A New Hadron Spectroscopy

Abstract

QCD-motivated models for hadrons predict an assortment of "exotic" hadrons that have structures that are more complex than the quark-antiquark mesons and three-quark baryons of the original quark-parton model. These include pentaquark baryons, the six-quark H-dibaryon, and tetraquark, hybrid and glueball mesons. Despite extensive experimental searches, no unambiguous candidates for any of these exotic configurations have been identified. On the other hand, a number of meson states, one that seems to be a proton-antiproton bound state, and others that contain either charmed-anticharmed quark pairs or bottom-antibottom quark pairs, have been recently discovered that neither fit into the quark-antiquark meson picture nor match the expected properties of the QCD-inspired exotics. Here I briefly review results from a recent search for the H-dibaryon, and discuss some properties of the newly discovered states --the proton-antiproton state and the so-called XYZ mesons-- and compare them with expectations for conventional quark-antiquark mesons and the predicted QCD-exotic states.

34 pages, 22 figures, a review article that will appear in Frontiers of Physics

References in corpus (129)

• The Cosmological Parameters 2006
• Big-Bang nucleosynthesis (Particle Data Group mini-review)
• 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
• Universality in Few-body Systems with Large Scattering Length
• Design and Construction of the BESIII Detector
• QCD Factorization for $B\to \pi \pi$ Decays: Strong Phases and CP Violation in the Heavy Quark Limit
• QCD factorization for exclusive, non-leptonic B meson decays: General arguments and the case of heavy-light final states
• Observation of a charged charmoniumlike structure in e+e- to pi+pi-J/psi at \sqrt{s}=4.26 GeV
• Evidence for Narrow S=+1 Baryon Resonance in Photo-production from Neutron
• Higher Charmonia
• Diquark-Antidiquarks with Hidden or Open Charm and the Nature of X(3872)
• 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
• Exotic Anti-Decuplet of Baryons: Prediction from Chiral Solitons
• Observation of the Narrow State $X(3872)\to J/\psi {\pi }^{+}{\pi }^{-}$ in $\bar{p}p$ Collisions at $\sqrt{s}=1.96 \TeV$
• Observation of two charged bottomonium-like resonances in Y(5S) decays
• 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
• Isospin breaking of the narrow charmonium state of Belle at 3872 MeV as a deuson
• 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)
• 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 a near-threshold omega-J/psi mass enhancement in exclusive B-->K omega J/psi decays
• Couplings in coupled channels versus wave functions: application to the X(3872) resonance
• Evidence for a Narrow Near-Threshold Structure in the $J/\psi \varphi$ Mass Spectrum in $B^{+}\to J/\psi \varphi K^{+}$ Decays
• Observation of a charged (DD*bar)- mass peak in e+e- --> pi+ (DD*bar)- at Ecm=4.26 GeV
• Observation of a near-threshold enhancement in th p pbar mass spectrum from radiative J/psi-->gamma p pbar decays
• Decoding the riddle of Y(4260) and $Z_c(3900)$
• Bound H-dibaryon in Flavor SU(3) Limit of Lattice QCD
• Observation of a charged charmoniumlike structure in $e^{+}{e}^{-}\to (D^{\ast }{\bar{D}}^{\ast }{)}^{\pm }{\pi }^{\mp }$ at $\sqrt{s}=4.26$GeV
• The Z(4430) and a New Paradigm for Spin Interactions in Tetraquarks
• The Exotic XYZ Charmonium-like Mesons
