XYZ mesons and Glueballs: effects of the quark-gluon mixing
Nikolai Kochelev
备注：
10 pages,8 figures, based on the talk given at Helmholtz - DIAS International Summer School "Quantum Field Theory at the Limits:from Strong Fields to Heavy Quarks", 18-30 July 2016, Dubna, Russia
We present the new developments in the physics of XYZ mesons and glueballs and discuss the connection between properties of the $XYZ$ mesons and glueballs, and the structure of the QCD vacuum. It is shown that the mixing between quark and gluon degree of freedoms induced by the nontrivial topological structure of the QCD vacuum might affect strongly the properties of the exotic hadrons. A new interpretation of the $XYZ$ mesons as the mixing between radial excitations of light quark-antiquark systems and states with heavy quark content is suggested. We introduce also a new mechanism of quarkonia production in hadron-hadron collisions coming from the mixing of light and heavy quark sectors of QCD. This mechanism is based on the nontrivial topological structure of the QCD vacuum and might explain the polarization puzzle in inclusive $J/Ψ$ production in high energy reactions. The possibility of big changes of the scalar and pseudoscalar glueball masses in the hot gluonic plasma is established and their consequences in the phase structure of QCD analyzed.
A Reply to "Comment on `Finding the $0^{--}$ Glueball' " [arXiv:1702.06634] and comment on `Is the exotic $0^{--}$ glueball a pure gluon state?' [arXiv:1611.08698]
We consider the dynamics of the scalar and pseudoscalar glueballs in the Quark-Gluon Plasma (QGP). By using the instanton model for the QCD vacuum we give the arguments that the nonperturbative gluon-gluon interaction is qualitatively different in the confinement and deconfinement phases. Based on this observation it is shown that above $T_c$ the values of the scalar and pseudoscalar glueball masses might be very small. The estimation of the temperature of scale invariance restoration, at which the scalar glueball becomes massless, is given. We also discuss the Bose-Einstein condensation of th…
We study the scalar, vector and tensor two-gluon and trigluon glueball spectra in the framework of 5-dimension dynamical holographic QCD model, where the metric structure is deformed self-consistently by the dilaton field. For comparison, the glueball spectra are also calculated in the hard-wall and soft-wall holographic QCD models. In order to distinguish glueballs with even and odd parities, we introduce the positive and negative coupling between the dilaton field and glueballs, and for higher spin glueballs, we introduce a deformed 5-dimension mass. With this set-up, there is only one free …
We present a new calculation of the mass and width of the exotic $0^{--}$ glueball in the framework of the QCD sum rules. We next construct a new current which couples to a pure $0^{--}$ gluon state and derive consistent and stable sum rules. A previously used current in this approach was shown to be inconsistent. We obtain for this state a mass $M_G=6.3^{+0.8}_{-1.1}$ GeV and an upper limit for the total width $Γ_G\leq 235$ MeV. These values can be used as an important guide for the experimental search of this exotic state. We argue that the mixing of this glueball state with $0^{--}$ tetraqu…
The Abelian decomposition of QCD which decomposes the gluons to the color neutral binding gluons and the colored valence gluons shows that QCD can be viewed as the restricted QCD (RCD) made of the binding gluons which has the valence gluons as colored source, and simplifies the QCD dynamics greatly. In particular, it tells that the gauge covariant valence gluons can be treated as the constituents of hadrons, and generalizes the quark model to the quark and valence gluon model. So it provides a comprehensive picture of glueballs and their mixing with quarkoniums, and predicts new hybrid hadrons…
Glueball as a bound state in the self-dual homogeneous gluon field
