Charmonium-like States Research Articles

Experimental Road to a Charming Family of Tetraquarks...and Beyond

Abstract Discovery of the X(3872) meson in 2003 ignited intense interest in exotic (neither $q\bar{q}$ nor $qqq$) hadrons, but a $c\bar{c}$ interpretation of this state was difficult to exclude. An unequivocal exotic was discovered in the $Z_c(3900)^+$ meson—a charged charmonium-like state. A variety of models of exotic structure have been advanced but consensus is elusive. The grand lesson from heavy quarkonia was that heavy quarks bring clarity. Thus, the recently reported triplet of all-charm tetraquark candidates—$X(6600)$, $X(6900)$, and $X(7100)$—decaying to $J/\psi\,J/\psi$ is a great boon, promising important insights. We review some history of exotics, chronicle the road to prospective all-charm tetraquarks, discuss in some detail the divergent modeling of $J/\psi\,J/\psi$ structures, and offer some inferences about them. These states form a Regge trajectory and appear to be a family of radial excitations. A reported, but unexplained, threshold excess could hint at a fourth family member. We close with a brief look at a step beyond: all-bottom tetraquarks.

Observation of New Charmonium or Charmoniumlike States in B^{+}→D^{*±}D^{∓}K^{+} Decays.

A study of resonant structures in B^{+}→D^{*+}D^{-}K^{+} and B^{+}→D^{*-}D^{+}K^{+} decays is performed, using proton-proton collision data at center-of-mass energies of sqrt[s]=7, 8, and 13TeV recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb^{-1}. A simultaneous amplitude fit is performed to the two channels with contributions from resonances decaying to D^{*-}D^{+} and D^{*+}D^{-} states linked by C parity. This procedure allows the C parities of resonances in the D^{*±}D^{∓} mass spectra to be determined. Four charmonium or charmoniumlike states are observed decaying into D^{*±}D^{∓}: η_{c}(3945), h_{c}(4000), χ_{c1}(4010), and h_{c}(4300), with quantum numbers J^{PC} equal to 0^{-+}, 1^{+-}, 1^{++}, and 1^{+-}, respectively. At least three of these states have not been observed previously. In addition, the existence of the T_{c[over ¯]s[over ¯]0}^{*}(2870)^{0} and T_{c[over ¯]s[over ¯]1}^{*}(2900)^{0} resonances in the D^{-}K^{+} mass spectrum, already observed in the B^{+}→D^{+}D^{-}K^{+} decay, is confirmed in a different production channel.

Charmonia in an unquenched quark model

In this work, we study the charmonium spectrum within an unquenched quark model including coupled-channel effects. In couple-channel calculations, we include all of the opened charmed meson channels with the once-subtracted method, meanwhile we adopt a suppressed factor to soften the hard vertices given by the P03 model in the high momentum region. We obtain a good description of both the masses and widths for the well-established states in the charmonium spectrum. Furthermore, we give predictions for the higher S-, P-, and D-wave charmonium states up to mass region of ∼5.0 GeV. The magnitude of mass shifts due to the coupled-channel effects is estimated to be about 10s MeV. Although many decay channels are opened for the higher charmonium states, they are relatively narrow states. Their widths scatter in the range of ∼10s–100 MeV. Many charmoniumlike states, such as χc1(4274), χc0(3915), χc0(4500), χc0(4700), X(4160), X(4350), Y(4500), and ψ(4660)/Y(4710), can be accommodated by the charmonium spectrum when the unquenched coupled-channel effects are carefully considered. Published by the American Physical Society 2024

