Study of Hadron Properties in QCD with Finite Temperature and/or Density.

量子色动力学（QCD）将颜色限制在低温低密度，真空处于手性对称性破缺阶段。当温度和/或密度升高时，真空会经历一个相变到一个新的基态，在这个基态中，颜色被解除限制，必须恢复手性对称。用非微扰方法澄清相变的性质。在这个研究项目的第一阶段，发现了一种全新的外来强子，五夸克，这一新情况引起了人们的极大兴趣。从这一事件开始，外来强子、它们的结构和产生机制以及普通强子的外来多夸克组分的研究成为热点。我们从有限温度和有限密度量子光盘的角度研究了外来强子。详细列出了研究的主要结果。(1) QCD和规则方法中奇异强子的五夸克和谱：我们首次利用QCD和规则技术对基于QCD的五夸克质量和量子数进行了分析。我们发现正宇称五夸克不太可能在低质量区域。我们还提出了一种区分强子中不同数量夸克组分的方法。我们将该方法应用于标量介子和λ ^*重子，它们包含主要的奇异成分。(2)五夸克和外来强子的点阵QCD分析：我们分析了猝灭点阵QCD中的五夸克谱。为了区分共振和连续体，我们提出了一种扭曲边界处方，并验证了其有效性。

Quantum Chromodynamics (QCD) is confining color in low-temperature and low density and the vacuum is in the chiral-symmetry breaking phase. It is believed that when the temperature and/or density get higher, the vacuum goes through a phase transition to a new ground state where color is de-confined and chiral symmetry must be restored. Non-perturbative approaches to clarify the properties of the phase transition. At the first stage of this research project, a totally new exotic hadron, pentaquark, was discovered and much interest was paid in this new situation. Starting with this event, the subjects of exotic hadrons, their structure and production mechanism, as well as exotic multi-quark components of ordinary hadrons become hot. We have studied the exotic hadrons from the viewpoints of finite temperature and density QCD.The main results of the research were itemized.(1)Pentaquark and spectrum of the exotic hadrons in the QCD sum rule approach :We performed the first analysis of the pentaquark mass and quantum numbers based on the QCD, using the QCD sum rule technique. We found that the positive-parity pentaquarks are not likely to be in the low-mass region. We also proposed a method which distinguish the components of different number of quarks in a hadron. We applied the method to scalar mesons as well as Lambda^* baryon and they contain major exotic components.(2)Lattice QCD analysis of pentaquarks and exotic hadrons :We have analyzed pentaquark spectrum in the quenched lattice QCD. In order to distinguish a resonance from continuum, we proposed a twisted-boundary prescription and confirmed its effectiveness.