The cross sections for e+e- to pi+pi-J/psi, pi+pi-psi(2S), K+K-J/psi, DDbar, DDbar pi, D*Dbar, and D*D*bar are measured using data sample collected on or near the Upsilon(4S) resonance with the Belle detector at KEKB. A peak near 4.25 GeV/c^2, corresponding to the so called Y(4260), is observed in pi+pi-J/psi final state. In addition, there is another cluster of events at around 4.05 GeV/c^2. Two resonant structures are observed in the pi+pi-psi(2S) invariant mass distribution, one at 4361+-9+-9 MeV/c^2 with a width of 74+-15+-10 MeV/c^2, and another at 4664+-11+-5 MeV/c^2 with a width of 48+-15+-3 MeV/c^2. The rich structures observed in all these final states indicate that our understanding of the vector charmonium states above the open charm threshold is still poor, let alone the other possible dynamics such as charmonium hybrids or final state re-scattering and so on.
New results of the Belle experiment at the KEKB asymmetric e^+e^- collider are presented, in particular (a) measurement of the mass and width of the $η_c$ and $η_c'$ in B meson decays, (b) measurement of the mass, width and quantum numbers of the X(3872) and (c) observation of the $χ_{c2}$ in $B$ meson decays.
Belle and BaBar experiments at the KEKB and PEP-II B-factories provide also an excellent environment for spectroscopy studies. In this report we present recent results in the field of charmonium spectroscopy, focusing on new charmonium-like states observed in B decays, and on $J^{PC}=1^{--}$ resonances created in $e^+ e^-$ annihilation through the photon radiative return.
BaBar and Belle have recently revived the interest in charmonium spectroscopy, discovering many unexpected resonances. In this review, I'll focus mostly on the states found in B decays and double $\ccbar$. A better understanding of their production mechanism can help to discriminate among models, confirm tentative $J^{PC}$ assignments, and clarify the overall picture.
The recent results on charmonium and charmoniumlike states from Belle experiment are reviewed. We summarise searches in $B$ decays for possible $X$-like states in final states containing $η_c$. The new measurement of $e^+e^-\toπ^+π^-ψ(2S)$ improves the determination of the properties of $Y(4360)$ and $Y(4660)$. The fits including $Y(4260)$ are performed. Evidence for a charged charmoniumlike structure at $4.05~{\rm GeV}/c^2$ is observed in the $π^{\pm}ψ(2S)$ intermediate state in the $Y(4360)$ decays. Belle also updates the measurement on $e^+e^-\to KKJ/ψ$ via initial state radiation using the…
A brief review of experimental results on charmonium and charmonium-like hadron spectroscopy at B-factories is presented. A special focus is put on recent results of eta_c and eta_c(2S) study, X(3872) radiative decays, omega J/psi final state study and search for charmonium production in radiative Upsilon decays.
We report BELLE measurements of the exclusive cross sections for the processes e+e-->DD*, e+e-->DD, e+e-->DDpi, the first observation of psi(4415)-> DD*2(2460)bar decay and new state, Y(4660), using ISR. In addition, another cluster of events at around 4.05GeV/c2 is reported.
The review on experimental results on charmonium and charmonium-like spectroscopy from B-factories is presented. Main theoretical interpretations, such as conventional charmonium, molecular state, hybrids, tetraquarks and others are discussed.
We report a new analysis of double charmonium production in e+ e- annihilation using a data sample collected by the Belle experiment. We confirm our previous observation of the processes e+ e- -> J/psi eta_c (chi_c0, eta_c(2S)) and perform an angular analysis for these processes. Processes of the type e+ e- -> psi(2S) (c cbar)_resonant are observed for the first time. We also observe a new charmonium state - X(3940), produced in the process e+ e- -> J/psi X(3940).
We present the study of CP violation in charm and charmonium decays, using a data sample corresponding to 657 \times 10^6 BBbar events collected with the Belle detector at the Υ(4S) resonance at the KEKB asymmetric-energy e^+e^- collider. We report measurements of the polarization fraction and time-dependent CP-violation parameters of the decay B^0\to D^{*+}D^{*-} and of the branching fraction and charge asymmetry in the decay of the Cabibbo- and color-suppressed process B^{\pm} \to ψ(2S) π^{\pm}.