• 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
• Excited and exotic charmonium spectroscopy from lattice QCD
• Exotic QQ\qbar\qbar States in QCD
• Observation of a near-threshold enhancement in the e+e- -->Lambda_c+Lambda_c- cross section using initial-state radiation
• Evidence for a Bound H-dibaryon from Lattice QCD
• Measurements of the Cross Section for e+e- -> hadrons at Center-of-Mass Energies from 2 to 5 GeV
• 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
• Molecular States of Heavy Quark Mesons
• 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
• Pion Interactions in the X(3872)
• Is the X(3872) Production Cross Section at Tevatron Compatible with a Hadron Molecule Interpretation?
• Observation of $e^{+}{e}^{-}\to \gamma X(3872)$ at BESIII
• Evidence for the decay X(3872) --> J/psi omega
• Confirmation of the Y(4260) Resonance Production in ISR
• 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 Near-threshold $D^0{\bar{D}}^0{\pi }^0$ Enhancement in $B\to D^0{\bar{D}}^0{\pi }^{0}K$ Decay
• Observation of a resonance X(1835) in J/ψ--> γπ^+ π^- η^{\prime}
• Suppressed decay into open charm for the Y(4260) being an hybrid
• 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
• Observation of X(3872) production in pp collisions at sqrt(s)= 7 TeV
• Experimental constraints on the spin and parity of the Z(4430)+
• Search for the Z(4430)^- at BABAR
• Observation of Y(3940) -> J/psi omega in B -> J/psi omega K at BABAR
• Evidence for the decay $X(3872)\to \psi (2S)\gamma$
• The Y(3940), Z(3930) and the X(4160) as dynamically generated resonances from the vector-vector interaction
• Observation of new resonances decaying to $D\pi$ and $D^{\ast }\pi$ in inclusive $e^{+}{e}^{-}$ collisions near $\sqrt{s}=$10.58 GeV
• Observation of a new D_sJ meson in B+->D0BD0K+ decays
• Confirmation of the X(1835) and observation of the resonances X(2120) and X(2370) in J/psi->gamma pi^+pi^-eta'
• Study of Resonances in Exclusive B Decays to Dbar(*)D(*)K
• First observation of the P-wave spin-singlet bottomonium states h_b(1P) and h_b(2P)
• Observation of $X(3872)\to J/\psi \gamma$ and search for $X(3872)\to {\psi }^{\prime }\gamma$ in B decays
• Observation of a peaking structure in the J/psi phi mass spectrum from B(+/-) to J/psi phi K(+/-) decays
• Observation of a charmonium-like enhancement in the gamma gamma --> omega J/psi process
• Dalitz analysis of B --> K pi psi' decays and the Z(4430)+
• Isospin breaking effects in the X(3872) resonance
• Line Shapes of the X(3872)
• Measurement of the near-threshold $e^{+}{e}^{-}\to D\bar{D}$ cross section using initial-state radiation
• New Hadron States
• A J^PG=1++ Charged Resonance in the Y(4260) to pi+pi- J/psi Decay?
• Near threshold enhancement of the ppbar mass spectrum in J/Psi decay
• Evidence for a new resonance and search for the Y(4140) in $\gamma \gamma \to \varphi J/\psi$
• Study of the $B\to X(3872)(\to D^{\ast 0}{\bar{D}}^0)K$ decay
• Determination of the $\psi (3770)$, $\psi (4040)$, $\psi (4160)$ and $\psi (4415)$ resonance parameters
• Measurement of the near-threshold $e^{+}{e}^{-}\to D^{(\ast )\pm }D{}^{\ast \mp }$ cross section using initial-state radiation
• Study of the Exclusive Initial-State Radiation Production of the $D\bar{D}$ System
• Tetraquark Interpretation of the Charged Bottomonium-like states Z_b^+-(10610) and Z_b^+-(10650) and Implications