利用一个简单的标量场的相对论QFT模型，我们证明了解析禁闭（传播子是复$p^2$ -平面中的整函数）和弱耦合常数导致了两粒子束缚态的Regge行为。在QCD中，我们假设胶子真空是由自对偶的齐次经典场实现的，而齐次经典场是Yang-Mills方程的解。这个假设导致了夸克和胶子的分析禁闭。在单胶子交换近似下，我们从QCD生成泛函中提取出无色的$0^{++}$双胶子态。这个束缚态的质量由贝特-萨尔彼得方程定义。如果胶子凝聚体是$<(α_s/π) G G >=0.012~{\rm GeV}^4$，那么对于$α_s=0.33$，胶球质量是$1765~{\rm MeV}$。
Nonlocal gluon condensates are vacuum expectations of the product of gluon field strength tensors. Short-distance expansions of two-, three-, and four-gluon condensates are presented up to dimension-8 local operators. We propose a method for calculating the Wilson coefficients based on the presented expansions and the Feynman diagram technique in the background field approach. The method is demonstrated using the glueball current correlators as examples. Methodological aspects of the background field approach are discussed in relation to glueball studies within QCD sum rules. We confirm the re…
The Abelian decomposition of QCD which decomposes the gluons to the color neutral binding gluons (the neurons) and the colored valence gluons (the chromons) gauge independently naturally generalizes the quark model to the quark and chromon model which could play the central role in hadron spectroscopy. We discuss the color reflection symmetry, the fundamental symmetry of the quark and chromon model, and explain how it describes the glueballs and the glueball-quarkonium mixing in QCD. We present the numerical analysis of glueball-quarkonium mixing in $0^{++}$, $2^{++}$, and $0^{-+}$ sectors bel…
Based on correction from instanton-gluon interference to correlation function, the properties of the $0^{-+}$ pseudoscalar glueball is investigated in a family of finite-width Gaussian sum rules. In the framework of semiclassical expansion for quantum chromodynamics $(\textrm{QCD})$ in the instanton liquid background, the contribution arising from the the interference between instantons and the quantum gluon fields is calculated, and included in the correlation function together with pure-classical contribution from instantons and the perturbative one. The interference contribution is turned t…
Comment on `Glueball spectrum from a potential model'
在最近的一篇文章中，W. S. Hou和G.- G. Wong [Phys. Rev. D { \bf 67}，034003（2003）]在具有动力学胶子质量的势模型中研究了能量低于3GeV的双胶子胶球的能谱。我们指出，在作者计算的18个状态中，只有三个是物理的。其他的状态要么是假的，要么仅仅由于变分参数的任意限制而具有有限的质量。
We study the spectra of two-gluon glueballs and three-gluon oddballs and corresponding equation of state in $5$-dimensional deformed holographic QCD models in the graviton-dilaton system, where the metric, the dilaton field and dilaton potential are self-consistently solved from each other through the Einstein field equations and the equation of motion of the dilaton field. We compare the models by inputting the dilaton field, inputting the deformed metric and inputting the dilaton potential, and find that with only 2 parameters, the $5$-dimensional holographic QCD model predictions on gluebal…
We study two- and three-gluon glueballs of $C=+$ using the method of QCD sum rules. We systematically construct their interpolating currents, and find that all the spin-1 currents of $C=+$ vanish. This suggests that the ``ground-state'' spin-1 glueballs of $C=+$ do not exist within the relativistic framework. We calculate masses of the two-gluon glueballs with $J^{PC} = 0^{\pm+}/2^{\pm+}$ and the three-gluon glueballs with $J^{PC} = 0^{\pm+}/2^{\pm+}$. We propose to search for the $J^{PC} = 0^{-+}/2^{-\pm}/3^{\pm-}$ three-gluon glueballs in their three-meson decay channels in future BESIII, Gl…
By studying the $η_c$ exclusive decay to double glueballs, we introduce a model to mimic phenomenologically the gluon-pair-vacuum interaction vertices, namely the $0^{++}$ model. Based on this model, we study glueball production in pseudoscalar quarkonium decays, explicitly $η_c \to f_0(1500)η(1405)$, $η_b\to f_0(1500)η(1405)$ and $η_b\to f_0(1710)η(1405)$ processes. Among them $f_0(1500)$ and $f_0(1710)$ are well-known scalars possessing large glue components and $η(1405)$ is a potential candidate for pseudoscalar glueball. The preliminary calculation results indicate that these processes are…