We report measurements of the branching fractions for the decays B->D_s1(2536)+ anti-D(*), where anti-D(*) is anti-D0, D- or D*-, and study of B->X(3872) K with X(3872) decaying to D*0 anti-D0 using a sample of 657 million B anti-B pairs recorded at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider.
Spectroscopy results for Belle and BaBar are reported. A particular focus is put on new results of the X(3872) state with its radiative decays to $J$/$ψ$$γ$ and $ψ'$$γ$, its decay into $J$/$ψ$3$π$ and the search for production in radiative Upsilon decays. Another focus is $L$=2 mesons, in particlar a possible $D$-wave assignment to the X(3872) and the confirmation of an Upsilon $D$-wave state.
We report recent results on the charmonium and charmoniumlike states based on a large data sample recorded at the $Υ(4S)$ and $Υ(5S)$ resonances with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider.
We confront predictions for hybrid charmonium and other gluonic excitations in the charm region with recently observed structures in the mass range above 3 GeV. The Y(4260), if resonant, is found to agree with expectations for hybrid charmonium. The possibility that other gluonic excitations may be influencing the data in this region is discussed.
The Belle II experiment at the SuperKEKB energy-asymmetric $e^+e^-$ collider is an upgrade of the B factory facility at KEK in Tsukuba, Japan. The experiment began operation in 2019 and aims to record a factor of 50 times more data than its predecessor. Belle II is uniquely capable of studying the so-called "XYZ" particles: heavy exotic hadrons consisting of more than three quarks. First discovered by Belle, these now number in the dozens, and represent the emergence of a new category within quantum chromodynamics. We present recent results obtained from Belle II data, and the future prospects…
It is shown that newly performed experimental studies by the Belle Collaboration are excellently incorporated in the unified picture for hadron spectra developed early. From our analysis it follows that the measured values for the masses of the BELLE states exactly coincide with the calculated masses of the states living in the corresponding KK towers.
We report on a search for new resonant states in the process gamma gamma --> D Dbar. A candidate C-even charmonium state is observed in the vicinity of 3.93 GeV/c^2. The production rate and the angular distribution in the gamma gamma center-of-mass frame suggest that this state is the previously unobserved chi'_(c2), the 2^3P_2 charmonium state.
Recent results in the field of spectroscopy from the BABAR experiment are reported, with particular attention to the new states observed in ISR and $γγ$ interactions using the full BABAR data sample. We confirm the states Y(4260) and Y(4360) with higher precision and for the first time the state Y(4660) is observed. We do not confirm the Y(4008) state reported by Belle. In addition, the analysis of the invariant mass of the $J/ψω$ system produced in $γγ$ interactions is presented in confirmation of the Belle observation of the X(3915) in this process.
We review recent results on charmonium-like exotic states from the Belle experiment. The two-photon process $γγ\to ϕ\jpsi$ is measured to search for Y(4140). No signal for the $Y(4140) \to ϕ\jpsi$ is observed. But a narrow peak with a significance of 3.2$σ$ deviations including systematic uncertainty is observed at 4350.6 MeV/$c^2$ that we named X(4350). We also search for charmonium-like states, including X(3872), Y(4140), X(3915) and X(4350), in $Υ(1S)$ and $Υ(2S)$ radiative decays. No significant signal of any charmonium-like state is observed. The processes $γγ\to VV$ ($V=ω$ or $ϕ$) are al…
We report on a search for the production of new resonance states in the process gamma gamma-->D Dbar. A candidate C-even charmonium state is observed in the vicinity of 3.93 GeV/c^2. The production rate and the angular distribution in the gamma gamma center-of-mass frame suggest that this state is the previously unobserved chi_{c2}', the 2 ^3P_2 charmonium state.