• Precision Measurement of the X(3872) Mass in J/psi pi+ pi- Decays
• One-pion-exchange final-state-interaction and the pbar p near threshold enhancement in J/psi -> gamma pbar p decays
• Observation of the chi_c2(2P) meson in the reaction gamma gamma -> D Dbar at BABAR
• Search for a Charged Partner of the X(3872) in the B Meson Decay B --> X- K, X- --> J/psi pi- pi0
• Where is the χ_{c0}(2P)?
• Measurement of $b$ hadron masses in exclusive $J/\psi$ decays with the CDF detector
• Study of X(3915) --> J/ψω in two-photon collisions
• A case for hidden $b\bar{b}$ tetraquarks based on $e^{+}{e}^{-}\to b\bar{b}$ cross section between $\sqrt{s}=10.54$ and 11.20 GeV
• On the hidden charm state at 3872 MeV
• Spin-Parity Analysis of ppbar Mass Threshold Structure in J/psi and psi' Radiative Decays
• Search for the ${\Theta }^{+}$ pentaquark in the reaction $\gamma d\to p{K}^{-}{K}^{+}n$
• Heavy quark spin selection rule and the properties of the X(3872)
• Tetraquark interpretation of the BELLE data on the anomalous ${\rm Y}(1S){\pi }^{+}{\pi }^{-}$ and ${\rm Y}(2S){\pi }^{+}{\pi }^{-}$ production near the ${\rm Y}(5S)$ resonance
• Observation of $\psi (4415)\to D\bar{D}{}_2^{\ast }(2460)$ decay using initial-state radiation
• Search for the X(4140) state in B+ to J/psi phi K+ decays
• Measurement of the e+e- --> D0D*-pi+ cross section using initial-state radiation
• Observation of B+ -> p pbar pi+, B0 -> p pbar K0, and B+ -> p pbar K*+
• Ambiversion of X(3872)
• Observation of an enhancement in $e^{+}{e}^{-}\to {\rm Y}(1S){\pi }^{+}{\pi }^{-}$, ${\rm Y}(2S){\pi }^{+}{\pi }^{-}$, and ${\rm Y}(3S){\pi }^{+}{\pi }^{-}$ production around $\sqrt{s}=10.89$ GeV at Belle
• Observation of an enhancement in e+e- to Upsilon(1S)pi+pi-, Upsilon(2S)pi+pi-, and Upsilon(3S)pi+pi- production near sqrt{s}=10.89 GeV at Belle
• First Observation of the Zb0(10610) in a Dalitz Analysis of Y(5S) -> Y(nS) pi0 pi0
• The $X(3872)\to J/\psi \gamma$ decay in the $D{\bar{D}}^{\ast }$ molecular picture
• X(3872) is not a true molecule
• Radiative Decays of the Upsilon(1S) to a Pair of Charged Hadrons
• Search for an H-dibaryon with mass near 2m_Lambda in Y(1S) and Y(2S) decays
• Determining the upper limit of Gamma_{ee} for the Y(4260)
• Search for the $Z_1(4050{)}^{+}$ and $Z_2(4250{)}^{+}$ states in ${\bar{B}}^0\to {\chi }_{c1}{K}^{-}{\pi }^{+}$ and $B^{+}\to {\chi }_{c1}{K}_S^0{\pi }^{+}$
• Search for a new bottomonium state decaying to Upsilon(1S) pi+ pi- in pp collisions at sqrt(s) = 8 TeV
• Searching for the Bottom Counterparts of X(3872) and Y(4260) via ${\pi }^{+}{\pi }^{-}{\rm Y}$
• Interpretations for the X(4160) observed in the double charm production at B factories
• Production of the X(3870) at the Upsilon(4S) by the Coalescence of Charm Mesons
• Study of Jψdecaying into ωp \bar p
• Novel charmonium-like structures in the $J/\psi \varphi$ and $J/\psi \omega$ invariant mass spectra
• Are the $X$(4160) and $X$(3915) charmonium states?
• Search for the ${\Theta }^{+}$ pentaquark via the ${\pi }^{-}p\to K^{-}X$ reaction at 1.92 GeV/$c$
• Observation of a structure at 1.84 GeV/c${}^2$ in the $3({\pi }^{+}{\pi }^{-})$ mass spectrum in $J/\psi \to \gamma 3({\pi }^{+}{\pi }^{-})$ decays
• Measurement of the B -> Dbar(*)D(*)K branching fractions
• Experimental Review of Structures in the $J/\psi \varphi$ Mass Spectrum
• Charged charmonium-like states as rescattering effects in B -> D_sJ D^(*) decays