Predicting isovector charmonium-like states from X(3872) properties

Using chiral effective field theory, we predict that there must be isovector charmonium-like DD¯∗\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ D{\\overline{D}}^{\\ast } $$\\end{document} hadronic molecules with JPC = 1++ denoted as Wc1. The inputs are the properties of the X(3872), including its mass and the ratio of its branching fractions of decays into J/ψρ0 and J/ψω. The predicted states are virtual state poles of the scattering matrix, pointing at a molecular nature of the X(3872) as well as its spin partners. They should show up as either a mild cusp or dip at the DD¯∗\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ D{\\overline{D}}^{\\ast } $$\\end{document} thresholds, explaining why they are elusive in experiments. The so far negative observation also indicates that the X(3872) is either a bound state with non-vanishing binding energy or a virtual state, only in these cases the X(3872) signal dominates over that from the Wc10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {W}_{c1}^0 $$\\end{document}. The pole positions are 3881.2−0.0+0.8\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {3881.2}_{-0.0}^{+0.8} $$\\end{document}−i1.6−0.9+0.7\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ i{1.6}_{-0.9}^{+0.7} $$\\end{document} MeV for Wc10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {W}_{c1}^0 $$\\end{document} on the fourth Riemann sheet of the D0D¯∗0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {D}^0{\\overline{D}}^{\\ast 0} $$\\end{document}-D+D∗− coupled-channel system, and 3866.9−7.7+4.6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {3866.9}_{-7.7}^{+4.6} $$\\end{document}− i(0.07 ± 0.01) MeV for Wc1±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {W}_{c1}^{\\pm } $$\\end{document} on the second Riemann sheet of the DD¯∗±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\left(D{\\overline{D}}^{\\ast}\\right)}^{\\pm } $$\\end{document} single-channel system. The findings imply that the peak in the J/ψπ+π− invariant mass distribution is not purely from the X(3872) but contains contributions from Wc10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {W}_{c1}^0 $$\\end{document} predicted here. The states should have isovector heavy quark spin partners with JPC = 0++, 2++ and 1+−, with the last one corresponding to Zc. We suggest to search for the charged 0++, 1++ and 2++ states in J/ψπ±π0.

How many vector charmoniumlike states lie in the mass range 4.2–4.35 GeV?

In recent years many vector charmonium(like) states were reported by different electron-positron collider experiments above 4.2 GeV. However, so far, there not only exists sizable tension in the parameters of those states, but there is also no consensus on the number of the vector states in this energy range. To some extend, this might be caused by the fact that the experimental data were typically analyzed in single channel analyses employing overlapping Breit-Wigner functions, in particular ignoring the effect of opening thresholds. In this study, we focus on the mass range between 4.2 GeV and 4.35 GeV, conducting a comprehensive analysis of eight different final states in e+e− annihilation. Our findings demonstrate that, within this mass range, a single vector charmoniumlike state, exhibiting properties consistent with a D1D¯ molecular structure and characterized by a pole location spoleY(4230)=(4227±4−i2(50−2+8)) MeV, can effectively describe all the collected data. This is made possible by allowing for an interference with the well-established vector charmonium ψ(4160) along with the inclusion of the D1D¯ threshold effect. Moreover, in contrast to experimental analyses, our study reveals that the highly asymmetric total cross sections for e+e−→J/ψππ and e+e−→J/ψKK¯ around 4230 MeV stem from the same physics, rooted in the approximate SU(3) flavor symmetry of QCD. Published by the American Physical Society 2024

E+e−→Λc+Λ¯c− Cross Sections and the Λc+ Electromagnetic Form Factors within the Extended Vector Meson Dominance Model

Within the extended vector meson dominance model, we investigate the e+e−→Λc+Λ¯c− reaction and the electromagnetic form factors of the charmed baryon Λc+ . The model parameters are determined by fitting them to the cross sections of the process e+e−→Λc+Λ¯c− and the magnetic form factor |G M| of Λc+ . By considering four charmonium-like states, called ψ(4500), ψ(4660), ψ(4790), and ψ(4900), we can well describe the current data on the e+e−→Λc+Λ¯c− reaction from the reaction threshold up to 4.96 GeV. In addition to the total cross sections and |G M|, the ratio |G E/G M| and the effective form factor |G eff| for Λc+ are also calculated, and found that these calculations are consistent with the experimental data. Within the fitted model parameters, we have also estimated the charge radius of the charmed Λc+ baryon.

Charmonium-like States at BESIII

Using e+e− annihilation data taken by the BESIII detector, several searches for charmonium-like states were performed: In e+e−→Ds*+Ds*− using datasets with center-of-mass energies of 4:23 GeV to 4:95 GeV corresponding to a total integrated luminosity of 15:67 fb−1, three peaks around 4:19 GeV, 4:41 GeV and 4:79 GeV were observed. In e+e− → D*0D*−π+ at 4:19 GeV to 4:95 GeV corresponding to Lint = 17:9 fb−1, three peaks at 4:20 GeV, 4:47 GeV and 4:67 GeV were identified. And in ψ(3770) → γηη′, γπ+π− J/ψ with Lint = 2:93 fb−1 an upper limit on the production of a scalar partner of the χc1(3872) was determined.

