We apply the method of QCD sum rules to study the $q c \bar q \bar c$ tetraquark states with the exotic quantum number $J^{PC} = 3^{-+}$, and extract the mass of the lowest-lying state to be ${4.49^{+0.45}_{-0.41}}$ GeV. To construct the relevant tetraquark currents we need to explicitly add the covariant derivative operator. Our systematic analysis of these interpolating currents indicates that: a) this state readily decays into the $P$-wave $[ρJ/ψ] / [ωJ/ψ]$ channel but not into the $ [ρχ_{c2}]/[ωχ_{c2}]/[J/ψf_2(1270)]$ channels, and b) it readily decays into the $[D^* \bar D_2^*]$ channel but not into the $P$-wave $[D^* \bar D^*]$ channel.
The BESIII Experiment at the Beijing Electron Positron Collider (BEPCII) collected large data samples for electron-positron collisions with center-of-mass above 4 GeV. The analysis of these samples has resulted in a number of surprising discoveries, such as the discoveries of the electrically charged $\mathrm{Z_c}$ structures, which, if resonant, cannot be accommodated in the traditional charm quark and anti-charm quark picture of charmonium. In this talk, we will review the current status of the analyses of the exotic states, as well as a number of other interesting features in the new BESIII…
We review selected lattice results on the charmonium spectrum and first attempts to search for the existence of exotic states. The hadro-quarkonium model was proposed to interpret some of the exotic states as a quarkonium core inside a hadron. We present a lattice study of the hadro-quarkonium model in the limit of static quarks. The charm quark decouples in low energy observables and binding energies of charmonium. In a model calculation we are able to evaluate the corrections to decoupling of the charm quark in the continuum.
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…
Using the dynamical diquark model, we calculate the electric-dipole radiative decay widths to $X(3872)$ of the lightest negative-parity exotic candidates, including the four $I=0$, $J^{PC} \! = \! 1^{--}$ ("$Y$") states. The $O$(100--1000 keV) values obtained test the hypothesis of a common substructure shared by all of these states. We also calculate the magnetic-dipole radiative decay width for $Z_c(4020)^0 \! \to \! γX(3872)$, and find it to be rather smaller ($<$~10 keV) than its predicted value in molecular models.
The resonances, containing $c\bar c$ plus $s\bar s$ (or light $q\bar q$) quarks in the mass region $(3900-4700)$ MeV, are analyzed in the relativistic strong coupling theory, with and without channel coupling phenomena. The conventional charmonium spectrum is presented, being calculated with the relativistic string Hamiltonian, which does not contain fitting parameters, while for high excitations the universal flattened confining potential is used. It is shown that $X(4274),X(4500),X(4700)$ can be identified as $3\,^3P_1, 4\,^3P_0, 5\,^3P_0$ states. The exotic states are considered using the c…
Gluonic excitation of non-exotic hybrid charmonium from lattice QCD
利用猝灭格点量子色动力学研究了具有非奇异量子数$J^{PC}=0^{-+}$、$1^{--}$和$1^{++}$的杂化粲偶素${\bar c} c g$的基态和第一激发态.它们在文献中被完全忽略，只是因为它们的基态与$η_c$，$J/ψ$和$χ_{c1}$简并，并且在实验中很难与这些常规的粲素介子区分开来。然而，我们在第一激发态中观察到了强的胶子径向激发，我们预测它们的质量分别为4.352（225）GeV、4.379（149）GeV和7.315（257）GeV，与相应的常规粲偶素的第一激发态完全不同。它们与最近发现的Y（4260）态的相关性和未来对其他态的实验研究也进行了讨论。
I. Light Scalars as Four-quark States II. Isotensor Tensor Tensor E(1500-1600) State III. X(3872) State as Charmonium χ_{c1}(2P) IV. Two-gluon Annihilation of Charmonium χ_{c2}(2P) There are considered problems of the exotic states, in which the author with his collaborators has made clear physical predictions, considerable part of wich is supported by experement already
We study the photon spectrum in the radiative decays of the charmonium $\frac{1}Γ\frac{dΓ(J/ψ\rightarrowγgg)}{dz}$ as an excellent scene for hunting the exotic mesons (hybrids $q\bar{q}g$ and glueballs $gg$) and an ideal frame for the theoretical and phenomenological investigations of the gluon nature in IR, by subtle estimation of its non-zero effective mass which seems required in Quark-Gluon Constituent Model (QGCM) for identifying the nature of these exotic species.