We review recent measurements of pure neutral final state production, gamma gamma to pi0 pi0 and eta pi0, and observations of new charmoniumlike resonances, X(3915) and X(4350), in the two-photon processes at the Belle experiment.
We report recent results on the properties of the X(3872) produced via the B-->KX(3872) decay process in the Belle detector. We compare these properties with expectations for possible charmonium-state assignments.
Charmonium spectroscopy gained renewed interest after the discovery in 2003 of the unpredicted X(3872) charmonium-like state, above the $D\overline{D}$ threshold. To date many charmonium-like states above the $D\overline{D}$ threshold have been claimed. Some of these states do not easily fit the conventional charmonium picture. In this article we review recent experimental results in this field, reported by the BaBar and Belle Collaborations.
Several charmonium-like states above $D\bar{D}$ threshold have been discovered at the Belle and BABAR B-factories. Some of these states are produced via Initial State Radiation (e.g. Y(4260) and Y(4350)), and some are observed in B-meson decays (e.g. X(3872), and Y(3940)). The Belle observations of the enhancements in the $ψ(2S)π^-$ and $χ_{c1}π^-$, i.e. the Z(4430)-, Z_1(4050)-, and Z_2(4250)-, have generated a great deal of interest, because such states must have minimum quark content $(c\bar{c}d\bar{u})$, i.e. these are candidate four-quark state. The BABAR Collaboration does not confirm th…
The last few years have witnessed a renaissance in the spectroscopy of heavy quarks. Several long elusive states have now been firmly identified, and several unexpected states have been reported by the high luminosity experiments at Belle, Babar, CLEO, and Fermilab. These discoveries have posed important theoretical questions for our understanding of QCD, and a variety of theoretical models have been proposed. These developments are critically discussed.
This talk reviews an unrepresentative selection of Belle's open-charm and charmonium analyses, focussing on new developments and topics of interest to the DIS community. Highlights include an X(3872) analysis favoring J^PC = 1++, and the D0-D*0bar bound-state interpretation.
We review recent charmonium and bottomonium spectroscopy results from the B-factories Belle and \babar. A particular focus is given to the new $η_{c}(1S)$ and $η_{c}(2S)$ measurement and to the radiative transitions from $Υ(2S)$ and $Υ(3S)$ with converted photons.
One of the most intriguing puzzles in hadron spectroscopy are the numerous charmonium-like states observed in the last decade, including charged states that are manifestly exotic. The $BABAR$ and Belle experiments have extensively studied those in B meson decays, initial state radiation processes and two photon reactions. We can question what we have understood after 11 year search in this field, and try to combine results to conclude on what these new unpredicted resonant states are, and how they can be accommodated in the theory. Big effort has been made from theoretical and experimental poi…
We report branching fractions and charge asymmetries for exclusive decays of charged and neutral B mesons to two-body final states containing a charmonium meson, J/psi or psi(2S). This result is based on a 29.4 fb^{-1} data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric e+e- collider.
We report recent observations of baryonic B decays with charmless and charmed baryons in the final state. We show the angular distributions of the di-baryon low-mass enhancements in the charmless three-body baryonic B decays andthe branching fractions of B decays with two charmed baryons or charmonium in the final states. We also report the observation of the decay $η_c \to Λ\barΛ$ at Belle.
We present preliminary measurements of the cross sections for e+e- --> KS KL pi0 and KS KL pi0 pi0 obtained using the technique of Initial State Radiation with 469 fb^-1 of e+e- collision data collected with the BABAR detector at or near the Upsilon(4S) resonance. The resonant substructure of KS KL pi0 is investigated, and branching fractions for the decays of the charmonium resonances J/psi and psi(2S) into these final states are measured.
Since the discovery of the X(3872) in 2003 the B-factory experiments BaBar and Belle have been driving forces in the spectroscopy of new charmonium-like states. In this article the latest results on the decays X(3872) -> D0 D*0bar and X(3872) -> psi gamma, where psi stands for J/psi or psi(2S), are presented and analyses of Z(4430)+ -> psi pi+ and Z(4050/4250)+ -> chi_c1 pi+ are discussed.