Search for the Y(2175) in photoproduction at GlueX

Abstract. The Y(2175), recently renamed to ϕ(2170), is one of the rare exotic candidates connected to strangeonium as compared to the heavier charmonium-like and bottomonium-like exotic states. Originally observed in initial state radiation events by the BaBar experiment in 2006, it is suggested to be a strange partner state of the charmonium-like exotic vector state Y(4230) that was one of the first of the so-called XYZ states reported in the charmonium mass region. The Y(2175) has been seen in various experiments and decay channels,but it has not yet been searched for in a photo-production experiment. In this talk we report on a measurement of the production cross section of the reaction γ + p → ϕπ+ π− + p based on data recorded by the GlueX experiment in order to search for Y(2175) → ϕπ+π−.>

Measurement of e+e−→pK−Λ¯+c.c.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {e}^{+}{e}^{-}\ o p{K}^{-}\\overline{\\Lambda}+c.c. $$\\end{document} cross sections between 4.009 GeV and 4.951 GeV

Using e+e− collision datasets corresponding to a total integrated luminosity of 21.7 fb−1 collected with the BESIII detector at the BEPCII collider at center-of-mass energies ranging from 4.009 GeV to 4.951 GeV, the energy-dependent cross sections of e+e−→pK−Λ¯+c.c.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {e}^{+}{e}^{-}\ o p{K}^{-}\\overline{\\Lambda}+c.c. $$\\end{document} are measured for the first time. By fitting these energy-dependent cross sections, we search for the excited ψ states ψ(4160) and ψ(4415), and the vector charmonium-like states ψ(4230), ψ(4360), and ψ(4660). No evidence for these is observed and the upper limits on the branching fractions of these states decaying into pK−Λ¯+c.c.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ p{K}^{-}\\overline{\\Lambda}+c.c. $$\\end{document} are set at the 90% confidence level.

Mass-spectra of light-heavy tetraquarks

The mass spectra of light-heavy tetraquarks [Formula: see text] ([Formula: see text]) are computed in a nonrelativistic diquark model with one-gluon exchange plus confining potential. In the diquark model, a [Formula: see text] state is regarded to be made of a light-heavy diquark ([Formula: see text]) and an antidiquark [Formula: see text] in antitriplet and triplet color configuration, respectively. The masses of charm mesons were calculated in order to fit the model parameters used to create the masses of tetraquarks and therefore enhance the model’s reliability. The masses of [Formula: see text] tetra-quark states are determined to be in the range of 3.8–4.7[Formula: see text]GeV, which is consistent with the experimentally reported charmonium-like states. In particular, the [Formula: see text], [Formula: see text] and [Formula: see text] tetraquarks, which have been seen experimentally, may all be described by our model.

Status and Prospects of Exotic Hadrons at Belle II

In the past 20 years, many new hadrons that are difficult to explain within the conventional quark model have been discovered in the quarkonium region; these are called exotic hadrons. The Belle II experiment, as the next-generation B factory, provides a good platform for exploring them. The charmonium-like states can be produced at Belle II in several ways, such as B meson decays, initial-state radiation processes, two-photon collisions and double charmonium production. Bottomonium-like states can be produced directly in e + e − colliding energies at Belle II with low continuum backgrounds. Belle II plans to perform a high-statistics energy scan from the threshold up to the highest possible energy of 11.24 GeV to search for new Yb states with J PC = 1−−, Xb [the bottom counterpart of χ c1(3872), also known as X(3872)] and partners of Zb states. We give a mini-review on the status and prospects of exotic hadrons at Belle II.

Strong decays of the charmonium-like state $Y(4230)$ and radiative transitions of low-lying charmoniums

В рамках ковариантной кварковой модели с использованием концепции аналитического конфайнмента изучаются сильные распады подобного чармонию состояния $Y(4230)$, полученного коллаборацией BESIII, а также доминирующие радиационные переходы низколежащих возбужденных состояний чармония. Резонанс $Y(4230)$ интерпретируется как четырехкварковое состояние молекулярного типа. Чтобы исключить все конституентные степени свободы из пространства физических состояний и точно зафиксировать перенормированные константы связи адронных состояний, используется условие композитности. Для расчете калибровочно-инвариантных амплитуд переходов в рассматриваемых процессах применяются спиральные амплитуды (лоренцевы структуры). Вычислены парциальная ширина сильного распада $Y\to J/\psi+f_0(980)$ и отношение $\mathcal B(Y {\to} K^{+}K^{-}J/\psi)/\mathcal B(Y\to\pi^{+}\pi^{-}J/\psi)$ коэффициентов ветвления сильных распадов (через резонанс $f_0(980)$) на частицы со скрытыми очарованиями, как те, что наблюдались коллаборацией BESIII в 2002 г. Для описания распределения кварков внутри адрона вводится единственный настроечный параметр состояний чармония $\eta_c( ^1S_0)$, $J/\psi( ^3S_1)$, $\chi_{c0}( ^3P_0 )$, $\chi_{c1}( ^3P_1)$, $h_c( ^1P_1)$ и $\chi_{c2}( ^3P_{2})$. Рассчитаны парциальные ширины однофотонных радиационных распадов для состояний $J/\psi( ^3S_1)$, $\chi_{cJ}( ^3P_{J})$ с $J=\{0, 1,2\}$ и $h_c( ^1P_1)$. Полученные оценки ширин распада находятся в разумном согласии с последними экспериментальными данными.

