Space-Time Evolution of Hot Hadronic Matter Studied in PHENIX

为了研究高温下多夸克的非微扰QCD现象，我们与BNL-RHIC的PHENIX合作进行了这项研究。2000年至2002年，科学家成功地获得了超过1亿次金核碰撞事件的高统计数据。通过带电的介子对和介子对的三维两粒子相关函数，研究了碰撞过程中产生的热致密核物质的时空演化。我们发现源尺寸参数与原始核碰撞的冲击参数和观测到的对的动量有非常明显的依赖关系。在CERN-SPS能量的研究中可以看到，碰撞段内部产生了流体动力膨胀，并且强径向流影响了冻结时二次粒子的动量关联。在介子的测量中没有观察到粒子发射的长持续时间，这一事实证明排除了一些预测随着对动量的增加而持续时间更长的模型。我们需要一个新的理论场景来理解发生了什么。利用日本东北大学LNS实验室的光子束流，研究了由Furukawa公司生产的3 × 3钨酸铅晶体（ppo）组成的电磁量热计原型。GeV光子的能量分辨率达到32MeV。为了开发一种新的光电倍增管替代光子探测系统，研究了一种带有新设计的前置放大器的雪崩光电二极管读出系统。现在我们准备构建一个证明模型。作为本研究的延伸，我们提交了一项新的计划，该计划由补助金资助，名为“高温QCD物质”，从2015年开始。

In order to investigate non-perturbative QCD phenomenon of multiple quarks at high temperature, we have carried out this study in cooperation with the PHENIX collaboration at BNL-RHIC. Very high-statistic data of more than 100 million events in gold on gold-nuclear collisions were successfully taken in 2000 to 2002. Spatial and temporal evolution of the hot and dense nuclear matter created during the collisions was studied through three-dimensional two-particle correlation functions of charged pion-pairs and kaon-pairs. We found very clear dependences of the source size parameters both on the impact parameter of primary nuclear collisions and on the momentum of observed pairs. It is concluded that a hydro-dynamical expansion is created inside the colliding section and the strong radial flow affects the momentum correlation of secondary particles at freeze-out, as we have seen in studies at the CERN-SPS energies. Long duration time of particle emission was not observed in the measurements of pions, and this fact turns out to exclude several models predicting longer duration time as the pair momentum increases. A new theoretical scenario is demanded to understand what's going on.An electro-magnetic calorimeter prototype composed of a 3 by 3 tower of lead-tungstate crystal (PWO) produced by Furukawa, was studied with photon beams at LNS, Tohoku University. It achieved the energy resolution of 32MeV for GeV photons. To develop a new photon detection system being replaced with aphotomultiplier tube, a readout system of an avalanche-photo-diode with a newly designed pre-amplifier was studied. We are now ready to build a proof model.As an extension of this study, we have submitted a new plan supposed by a Grants-in-Aid entitled "QCD matter at High-Temperature" starting in H15.