强磁场下QCD相图和强子性质的研究

Recently, investigation of the QCD phase diagram and hadron properties in the presence of strong magnetic fields has attracted more and more attention, because it is of paramount importance to understand the phenomenology of noncentral heavy ion collisions at RHIC and LHC, where a very strong magnetic field can be generated. In this project, we will focus on inverse magnetic catalysis and vacuum superconductor...Firstly, we will explore inverse magnetic catalysis in the framework of the Nambu-Jona-Lasinio (NJL) model by two different physical mechanisms. On the one hand, we will calculate the contribution of neutron pions to the quark condensate and the chiral phase transition temperature in a magnetic field, which is beyond the mean field approximation, in order to verify whether it gives rise to inverse magnetic catalysis. On the other hand, we will try to study the effect of chiral magnetic wave (CMW) on the chiral phase transition, which may be a new ingredient for inverse magnetic catalysis and has never been taken into account before...Secondly, the vector ρ meson in external magnetic field will be also investigated with considering inverse magnetic catalysis in the NJL model. Near the chiral phase transition temperature, since the quark condensates, will be influenced by inverse magnetic catalysis under strong magnetic fields, it is nature that this effect will modify the critical magnetic field of vacuum superconductivity at finite temperature...In addition, we will use different QCD models, to calculate the mass spectra of light mesons and baryons as well as heavy quarkonia and heavy-light mesons in a magnetic field.

近年来，研究强磁场对QCD相图和强子性质的影响越来越受到大家的关注，因为该课题对于理解RHIC and LHC中非对心相对论性重离子碰撞中的实验现象至关重要。在本项目中我们将着重研究反磁催化效应和真空超导现象。. 首先，我们将在NJL模型的框架下用两种不同物理机制来分析反磁催化效应。一方面，我们将会计算在磁场下超越平均场近似的中性pion介子对夸克凝聚和手征相变温度的贡献，从而检验它的贡献是否能产生反磁催化效应。另一方面，我们将研究手征磁波对于手征相变的影响，这个新的机制以前还从来没有被讨论过。. 其次, 我们将探究在考虑反磁催化的情况下, 矢量rho介子受磁场的影响。手征相变温度附近，夸克凝聚将会受到反磁催化的影响，自然会带来真空超导临界磁场随温度的变化。. 此外，我们将会用不同QCD模型计算磁场下轻介子和轻重子，以及重夸克偶素和重-轻介子质量谱。

在过去的几十年间，强磁场对QCD真空及QCD物质的影响收到大家极大的关注。在强磁场情况下，强相互作用物质会呈现很多奇妙现象，例如磁催化、反磁催化、真空超导等等，对这些现象的探究将有助于揭示QCD相图和相结构，从而加深我们对强相互作用本质的理解。在本项目中，我们主要在两味NJL模型的框架下利用随机相位近似方法研究强磁场下强子的性质。首先，我们系统研究了标量sigma介子，带电和中性pion介子，以及标量双夸克在有限温度和有限化学势情况下随磁场强度的质量变化行为，并分析了夸克-反夸克圈图或夸克-夸克圈图对介子或双夸克质量的贡献。然后，我们利用朗道能级形式和固有时形式的夸克传播子，计算了中性pion介子的在有限温度和有限磁场下的极点质量和屏蔽质量。另外，我们利用纵向和横向的介子声速研究了温度和磁场造成的时空各向异性。最后，我们利用固有时形式夸克传播子研究了带电pion介子在磁场中的质量谱。该方法克服了带电pion介子的施温格相位带来的困难，并修正了以前文献计算方法中的不足。