Strong decays of the charmonium-like state $$Y(4230)$$ and radiative transitions of low-lying charmoniums

Strong decays of the charmonium-like state $$Y(4230)$$ and radiative transitions of low-lying charmoniums

Light meson emissions of selected charmonium-like states within compact tetraquark configurations* *Supported by the National Natural Science Foundation of China (11705056, 12175037, 11947224, 11475192, 11975245, U1832173), the Key Project of Hunan Provincial Education Department under (21A0039), the State Scholarship Fund of China Scholarship Council (22006725011), the Sino-German CRC 110 “Symmetries and the Emergence of Structure in QCD” project by NSFC

We adopt the quark pair creation model to investigate the light meson emissions of several charmonium-like states. The quark pair creation model is applied to four-body systems, and we calculate the pion/kaon emissions of , , , , , and within compact tetraquark configurations. We find that the pion/kaon decay widths of and are relatively small, whereas the partial decay widths of the resonances , , , and are significant. We expect that our exploration of these decay behaviors will provide useful information for future experimental searches and theoretical interpretations.

χc1(2p): an overshadowed charmoniumlike resonance

A thorough study of the JPC = 1++ elastic {D}^0{overline{D}}^{ast 0} and D+D∗− scattering, where the form of the meson-meson interaction is inferred from lattice QCD calculations of string breaking, is carried out for center-of-mass energies up to 4 GeV. We show that the presence of χc1(3872), which can be naturally assigned to either a bound or virtual charmoniumlike state close below the {D}^0{overline{D}}^{ast 0} threshold, can overshadow a quasiconventional charmoniumlike resonance lying above threshold. This makes difficult the experimental detection of this resonance through the {D}^0{overline{D}}^{ast 0} and D+D∗− channels, despite being its expected main decay modes. We analyze alternative strong and electromagnetic decay modes. Comparison with existing data shows that this resonance may have already been observed through its decay to ωJ/ψ.

Do near-threshold molecular states mix with neighboring Q¯Q states?

The last two decades are marked by a renaissance in hadronic spectroscopy caused by the arrival of vast experimental information on exotic states in the spectrum of charmonium and bottomonium. Most of such states have properties at odds with the predictions of the quark model and reside very close to strong hadronic thresholds. Prominent examples are provided by the glorious $X(3872)$ charmonium-like state and the doubly charmed tetraquark $T_{cc}^+$ with the masses within less than 1 MeV from the $D\bar{D}^*$ and $DD^*$ open-charm thresholds, respectively. The universality of this feature hints towards the existence of a general pattern for such exotic states. In this work we discuss a possible generic mechanism for the formation of near-threshold molecular states as a result of the strong coupling of compact quark states with a hadronic continuum channel. The compact states that survive the strong coupling limit decouple from the continuum channel and therefore also from the formed hadronic molecule - if realised this scenario would provide a justification to treat hadronic molecules isolated, ignoring the possible influence from surrounding, compact quark-model states. We confront the phenomenology of the $D_{s1}(2460)$ and $D_{s1}(2536)$ with this picture and find consistency, although other explanations remain possible for those states.

Connection between near the Ds+Ds− threshold enhancement in B+→Ds+Ds−K+ and conventional charmonium χc0(2P)