In the quark model, hadrons are dominantly bound states of quark-antiquark pairs (mesons) or three quarks (baryons), but QCD also allows hadronic states to be composed of more quarks bound together. Recently, BESIII, Belle and LHCb have confirmed the existence of four-quark and pentaquark candidates. These new states, along with experimentally observed resonances that do not fit well into the charmonium and bottomonium spectra, present challenges and opportunities for strong interaction theory. In this talk, I will review results on charmonium-like exotic quark states that have been observed b…
We report the first observation of a new charmonium state at a mass of $(3.943 \pm 0.006 \pm 0.006) {GeV}/c^2$. This state, called X(3940), is observed in the process $e^+ e^- \to J/ψX(3940)$ in the spectrum of masses recoiling against a reconstructed $J/ψ$. We also observe the decay of the X(3940) into $D^* \bar{D}$ and measure the intrinsic width of this state to be less than $52 MeV/c^2$ at the 90% C.L. These results are obtained from a $350 fb^{-1}$ data sample collected with the Belle detector near the $Υ(4S)$ resonance, at the KEKB asymmetric energy $e^+ e^-$ collider.
We present a study of Y(4260) properties using the initial-state radiation process e^+e^- -> gamma_{ISR} Y(4260). The Y(4260) resonance is reconstructed in the pi^+ pi^- J/ψdecay mode, using data collected by the Belle detector at the KEKB e^+e^- collider. We find a significant signal with a central mass value of (4295 +-10 +10 -3) MeV/c^2 and a width of (133 +-26 +13 -6) MeV/c^2. We find Gamma_{ee}.B(Y(4260) -> pi^+ pi^- J/ψ) = (8.7 +- 1.1 +0.3 -0.9) eV. These results are preliminary.
Inspired by the similarity of mass gaps of $J/ψ$ and $Υ$ families, the prediction of missing higher charmonium with mass $4263$ MeV and very narrow width is made. In addition, the properties of two charmonium-like states, $X(3940)$ and $X(4160)$, and charmonium $ψ(4415)$ are discussed. Here, $X(3940)$ as $η_c(3S)$ is established while the explanation of $X(4160)$ to be $η_c(4S)$ is fully excluded and $η_c(4S)$ is typically a very narrow state. These predictions can be accessible at BESIII, Belle and BelleII in near future.
We report the observation of a narrow charmonium-like state produced in the exclusive decay process B+ -> K+ pi+pi- J/psi. This state, which decays into pi+pi- J/psi, has a mass of 3872.0+-0.6(stat)+-0.5(syst) MeV, a value that is very near the M_D + M_D* mass threshold. The results are based on an analysis of 152M B-Bbar events collected at the Upsilon(4S) resonance in the Belle detector at the KEKB collider. The statistical significance of the signal is in excess of 10 sigma.
Motivated by very recent measurement of the radiative decays of $Υ(1S)$ to $χ_{c1}$ at Belle, we use the nonrelativistic QCD factorization theory and calculate the branching fractions of the radiative decays of bottomonium into S-wave and P-wave charmonium, i.e. $Υ(nS) \to η_c(nS)+γ$ and $Υ(nS)\to χ_{cJ}+γ$. We systematically studied the branching fractions of the radiative decays of bottomonium into charmonium. Compared to the previous calculation, we obtained the analytical expression for the decay widths and considered the color-octet contributions. For $Υ(nS) \to η_c(nS)+γ$, the relativist…
We report recent results on the properties of the X(3872) produced via the B+ --> K+ X(3872) decay process. We observe X -->pi+pi-pi0 J/psi decays where the 3pi invariant masses cluster near the upper kinematic boundary suggesting that they originate from sub-threshold decays to virtual omega(782) mesons. This is consistent with expectations for a DD*-bar bound state interpretation for the X(3872). In addition, we constrain the possible charmonium-state assignments for this particles. Results are obtained from a 253/fb data sample that contains 274 million BB-barr pairs that was collected near…
We report the first observation of a narrow charmmonium state produced in the exclusive decay process B+->K+ pi+pi- J/psi. This state, which decays into pi+pi-J/psi, has a mass of 3871.8+-0.7(stat)+-0.4(syst) MeV, which is very near the M_D + M_D* mass threshold. The results are based on an analysis of 152M BBbar events collected at the Upsilon(4S) resonance in the Belle detector at the KEKB collider.