Cited by in corpus (67)

• Hadronic molecules
• The hidden-charm pentaquark and tetraquark states
• Heavy-Quark QCD Exotica
• An updated review of the new hadron states
• Heavy-quark symmetry implies stable heavy tetraquark mesons $Q_i{Q}_j{\bar{q}}_k{\bar{q}}_l$
• Chiral perturbation theory for heavy hadrons and chiral effective field theory for heavy hadronic molecules
• Observation of a near-threshold structure in the $K^{+}$ recoil-mass spectra in $e^{+}{e}^{-}\to K^{+}(D_s^{-}{D}^{\ast 0}+D_s^{\ast -}{D}^0)$
• A non-relativistic model for the $[cc][\bar{c}\bar{c}]$ tetraquark
• Weak decays of heavy hadrons into dynamically generated resonances
• Charmonium spectrum and their electromagnetic transitions with higher multipole contributions
• QCD Sum Rules Approach to the $X,Y$ and $Z$ States
• X(3872) and Y(4140) using diquark-antidiquark operators with lattice QCD
• Search for structure in the $B_s^0{\pi }^{\pm }$ invariant mass spectrum
• Diffusion Monte Carlo calculations of fully-heavy (multiquark) bound states
• Heavy hadronic molecules with pion exchange and quark core couplings: a guide for practitioners
• Observation of a neutral charmoniumlike state $Z_c(4025{)}^0$ in $e^{+}{e}^{-}\to (D^{\ast }{\bar{D}}^{\ast }{)}^0{\pi }^0$
• Mass spectra of Zc and Zb exotic states as hadron molecules
• Observation of a Neutral Structure near the $D{\bar{D}}^{\ast }$ Mass Threshold in $e^{+}{e}^{-}\to (D{\bar{D}}^{\ast }{)}^0{\pi }^0$ at $\sqrt{s}$ = 4.226 and 4.257 GeV
• Luminosities and energies of $e^{+}{e}^{-}$ collision data taken between $\sqrt{s}$=4.612 GeV and 4.946 GeV at BESIII
• Spin structure of heavy-quark hybrids
• General considerations on the nature of $Z_b(10610)$ and $Z_b(10650)$ from their pole positions
• Analysis of the $Z_c(4200)$ as axial-vector molecule-like state
• QCD spin effects in the heavy hybrid potentials and spectra
• Systematic studies of charmonium-, bottomonium-, and $B_c$-like tetraquark states
• Spectrum and rearrangement decays of tetraquark states with four different flavors
• Can $X(5568)$ be described as a $B_s\pi$, $B\bar{K}$ resonant state?
• Spectroscopy of ${\mathbf{B}}_{\mathbf{c}}$ mesons and the possibility of finding exotic ${\mathbf{B}}_{\mathbf{c}}$-like structures
• Strong decays of higher charmonium states into open-charm meson pairs
• A tetraquark or not a tetraquark: A holography inspired stringy hadron (HISH) perspective
• A model-independent confirmation of the $Z(4430{)}^{-}$ state
• Galilean-Invariant XEFT
• Hadronic Loops versus Factorization in EFT calculations of $X(3872)\to {\chi }_{cJ}{\pi }^0$
• $K^{\ast }$ mesons with hidden charm arising from $KX(3872)$ and $K{Z}_c(3900)$ dynamics
• Excited mesons, baryons, glueballs and tetraquarks: Predictions of the Holography Inspired Stringy Hadron model
• Doing spin physics with unpolarized particles
• Narrow exotic tetraquark mesons in large-$N_c$ QCD
• Open-flavor charmed/bottom $sq\bar{q}\bar{Q}$ and $qq\bar{q}\bar{Q}$ tetraquark states
• How to understand the underlying structures of $X(4140)$, $X(4274)$, $X(4500)$ and $X(4700)$
• $Z_c(3900)$: Confronting theory and lattice simulations
• Observation of the ${\chi }_{b1}$(3P) and ${\chi }_{b2}$(3P) and measurement of their masses
• Tetraquark and two-meson states at large $N_{\mathrm{c}}$
• Pentaquark states with the $QQQq\bar{q}$ configuration in a simple model
• Fully-charm and -bottom pentaquarks in a Lattice-QCD inspired quark model
• Towards the discovery of novel $B_c$ states: radiative and hadronic transitions
• Using $X(3823)\to J/\psi {\pi }^{+}{\pi }^{-}$ to identify coupled-channel effects
• Heavy hybrid decays to quarkonia
• Generating a resonance-like structure in the reaction $B_c\to B_s\pi \pi$
• Tetraquarks in holographic QCD
• Twisted particle collisions: a new tool for spin physics
• Weak Decays of Stable Open-bottom Tetraquark by SU(3) Symmetry Analysis
• Two-Body Strong Decay of the 2P and 3P Charmonium states
• Diabatic description of bottomoniumlike mesons
• The impact of $S$-wave thresholds $D_{s1}{\bar{D}}_s+c.c.$ and $D_{s0}{\bar{D}}_s^{\ast }+c.c.$ on vector charmonium spectrum
• Instanton effects on the heavy-quark static potential
• Tri-meson bound state $BB{B}^{\ast }$ via delocalized $\pi$~Bond
• Charmonium description from a generalized screened potential model
• Instanton effects on charmonium states
• Understanding close-lying exotic charmonia states within QCD sum rules
• Bottomonium spectrum with a Dirac potential model in the momentum space
• Binding of the three-hadron $D{D}^{\ast }K$ system from the lattice effective field theory
• $Z_b(10610)$ in a hadronic medium
• Light-by-light forward scattering sum rules for charmonium states
• The Production of $X(3940)$ and $X(4160)$ in $B_c$ decays
• Schottky Anomaly and Hadronic Spectrum
• Strong Decays of Charmonia
• The effects of charmonium on the properties of the $1^{++}$ hidden charm poles in effective field theory
• New Types of Hydrogenlike matter Composed of Electron(s) and Meson(s)