Effect of hadronization on the form of correlation moments for instanton processes and possibility of discovering them experimentally

The possibility of discovering QCD instantons in deep-inelastic scattering by analyzing correlations in final states is studied. The correlation moments F _q and H _q for instanton processes are calculated at the parton and at the hadron level. Hadronization is taken into account by the Monte Carlo method. The moments for instanton and for usual processes are found to behave differently, which can be used to identify experimentally instantons.     

Gluon field strength correlation functions within a constrained instanton model

We suggest a constrained instanton (CI) solution in the physical QCD vacuum which is described by large-scale vacuum field fluctuations. This solution decays exponentially at large distances. It is stable only if the interaction of the instanton with the background vacuum field is small and additional constraints are introduced. The CI solution is explicitly constructed in the ansatz form, and the two-point vacuum correlator of the gluon field strengths is calculated in the framework of the effective instanton vacuum model. At small distances the results are qualitatively similar to the single instanton case; in particular, the invariant structure is small, which is in agreement with the lattice calculations. Received: 18 June 1999 / Revised version: 21 July 1999 / Published online: 17 February 2000     

A Non-Zero Hadronic Elliptic Flow with a Vanished Partonic Elliptic Flow in a Coalescence Scenario

The elliptic flow of a hadron is calculated using a quark coalescence model based on the quark phase space distribution produced by a free streaming locally thermalized quark in a two-dimensional transverse plane at initial time. Without assuming the quark＇s elliptic flow, it is shown that the hadron obtains a non-zero elliptic flow in this model. The elliptic flow of the hadron is shown to be sensitive to both space momentum correlation and the hadron＇s internal structure. Quark number scaling is obtained only for some special cases.     

核子(强子)结构和性质的QCD研究

核子 (强子 )是夸克、胶子的束缚态 ,由量子色动力学 QCD描述。由于 QCD的基本特性(高能标度下的渐近自由、低能标度下色禁闭及动力学手征对称性破缺 ) ,对核子 (强子 )结构和性质的 QCD图象是标度相关的 .在高能标度下描述强子的是与探测强子结构的硬过程相联系的QCD部分子模型 .强子的夸克、胶子结构信息通过 QCD部分子求和规则得到 .QCD微扰论是适用的理论 .在低能标度时 ,必须发展 QCD非微扰途径来描述核子 (强子 )物理 .这里简要地讨论各种非微扰途径 (格点 QCD、Dyson- Schwinger方程、有效场论、QCD求和规则 )的某些结果和进展 ,并指出 QCD真空结构在描述低能标度下强子物理中担任重要角色 . The nucleon (hadron) is the bound state of guarks and gluons, which is described by the quantum chromodynamics (QCD). Due to the basic properties of QCD (the asymptotic freedom at the high energy scale, the color confinement and the dynamical chiral symmetry breaking at the low energy scale), the QCD picture for the nucleon’s (hadron’s) structure and property is scale dependent. At high energy scale, the QCD parton model, which is relative to the hard process for testing the...     

Parton-cluster model of hadrons and impact parameter structure of non-diffractive collisions

A model of hadron structure and hadron collisions is proposed for interpreting experimental data. It starts from the assumption that a hadron consists of a number of partons with very large masses which are grouped inside hadrons into clusters with quantum numbers of the known hadrons. In hadron collisions the most peripheral clusters behave as spectators and represent leading particles; non-diffractive hadron collisions can then be interpreted mostly as stripping-like reactions. It is shown on a sample of annihilation and non-annihilation pp collisions at 5·7 GeV/c that experimental data for several different leading particles are in good qualitative agreement with the basic requirement of the model which concerns the strong impact parameter angular dependence of the leading particles.Dedicated to Academician Václav Votruba on the occasion of his seventieth birthday.     

High energy hadron spin flip amplitude

The high energy part of the hadron spin flip amplitude is examined in the framework of the new high energy general structure (HEGS) model of the elastic hadron scattering at high energies. The different forms of the hadron spin flip amplitude are compared in the impact parameters representation. It is shown that the existing experimental data of the proton-proton and proton-antiproton elastic scattering at high energy in the region of the diffraction minimum and at large momentum transfer give support in the presence of the energy-independent part of the hadron spin flip amplitude with the momentum dependence proposed in the works by Galynskii–Kuraev.     

Effects of QCD Vacuum and the Instanton Induced-Contributions to the Nucleon Structure Functions

The instanton induced cross section in deep inelastic kinematics is a subject which people are tendentious to investigate it. Instanton induced contributions are well defined for the nucleon structure function. The non-perturbative contribution to the quark distributions of structure function, F2 (x, Q2 ), is considered within an instanton model for the QCD vacuum. We find that the structure function may possess numerically large non-perterbative contributions which are related to the violation of chirality and correspond to the correction of parton distribution of the leading twist. It is shown that the instantons give a negative contribution to the structure function at the NLO approximation. A comparison between our results, considering instantaon effect, and the case when we do not take this effect is done. Taking into account the instanton size, ρ, via the modified running coupling constant we get to a good agreement between our results at the NLO and NNLO approximations and the available experimental data, specially at the low values of the Bjorken variable x0.1 which confirms the validity of our calculations.     

