Laplace sum rules at NLO
• Analysis of the $Z_{cs}(3985)$ as the axialvector tetraquark state
• The production of doubly charmed exotic hadrons in heavy ion collisions
• Z_c -like spectra from QCD Laplace sum rules at NLO
• New scalar resonance $X_0(2900)$ as a ${\overline{D}}^{\ast }{K}^{\ast }$ molecule: Mass and width
• Identifying the ${\Xi }_b(6227)$ and ${\Sigma }_b(6097)$ as $P$-wave bottom baryons of $J^P=3/2^{-}$
• Analysis of the hidden-charm tetraquark mass spectrum with the QCD sum rules
• Double-charm tetraquark under the complex scaling method
• Landau equation and QCD sum rules for the tetraquark molecular states
• Analysis of the $X(3960)$ and related tetraquark molecular states via the QCD sum rules
• Four-quark states with charm quarks in a two-body Bethe-Salpeter approach
• Tetraquarks in large-$N_c$ QCD
• Decay properties of $P$-wave heavy baryons accompanied by vector mesons within light-cone sum rules
• The lineshape of the compact fully heavy tetraquark
• Exploring the electromagnetic properties of the ${\Xi }_c^{(\prime ,\ast )}{\bar{D}}_s^{\ast }$ and ${\Omega }_c^{(\ast )}{\bar{D}}_s^{\ast }$ molecular states
• Revealing the nature of hidden charm pentaquarks with machine learning
• Partial decay widths of $P_c(4312)$ as a $\bar{D}{\Sigma }_c$ molecular state
• NLO results with operator mixing for fully heavy tetraquarks in QCD sum rules
• Vector resonance $X_1(2900)$ and its structure
• Monte-Carlo Based QCD Sum Rules Analysis of $X_0(2900)$ and $X_1(2900)$
• Analysis of the fully-heavy pentaquark states via the QCD sum rules
• Semileptonic and nonleptonic decays of the axial-vector tetraquark $T_{bb;\overline{u}\overline{d}}^{-}$
• Decipher the width of the $X(3872)$ via the QCD sum rules
• Radiative decays and magnetic moments of the predicted $B_c$-like molecules
• Radiative decays of the spin-$2$ partner of $X(3872)$
• Insights into $Z_b(10610)$ and $Z_b(10650)$ from dipion transitions from ${\rm Y}(10860)$
• Tetraquark-adequate QCD sum rules for quark-exchange processes
• Triangle singularity appearing as an $X(3872)$-like peak in $B\to (J/\psi {\pi }^{+}{\pi }^{-})K\pi$
• Improved XTZ masses and mass ratios from Laplace Sum Rules at NLO
• Fully-heavy hexaquark states via the QCD sum rules
• The interplay between compact and molecular structures in tetraquarks
• NLO effects for ${\Omega }_{QQQ}$ Baryons in QCD Sum Rules
• Analysis of the pseudoscalar hidden-charm tetraquark states with the QCD sum rules
• Light axial-vector and vector resonances $X(2100)$ and $X(2239)$
• Resonance $X(4630)$
• Production of the $X(4014)$ as the spin-2 partner of $X(3872)$ in $e^{+}{e}^{-}$ collisions
• $P$-wave charmonium contribution to hidden-charm states from reanalysis of lattice QCD data
• Is the resonance $X_0(2900)$ a ground-state or radially excited scalar tetraquark $[ud][\overline{c}\overline{s}]$?
• Decay modes of the scalar exotic meson $T_{bs;\overline{u}\overline{d}}^{-}$
• Analysis of the vector hidden-charm-hidden-strange tetraquark states with implicit P-waves
• Covalent hadronic molecules induced by shared light quarks
• Analysis of the tetraquark and hexaquark molecular states with the QCD sum rules
• Study of exotic hadrons with machine learning
• Triply-charmed hexaquark states with the QCD sum rules
• $X$ structures in $B^{+}\to J/\psi \varphi K^{+}$ as one-loop and double-triangle threshold cusps
• Discover the GellMann-Okubo formula with machine learning
• Probing exotic $J^{PC}$ resonances from deeply bound charmoniumlike molecules: Insights for identifying exotic hadrons
• Two-pion exchange for coupled-channel scattering of two heavy mesons
• Investigating the Isospin Property of $T_{cc}^{+}$ from its Dalitz Plot Distribution
• Applications of Diagrammatic Renormalization Methods in QCD Sum-Rules
• Modifications on parameters of $Z(4430)$ in a dense medium
• Next-to-Leading Order (NLO) Perturbative Effects in QCD Sum-Rule Analyses of Light Tetraquark Systems: A Case Study in the Scalar-Isoscalar Channel
• $Z_c$ and $Z_{cs}$ systems with operator mixing at NLO in QCD sum rules
• On the emergence of heavy quark spin symmetry breaking in heavy quarkonium decays
• The ground states and first radial excitations of the vector tetraquark states with explicit P-waves via the QCD sum rules
• Revisiting light-flavor diquarks in the inverse matrix method of QCD sum rules
• Strong decays of the vector tetraquark states with the masses about $4.5\mathrm{GeV}$ via the QCD sum rules
• Pole analysis for the $D^{\ast }\bar{K}$-$D\overline{K^{\ast }}$ coupled-channel system
• Mixing of X and Y states from QCD Sum Rules analysis
• Analysis of the hidden-charm pentaquark candidates in the $J/\psi p$ mass spectrum with QCD sum rules
• Production of hidden-heavy and double-heavy hadronic molecules at the $Z$ factory of CEPC
• Two-body strong decays of the hidden-charm tetraquark molecular states via the QCD sum rules
• Baryons and baryoniums in the perspective of QCD sum rules
• New Types of Hydrogenlike matter Composed of Electron(s) and Meson(s)
• Insights into the exotic charged states $Z_b(10610)$ and $Z_b(10650)$ from their photoproduction off nuclei
• Meson scattering and tetraquarks in two-dimensional QCD
• Strange pentaquark molecules in QCD sum rules