The large data sample accumulated by the Belle experiment at KEKB asymmetric energy $e^+ e^-$ collider provides opportunities to study charmonia (bottomonia) and charmonium-like (bottomonium-like) exotic particles. In this review, we report recent results on these topics from Belle, including searches for $B\to h_c K$, $B\to Y(4260)K$, $B\to X(3872/3915) (\to χ_{c1} π^0 ) K$, $B^0 \to X(3872) γ$, $e^+e^- \to γχ_{cJ}$ and a new measurement of the $e^+ e^-\to Υ(nS) π^+ π^- (n=1,2,3)$ cross sections at energies from 10.52 to 11.02 GeV.
$K^0_SK^0_S$ production in two-photon collisions has been studied using a 397.6 fb$^{-1}$ data sample collected with the Belle detector at the KEKB $e^+e^-$ collider. For the first time the cross sections are measured in the two-photon center-of-mass energy range between 2.4 GeV and 4.0 GeV and angular range $|\cosθ^*|<0.6$. Combining the results with measurements of $γγ\to K^+K^-$ from Belle, we observe that the cross section ratio $σ(K^0_SK^0_S)/σ(K^+K^-)$ decreases from ~0.13 to ~0.01 with increasing energy. Signals for the $χ_{c0}$ and $χ_{c2}$ charmonium states are also observed.
We present a new analysis of double charmonium production in e^+ e^- annihilation. The observation of the processes e^+ e^- -> J/psi eta_c, J/psi chi_c0, and J/psi eta_c(2S) is confirmed using a dataset more than three times larger than that of Belle's previous report, and no evidence for the process e^+ e^- -> J/psi J/psi is found. We perform an angular analysis for J/psi eta_c production and set an upper limit on the production of J/psi J/psi. Processes of the type e^+ e^- -> psi(2S) (cc)_res have been observed for the first time; their rates are found to be comparable to those of e^+ e^- ->…
In spite of the fact that the two-body $B$ decays into $χ_{c2}$ such as $B \to χ_{c2} K^{(*)}$ are suppressed by the QCD factorization effect, the inclusive $B \to χ_{c2} X$ branching fraction amounts to one third of the non-suppressed $B \to χ_{c1} X$ decays because of the decay modes to the multi-body final states. Using a large statistics $Υ(4S)$ data sample corresponding to 772 million $B$ meson pairs accumulated by the Belle detector at the KEKB $e^+e^-$ collider, precise measurements of inclusive $B \to χ_{c1}$ and $χ_{c2}$ branching fractions are carried out. The multi-body final states…
Using samples of 102 million $Υ(1S)$ and 158 million $Υ(2S)$ event samples collected with the Belle detector, we report on the first search for charge-parity-even charmonium and charmonium-like states in $Υ(1S)$ and $Υ(2S)$ radiative decays. No significant $χ_{cJ}$ or $η_c$ signal is observed and 90% C.L. limits on $\BR(Υ(nS)\to γχ_{cJ})$ ($n=1,2$ and $J=1,2,3$) are obtained. No significant signal of any charmonium-like state is observed. The product branching fraction limits $\BR(Υ(nS)\to γX(3872))$ $\BR(X(3872)\toπ^+π^-\jpsi)$, $\BR(Υ(nS)\to γX(3872))$ $\BR(X(3872)\toπ^+π^-π^0 \jpsi)$, $\BR(…
Using a sample of 158 million Υ(2S) events collected with the Belle detector, charmonium and charmonium-like states with even charge parity are searched for in Υ(2S) radiative decays. No significant χ_{cJ} or η_c signal is observed and the following upper limits at 90% confidence level (C.L.) are obtained: BR(Υ(2S)\to γχ_{c0})< 1.0 \times 10^{-4}, BR(Υ(2S) \to γχ_{c1})<3.6 \times 10^{-6}, BR(Υ(2S) \to γχ_{c2})<1.5 \times 10^{-5}, and BR(Υ(2S) \to γη_c)< 2.7 \times 10^{-5}. No significant signal of any charmonium-like state is observed, and we obtain the limits \BR(Υ(2S)\to γX(3872))\times\BR(X…