Instanton in the Georgi-Glashow model

Topologically nontrivial solutions in the Georgi-Glashow model are studied. It is shown that only in quantum theory does an instanton exist as a stable field configuration. An effective action is constructed, and quantum equations of motion for the instanton are obtained on its basis. Their solutions at long and short distances are obtained. A critical size corresponding to a stable instanton in the Georgi-Glashow model is found.     

Multi-hadron production in matter and quark-glue model of hadron

We discuss a connection between our model for the space-time development of multiparticle production in nuclear matter and quark-glue model of the hadron structure.     

Off-diagonal quark distributions in pions in the effective single-instanton approximation

Nonperturbative functions that parametrize off-diagonal hadronic matrix elements of the light-cone leading-twist quark operators are considered. These functions are calculated within the proposed relativistic quark model allowing for the nontrivial structure of the QCD vacuum, special attention being given to gauge invariance. Hadrons are treated as bound states of quarks; strong-interaction quark-pion vertices are described by effective interaction Lagrangians generated by instantons. The parameters of the instanton vacuum, such as the effective radius of the instanton and the quark mass, are related to the vacuum expectation values of the quark-gluon operators of the lowest dimension and to low-energy pion observables.     

False vacuum decay in a brane world cosmological model

The false vacuum decay in a brane world model is studied in this work. We investigate the vacuum decay via the Coleman-de Luccia instanton, derive explicit approximative expressions for the Coleman-de Luccia instanton which is close to a Hawking-Moss instanton and compare the results with those already obtained within Einstein's theory of relativity.     

Distribution of instanton sizes in a simplified instanton gas model

We investigate the distribution of instanton sizes in the framework of a simplified model for ensembles of instantons. This model takes into account the non-diluteness of instantons. The infrared problem for the integration over instanton sizes is dealt with in a self-consistent manner by approximating instanton interactions by a repulsive hard core potential. This leads to a dynamical suppression of large instantons. The characteristic features of the instanton size distribution are studied by means of analytic and Monte Carlo methods. In one dimension exact results can be derived. In any dimension we find a power law behaviour for small sizes, consistent with the semi-classical results. At large instanton sizes the distribution decays exponentially. The results are compared with those from lattice simulations. Received: 15 May 2000 / Revised version: 17 July 2000 / Published online: 25 September 2000     

Charge confinement and vacuum structure in the 1 + 1 dimensional Higgs model

We demonstrate that the 1 + 1 dimensional Higgs model is equivalent to the massive sine-Gordon model, and hence to the massive Schwinger model in a special case. We do this by deriving a dual Lagrangian which embodies instanton effects. Based on this equivalence, we discuss charge confinement and vacuum structure in the Lagrangian formalism.     

袋模型进展

本文回顾了强子结构袋模型几年来所取得进展,着重介绍近两年来的进展。总结是沿以下三个方面进行的,(一)理论描述的进一步完善,包括半定量地介绍了R.L.Jaffe等人最近提出的,考虑到手征对称的混合袋模型。(二)袋模型对强子静态性质的应用,包括轻夸克强子和重夸克强子的质量谱,以及对π介子质量的重新考虑。(三)多夸克强子,分析了它们分类情况,并估计了它们的质量。袋模型对于强子衰变,强子碰撞等动态过程,以及对原子核的应用成就不多,进展不大,而且篇幅有限,未作定量介绍。     

Study of Topological Structure of Vacuum by Lattice QCD

Overlap fermions and improved 5Li cooling are compared, which exhibits that these two filter methods can produce similar structures. Then the overlap fermions and improved 5Li cooling are combined to calculate the topological charge and identify the structure of the vacuum. The results are consistent with instanton liquid model .     

Some implications of the quark model for high energy scattering

The expressions for total scattering cross sections obtained from the quark model are expressed in a simple form which shows the dependence of the results on the assumptions. The results are shown to depend only on the value of six constants or “charges” defined for each hadron and to be otherwise independent of the structure. Any model which gives the same values of these charges gives the same result as the quark model. In particular, the results for processes which have odd signature t-channel quantum numbers hold in a quark model even with arbitrary mixtures of additional quarkantiquark pairs in the hadron wave function, provided that B, Y, and I are conserved.     

Calorons and the bilocal correlator of the gluon-field strength

The bilocal correlator for finite-temperature gluodynamics is calculated in the instanton gas model. It is shown that the correlation length of vacuum in this model decreases when temperature increases. The results are compared with finite-temperature lattice calculations for the bilocal correlator. The instanton density and possible structures of nonperturbative vacuum are discussed.