Qcd Sum Rule Studies Of Heavy Quarkonium Like States

The method of the QCD sum rules was and still is one of the most productive tools in a wide range of problems associated with the hadronic phenomenology. Many heuristic ideas, computational devices, specific formulae which are useful to theorists working not only in hadronic physics, have been accumulated in this method. Some of the results and approaches which have originally been developed in connection with the QCD sum rules can be and are successfully applied in related fields, such as supersymmetric gauge theories, nontraditional schemes of quarks and leptons etc. The amount of literature on these and other more basic problems in hadronic physics has grown enormously in recent years. This volume presents a collection of papers which provide an overview of all basic elements of the sum rule approach and priority has been given to those works which seemed most useful from a pedagogical point of view.

The discovery of the two families of heavy-quark-antiquark bound states, the &Ugr; and &PSgr; quarkonium spectroscopies, has played a crucial role in unravelling the nature of strong interactions. The articles collected together in this volume are concerned with the connection between quarkonia and quantum chromodynamics. They deal with potential models, spin-dependent forces, next-to-leading order QCD corrections for decay widths and energy level differences, hadronic transitions and the quark-antiquark interaction in QCD, based on perturbation theory, lattice gauge theory and QCD sum rules. Finally, a brief guide is given to the existing literature on possible new quarkonium systems which have been conjectured in connection with gluonic degrees of freedom, and with expectations for new heavy particles with colour, such as the top quark and scalar quarks.

Abstract: In order to investigate the possibility of the recently observed X(5568) being a 0 + tetraquark state, we make an improvement to the study of the related various configuration states in the framework of the QCD sum rules. Particularly, to ensure the quality of the analysis, condensates up to dimension 12 are included to inspect the convergence of operator product expansion (OPE) and improve the final results of the studied states. We note that some condensate contributions could play an important role on the OPE side. By releasing the rigid OPE convergence criterion, we arrive at the numerical value 5.57 − 0.23 + 0.35 GeV for the scalar-scalar diquark-antidiquark 0 + state, which agrees with the experimental data for the X(5568) and could support its interpretation in terms of a 0 + tetraquark state with the scalar-scalar configuration. The corresponding result for the axial-axial current is calculated to be 5.77 − 0.33 + 0.44 GeV, which is still consistent with the mass of X(5568) in view of the uncertainty. The feasibility of X(5568) being a tetraquark state with the axial-axial configuration therefore cannot be definitely excluded. For the pseudoscalar-pseudoscalar and the vector-vector cases, their unsatisfactory OPE convergence make it difficult to find reasonable work windows to extract the hadronic information.

The author develops a novel analysis method for QCD sum rules (QCDSR) by applying the maximum entropy method (MEM) to arrive at an analysis with less artificial assumptions than previously held. This is a first-time accomplishment in the field. In this thesis, a reformed MEM for QCDSR is formalized and is applied to the sum rules of several channels: the light-quark meson in the vector channel, the light-quark baryon channel with spin and isospin 1/2, and several quarkonium channels at both zero and finite temperatures. This novel technique of combining QCDSR with MEM is applied to the study of quarkonium in hot matter, which is an important probe of the quark-gluon plasma currently being created in heavy-ion collision experiments at RHIC and LHC.

This unique volume captures the content of the XXXth International Workshop on High Energy Physics. The scope of this volume is much wider than just high-energy physics; it actually concerns and includes materials from all the most fundamental areas of modern physics research: high-energy physics proper, gravitation and cosmology. Presentations embrace both theory and experiment.

The aim of the book is to give an introduction to the method of QCD Spectral Sum Rules and to review its developments. After some general introductory remarks, Chiral Symmetry, the Historical Developments of the Sum Rules and the necessary materials for perturbative QCD including the MS regularization and renormalization schemes are discussed. The book also gives a critical review and some improvements of the wide uses of the QSSR in Hadron Physics and QSSR beyond the Standard Hadron Phenomenology. The author has participated actively in this field since 1978 just before the expanding success of the SVZ QSSR.