We present a study of the X(3940) state in the process e+e- -> J/psi D* Dbar. The X(3940) mass and width are measured to be (3942 +7 -6 +- 6)MeV/c^2 and Gamma=(37 + 26 - 15 +- 8 MeV. In the process e+e- -> J/psi D* D*bar we have observed another charmonium-like state, which we denote as X(4160), in the spectrum of invariant masses of D*+ D*- combinations. The X(4160) parameters are M= 4156 + 25 - 20 +- 15 MeV/c^2 and Gamma = 139 + 111 -61 +- 21 MeV. The analysis is based on a data sample with an integrated luminosity of 693 /fb recorded near the Upsilon(4S) resonance with the Belle detector at…
Initial State Radiation (ISR) effect is implemented in Madgraph using photon structure functions. Detailed examinations are performed against other generators including Whizard, BabayagaNLO and KKMC, for various physics processes at linear colliders such as 240GeV CEPC and 10.58GeV Belle II. ISR effects on new physics searches are also discussed, taking anomalous gauge boson coupling and dark photon as examples. An ISR plugin is made public for wide usage.
We review selected recent Belle results in quarkonium physics, that include precision measurement of the eta_b(1S) parameters, evidence for the eta_b(2S); evidence for the psi_2(1D); observation of the psi(4040) and psi(4160) transitions to J/psi eta with anomalously high rates; observation of the Upsilon(5S) transitions to Upsilon(1D)pi+pi- and Upsilon(1S,2S)eta. The low excitations of charmonium and bottomonium are in agreement with the Lattice QCD and effective theories calculations, while high excitations show unexpected properties.
The hyperfine splitting for the 2S charmonium state is calculated and the predicted number is $Δ_{\rm HF}(2S) = 57 \pm 8$ MeV, being by derivation the lower bound of this splitting. It results in $M(η_c(2S))= 3630 \pm 8$ MeV, which is smaller by two standard deviations than found in the Belle experiment \cite{ref.01}, but close to the $η_c(2S)$ mass observed by the same group in the experiment $e^+e^- \to J/ψη_c$ \cite{ref.06} where $M(η_c(2S)) = 3622 \pm 12$ MeV was found.
A new charged state, called $Z_c(3900)$ has been recently observed by BESIII collaboration in $J/ψπ^{\pm}$ channel. The same has been confirmed by Belle (called Z(3894.5 in the Belle paper). In this short note we discuss probable interpretations of this charmonium like state which we call Z(3900).
We study the baryonic charmonium decays of B mesons, B+ to etac K+ and B+ to J/psi K+, where the etac and J/psi subsequently decay into a p pbar or Lambda Lambdabar pair. We measure the J/psi to p pbar, Lambda Lambdabar anisotropy parameters, alpha_B = -0.60 +- 0.13 +-0.14 (p pbar), -0.44 +- 0.51 +- 0.31 (Lambda Lambdabar) and compare to results from e+e- to J/psi formation experiments. We also report the first observation of etac to Lambda Lambdabar. The measured branching fraction is B(etac to Lambda Lambdabar) = (0.87 +0.24 -0.21(stat) +0.09 -0.14(syst) +- 0.27 (PDG)) x 10^-3. This study is…
It is shown that difficulties in reconciling the values of the cross section e+e- -> J/psi+eta_c measured at BELLE and calculated within non-relativistic QCD (NRQCD) are caused not by some misinterpretation of the data or other exotic explanations, but by poor applicability of NRQCD to such processes. We use general theory of hard exclusive processes in QCD together with more realistic models of charmonium wave functions, and show that the BELLE result can be naturally explained.
