Study of state with high temperature and high density using jets and quarkonia as probes

从2002年到2005年，在RHIC的PHENIX上进行了实验运行，并以喷流和夸克尼亚为探测器进行了研究。从d+Au碰撞和Au+Au碰撞的核修正因子的实验测定中，一致得出结论：高动量区产额的抑制主要归因于部分子的能量损失(喷流猝灭)。为了建立系统趋势，已经积累了碰撞能量、碰撞核物种和作为中心性函数的各种组合的数据。还测量了单电子的核修正因子，发现魅力夸克也遭受了相当大的能量损失。这一结果要求我们重新评估被广泛采用的能量损失机制。确定了p+p碰撞的J/Ψ产额，用于阐明反应机理，并被认为是重离子数据的参考。获得了d+Au碰撞的J/Ψ产额数据，并与同时考虑初始核效应和末期核吸收的理论计算结果进行了比较。最后，给出了Au+Au和Cu+Cu碰撞的一些数据，并与各种理论计算进行了比较。目前，在包括两种机制的计算中似乎得到了最好的拟合：量子粒子中的J/Ψ抑制和强子化过程中的复合过程。与在重离子加速器上的实验研究相平行，对大型强子对撞机进行了准备工作。首先，根据RHIC的结果列出了重要的主题。高动量粒子和夸克尼亚的测量被选为主要课题。研制了跃迁辐射探测器，并对其性能进行了研究。最后，对具有生产规模的样机进行了测试，证明其满足要求。

During the time period from 2002 to 2005, experimental runs were executed at the PHENIX of RHIC, and studies have been performed using jets and quarkonia as probes.From the experimental determination of nuclear modification factor for d+Au collisions and for Au+Au collisions, it was unanimously concluded that suppression of yield in the high momentum region is mainly ascribed to the energy loss of partons (jet quenching). Accumulation of data have been made for various combinations of colliding energy, colliding nuclear species and as a function of centrality, in order to establish systematic trend. Nuclear modification factor was also measured for single electrons, to find out that charm quark also suffer rather large energy loss. This result demands us to re-evaluate the well adopted energy-loss mechanism.J/Ψ yield was determined for p+p collisions, which is used to make clear the reaction mechanism and is supposed to serve as a reference to heavy-ion data. J/Ψ yield data was taken for d+Au collisions, and was compared with a theoretical calculation which includes both initial nuclear effects and nuclear absorption in the final stage. Finally, some data were obtained for Au+Au and Cu+Cu collisions, and the results have been compared with various theoretical calculations. At this moment, the best fit seems to be obtained in the calculations which include both mechanisms ; J/Ψ suppression in the QGP and recombination process in the hadronization prpcess.In parallel to the experimental investigations at RHIC, preparative works have been performed towards LHC. First of all, important subjects were listed up based upon the results at RHIC. Measurement of high momentum particles and quarkonia were chosen to be the main topics. Development of TRD (transition radiation detector) was made, and performance studies were performed. In the end, prototypes with production-size was tested to prove that they fulfill the requirements.