Unitarity of exclusive quark combination model: Exotic hadron production, entropy change and charmonium production for colour-singlet many-quark system
禁闭表示一个渐近夸克态，除非它的能量为零，否则是不可观测的。幺正性表明夸克系统的一个确定态跃迁到任意末态的总概率恰好为1。这个演讲回顾了一些重要的结论/预测，如组合模型的酉性等基本性质，如标题所述。在后记部分我们也讨论了底夸克的能量损失。在会议的餐桌讨论中，作者结合大横动量J/Psi的抑制和大横动量下B衰变对J/Psi的贡献，提出了底夸克能量损失与轻夸克相当的期望，只要b夸克的横动量足够大于b夸克的质量。这是指在La Rencontre de l 'annee derniere中介绍的射流-介质相互作用的物理图像。
It is suggested that the recently reported charged charmoniumlike resonance $Z_c(4100)$ and the previously observed $Z_c(4200)$ are two states of hadrocharmonium, related by the charm quark spin symmetry in the same way as the lowest charmonium states $η_c$ and $J/ψ$. Namely, the $Z_c(4100)$ is (dominantly) the $η_c$ embedded in an light-quark excitation with quantum numbers of a pion, while the $Z_c(4200)$ is a similar four quark state containing $J/ψ$ instead of $η_c$. It is argued that this picture suggests certain relations between the properties of the two exotic resonances and a distinct…
Very recently LHCb reported the evidence of a new charged charmonium-like structure in the $J/ψπ^-$ invariant mass spectrum near 4600 MeV. In this work we investigate this structure together with three other charged charmonium-like states, the $Z_c(3900)$, $Z_c(4020)$, and $Z_c(4430)$. Our results suggest that the two higher states can be established as the first radial excitations of the two lower ones, all of which have the quantum numbers $J^{PC}=1^{+-}$. We propose to search for more relationship among exotic hadrons in order to better understand them.
Tsinghua University（清华大学）；Southeast University（东南大学）；Universität Bonn, Helmholtz-Institut für Strahlen- und Kernphysik（波恩大学，亥姆霍兹辐射与核物理研究所）；Instituto de Física Corpuscular (centro mixto CSIC-UV)（粒子物理研究所（CSIC-UV联合中心））；Fudan University（复旦大学）；School of Physics, Zhengzhou University（郑州大学物理学院）
本文综述了与 $b$ 夸克相关的奇特强子（如 $Z_b$、$X_b$、$Y_b$ 态）的实验和理论研究，强调了重底夸克在理论计算中的优势，并介绍了 Belle、Belle II 和 LHCb 实验的最新成果。
The recent results on Charmonium and Charmonium-like states at BESIII are reviewed, including the observation of $\rm Z_{cs}(3985)$ state, the study of the new decay modes of $ψ_2(3823)$ state, observation of resonance structure in $\rm e^+e^- \to π^+π^-ψ_2(3823)$ process, the study of the $\rm e^+e^- \to K^+K^-J/ψ$ process, cross section measurement of $\rm e^+e^- \to ωπ^0$ and $ωη$ process, branching fraction measurement of $ψ(3686)\to\barΣ^0Λ+ c.c.$ process. Decay channels for $χ_{cJ} \to Λ\barΛ$, $χ_{cJ} \to Λ\barΛη$, $ψ(3686) \to Λ\barΛω$ and $η_c(2S)\to3(π^+π^-)$ are also discussed. The …
Inspired by the first observation of a vector charmonium-like state $Y(4626)$ decaying to a meson pair $D_{s}^{+}D_{s1}(2536)^{-}$, which could be viewed as a $P$-wave scalar-scalar $[cs][\bar{c}\bar{s}]$ tetraquark state, we predict a potential vector charmonium-like state $Y$ with $P$-wave scalar-scalar $[cq][\bar{c}\bar{q}]$ configuration. The corresponding mass spectrum of $Y$ state is calculated to be $4.33^{+0.16}_{-0.23}~\mbox{GeV}$ in the framework of QCD sum rules. We suggest that the predicted $Y$ state could be looked for in an open-charm $e^{+}e^{-}\rightarrow\bar{D}D_{1}(2420)+c.c…
Exploring open-charm decay mode $Λ_c\barΛ_c$ of charmonium-like state $Y(4630)$
新观测到的$X, Y, Z$奇异态肯定不是标准的$Q\bar Q'$结构，因此它们的存在对我们对强子物理基本原理的理解构成了挑战。因此，对它们的衰变模式的研究必将对相关物理学的发展有所启发。一般来说，四夸克态可能是分子态、四夸克态或它们的混合态。在本工作中，我们采用了这样的假设：$Y(4630)$是由一个双夸克和一个反双夸克组成的类粲偶素四夸克态。如果这是真的，它的有利衰变模式应该是$Y(4630)$衰变成开魅重子对，因为这种跃迁是通过强相互作用发生的，并且是超OZI允许的。本文在夸克对产生模型的框架下计算了$Y(4630)\toΛ_c\barΛ_c$的衰变宽度。在一定的误差范围内，我们计算的四夸克组态的部分宽度的数值结果与Belle数据相吻合。
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 $D\bar D_1,D^*\bar D_1$ and $D^*\bar D^*_2$ bound states, respectively. We show that a flavor-neutral charmonium-like exotic state with quantum numbers $J^{PC}=0^{--}$,…
