臺灣博碩士論文加值系統

相對論性重離子對撞提供了一個機會，讓我們得以了解強作用力物質在非常高的溫度以及能量密度下的物理現象。從最近由位於美國紐約州長島的布魯克海汶國家實驗室 (Brookhaven National Laboratory, BNL) 的相對論性重離子對撞機 (Relativistic Heavy Ion Collider, RHIC) 上的四個實驗，最近發表了在目前重離子對撞的最高質心能量—兩千億電子伏特 (200 GeV) 的實驗結果顯示，一個非常高溫度、高能量密度、以及可能極為新穎的物質狀態，已經產生於最集中的金離子與金離子對撞事件中。此物質狀態的時間與空間的動力行為極富研究之意義。
在重離子對撞中，Hanbury-Brown和Twisss (HBT) 干涉技術已經被廣泛地使用於探討對撞後所產生的粒子的時間與空間動力行為。PHOBOS實驗是在 RHIC 上的四個實驗之一，配置有由矽偵測器所組成的兩臂的量測器，利用來量測粒子的動量與分辨粒子的種類。
雙相同π介子的相干性在金離子與金離子對撞質心能量 62.4 和 200 GeV的結果將在本論文中提出與探討。本論文利用在對撞中15% 最中心對撞的實驗事例，其平均參與對撞的核子數約為310，並利用Bertsch-Pratt和Yano-Koonin-Podgoretskii座標系統分析雙粒子之速率介於0.4和1.3和橫向動量介於0.1和1.4 GeV/c之間。結果顯示，Bertsch-Pratt參數Rout和Rlong隨著雙粒子橫向動量的增加而減少，然而Rside則呈現和雙粒子橫向動量的微弱勢相關。另外，Rout和Rside顯示與對撞能量無關，而Rlong則是小幅度地隨著對撞能的增加而增加。而對撞後所產生的火球 (source) 的速度和雙粒子的速度呈現極強的動力相干性。

The relativistic heavy-ion collisions provide an opportunity to understand the behavior
of strongly interacting matter at extremely high temperature and density. According to
the recent experimental results from all four experiments at the Relativistic Heavy Ion
Collider (RHIC) at the top RHIC energy, sqrtsNN = 200 GeV, it has been widely accepted
that a very hot, dense, and possibly new state of matter have produced in central Au+Au
collisions at RHIC. The space-time evolution of such collisions is great interest.

The technique of Hanbury-Brown and Twiss (HBT) interferometry is extensively used to
provide insight into the spatiotemporal dynamic evolution of the particle emitting
source in heavy-ion collisions. The $mathcal{PHOBOS}$ experiment, consisting of a
two-arm spectrometer constructed by silicon detectors, is being used to perform many
interesting studies at RHIC.

This thesis presents the measurement of two-particle correlations of identical charged
pion pairs from Au+Au collisions at sqrtsNN = 62.4 and 200 GeV. Data for the 15% most
central events were analyzed with Bertsch-Pratt and Yano-Koonin-Podgoretskii
parameterizations using pairs with rapidities of $0.4 < Y_{pipi} < 1.3$ and pair transverse
momentum $0.1 < K_T < 1.4$ GeV/c. The Bertsch-Pratt radii $R_{out}$ and $R_{long}$ decrease
as a function of pair transverse momentum, while $R_{side}$ appears to have a weaker
dependence. $R_{out}$ and $R_{side}$ are independent of collision energy, while $R_{long}$
shows a slight increase as compared with the results at lower energy. The source rapidity
$Y_{YKP}$ scales roughly with the pair rapidity $Y_{pipi}$, indicating strong dynamical
correlations.

Chapter 1 Introduction --- 1
Chapter 2 The Experiment --- 8
Chapter 3 A Review of HBT Correlations --- 27
Chapter 4 Data Analysis --- 47
Chapter 5 Results and Discussion --- 72
Chapter 6 Conclusion --- 106

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[2] J.C. Collins and M.J. Perry, PRL, 34 p1353, 1975
[3] E.V. Shuryak, PLB, 78 p150, 1978