We investigate the $D\bar{D}$ production in $e^+e^-$ annihilations near threshold in an effective Lagrangian approach. This shows that the lineshape of the cross section near threshold is sensitive to the contributions from $ψ^\prime$, though it is below the $D\bar{D}$ threshold. The recent experimental data from the BES and Belle collaborations allow us to determine the $ψ^\prime D\bar{D}$ coupling constant which appears to be consistent with other theoretical studies. As a consequence, the $ψ^\prime$-$ψ(3770)$ mixing parameter can be extracted around the $ψ(3770)$ mass region. Resonance para…
We study the direct production of the $J^{PC}=1^{++}$ charmonium state $χ_{c1}(1P)$ in electron-positron annihilation by carrying out an energy scan around the mass of the $χ_{c1}(1P)$. The data were collected with the BESIII detector at the BEPCII collider. An interference pattern between the signal process $e^+e^-\to χ_{c1}(1P) \to γJ/ψ\toγμ^+μ^-$ and the background processes $e^+e^-\to γ_{\mathrm{ISR}} J/ψ\toγ_{\rm{ISR}}μ^+μ^-$ and $e^+e^-\toγ_{\rm{ISR}}μ^+μ^-$ are observed by combining all the data samples. The $χ_{c1}(1P)$ signal is observed with a significance of 5.1$σ$. This is the firs…
Using $525$ pb$^{-1}$ data collected with the BESIII detector at $e^+e^-$ central-of-mass energy 4.26 GeV, the BESIII Collaboration observed a charged charmoniumlike state $Z_c(3900)\toπ^{\pm}J/ψ$ with mass $M[Z_c(3900)]=3899.0\pm 3.6 \pm 4.9$ MeV/c$^2$, and width $Γ[Z_c(3900)]=46\pm 10 \pm 20$ MeV. The significance of this state was estimated to be $>8σ$ in all kinds of systematic tests. Using $967$ fb$^{-1}$ data recorded by the Belle detector on or near $Υ(nS)$, n=1, 2, $\cdots$, 5 resonances, the $e^+e^- \to π^+π^-J/ψ$ process has been studied through initial-state-radiation (ISR) method. …
Recent experimental results on charmonium $h_c(^1P_1)$, $η_c(1S)$ and $η_c(2S)$ from Belle, BaBar, CLEO and BESIII are reviewed. $h_c$ production and properties, the $η_c(1S)$ lineshape and the observation of $η_c(2S)$ in $ψ'$ decays are discussed.
Using a sample of 102 million $Υ(1S)$ events collected with the Belle detector, we report on the first search for charge-parity-even charmonium and charmonium-like states in $Υ(1S)$ radiative decays. No significant $χ_{cJ}$ or $η_c$ signal is observed and 90% C.L. limits on $\BR(Υ(1S)\to γχ_{c0})<6.5 \times 10^{-4}$, $\BR(Υ(1S)\to γχ_{c1})<2.3\times 10^{-5}$, $\BR(Υ(1S)\to γχ_{c2})<7.6 \times 10^{-6}$, and $\BR(Υ(1S)\to γη_c)<5.7\times 10^{-5}$ are obtained. The product branching fraction limits $\BR(Υ(1S)\to γX(3872)) \BR(X(3872)\toπ^+π^-\jpsi)< 1.6 \times 10^{-6}$, $\BR(Υ(1S)\to γX(3872)) \B…
We propose the initial single chiral particle emission mechanism, with which the hidden-charm di-kaon decays of higher charmonia and charmonium-like states are studied. Calculating the distributions of differential decay width, we obtain the line shape of the $J/ψK^+$ invariant mass spectrum of $ψ_i\to J/ψK^+K^-$, where $ψ_i=ψ(4415), Y(4660)$, and $ψ(4790)$. Our numerical results show that there exist enhancement structures with both hidden-charm and open-strange decays, which are near the $D\bar{D}_s^*/D^*\bar{D}_s$ and $D^*\bar{D}_s^*/\bar{D}^*{D}_s^*$ thresholds. These charged charmonium-li…