Focusing on recent measurement of $B^+ \to D_s^+D_s^-K^+$ process given by the LHCb Collaboration, we propose that this newly observed near the $D_s^+D_s^-$ threshold enhancement can be due to the contribution of the $\chi_{c0}(2P)$, which is a $P$-wave charmonium below the $D_s^+D_s^-$ threshold. By performing a combined fit to the measured $D_s^+D_s^-$, $D_s^+K^+$, and $D_s^-K^+$ invariant mass spectra, introducing the $\chi_{c0}(2P)$ can well reproduce the near threshold enhancement in the $D_s^+D_s^-$ invariant mass spectrum. When depicting the whole $D_s^+D_s^-$ invariant mass spectrum, the contributions from higher charmonium $\psi(4230)$ and charmoniumlike state $X_0(4140)$ are obvious. In addition, a charmed meson $D^*(3^3S_1)$ with mass around 3015 MeV is found to be important to depict the $D_s^-K^+$ invariant mass spectrum well. Especially, the importance of node effect of the spatial wave function of the $\chi_{c0}(2P)$ is revealed, by which the anomaly of the ratio $\Gamma(X\to D^+D^-)/\Gamma(X\to D_s^+D_s^-)$ indicated by LHCb can be explained well. Finally, our scenario of the newly observed enhancement structure resulted from the $\chi_{c0}(2P)$ is enforced.

Improved description of the e+e−→pp¯π0 cross section line shape and more stringent constraints on ψ(3770) and ψ(4230)→pp¯π0

By using the cross sections of e^+e^- \to p\bar{p}{\pi}^0 measured at the center-of-mass energies from 3.65 to 4.60 GeV, we find that the line shape well agrees with pure continuum production parametrized by a power law function and the significance of both {\psi}(3770) and {\psi}(4230) \to p\bar{p}{\pi}^0 is less than 0.4{\sigma}. We set more stringent constraints on the charmless decays of the charmonium state, {\psi}(3770), and the charmoniumlike state, {\psi}(4230), to p\bar{p}{\pi}^0 than in previous measurements. The data are also used to estimate the cross sections of p\bar{p} \to {\pi}^0{\psi}(3770) and p\bar{p} \to {\pi}^0{\psi}(4230) that are essential for planning the data taking of the PANDA experiment.

Observation of Resonance Structures in e^{+}e^{-}→π^{+}π^{-}ψ_{2}(3823) and Mass Measurement of ψ_{2}(3823).

Using a data sample corresponding to an integrated luminosity of 11.3 fb^{-1} collected at center-of-mass energies from 4.23 to 4.70GeV with the BESIII detector, we measure the product of the e^{+}e^{-}→π^{+}π^{-}ψ_{2}(3823) cross section and the branching fraction B[ψ_{2}(3823)→γχ_{c1}]. For the first time, resonance structure is observed in the cross section line shape of e^{+}e^{-}→π^{+}π^{-}ψ_{2}(3823) with significances exceeding 5σ. A fit to data with two coherent Breit-Wigner resonances modeling the sqrt[s]-dependent cross section yields M(R_{1})=4406.9±17.2±4.5 MeV/c^{2}, Γ(R_{1})=128.1±37.2±2.3 MeV, and M(R_{2})=4647.9±8.6±0.8 MeV/c^{2}, Γ(R_{2})=33.1±18.6±4.1 MeV. Though weakly disfavored by the data, a single resonance with M(R)=4417.5±26.2±3.5 MeV/c^{2}, Γ(R)=245±48±13 MeV is also possible to interpret data. This observation deepens our understanding of the nature of the vector charmoniumlike states. The mass of the ψ_{2}(3823) state is measured as (3823.12±0.43±0.13) MeV/c^{2}, which is the most precise measurement to date.

Prediction of a Narrow Exotic Hadronic State with Quantum Numbers J^{PC}=0^{--}.

Lots of charmonium-like structures have been observed in the last two decades. Most of them have quantum numbers that can be formed by a pair of charm and anticharm quarks, thus it is difficult to unambiguously identify the exotic ones among them. In this Letter, by exploiting heavy quark spin symmetry, we present a robust prediction of the hadronic molecular scenario, where the ψ(4230), ψ(4360) and ψ(4415) are identified as DD[over ¯]_{1}, D^{*}D[over ¯]_{1}, and D^{*}D[over ¯]_{2}^{*} bound states, respectively. We show that a flavor-neutral charmonium-like exotic state with quantum numbers J^{PC}=0^{--}, denoted as ψ_{0}(4360), should exist as a D^{*}D[over ¯]_{1} bound state. The mass and width of the ψ_{0}(4360) are predicted to be (4366±18) MeV and less than 10MeV, respectively. The ψ_{0}(4360) is significant in two folds: no 0^{--} hadron has been observed so far, and a study of this state will enlighten the understanding of the mysterious vector mesons between 4.2 and 4.5GeV, as well as the nature of previously observed exotic Z_{c} and P_{c} states. We propose that such an exotic state can be searched for in e^{+}e^{-}→ηψ_{0}(4360) and uniquely identified by measuring the angular distribution of the outgoing η meson.