【作者】 李俊生；

【导师】 刘福虎；

【作者基本信息】 山西大学 ， 粒子物理与原子核物理， 2009， 博士

【摘要】 中高能重离子碰撞吸引了众多的理论和实验工作者,通过对中高能重离子碰撞的研究,可以得到关于高温高密环境中粒子产生、相互作用机制及极端现象的知识,中高能重离子碰撞也是目前获得这些知识的唯一途径。在实验上,本文第三章利用阶乘矩和Takagi矩研究了4.5A GeV/c ¹⁶O、²⁴Mg诱发乳胶核反应末态慢粒子分布的分形行为。在分别计算了黑粒子和灰粒子的水平阶乘矩和垂直阶乘矩后,发现一般情况下两种阶乘矩虽然并不相等,但是两种方法所得结论相同。为了消除由于末态粒子分布不均匀性所造成的影响,采用修正因子和累积变量两种方法进行了修正,通过对实验数据的分析,发现修正因子的修正效果不如累积变量,只有在做了变量代换后,水平阶乘矩和垂直阶乘矩才基本相等。通过广义分形维数可以将间歇与分形联系起来。通过对由阶乘矩和Takagi矩得到的广义分形维数的研究发现,在发射角空间,末态慢粒子的发射均存在多重分形的特征。自仿射分形可以较好地反映末态粒子在三维空间的发射,本文第四章计算了4.5A GeV/c ¹⁶O诱发乳胶核反应靶核碎片的二维阶乘矩,发现其发射过程存在自仿射分形,这已得到多数实验的证实,但在有些实验中我们仍无法得出准确的结论。因此,对于靶核碎片的发射过程仍需进一步的研究。通过对非热相变因子的研究发现,在q=3时,λ_q存在最小值,说明在高能核-核碰撞中的靶核碎片发射过程中存在非热相变过程。在理论上,本文第五章根据多源理想气体模型,尝试用一个统一的公式对中能及高能低端⁵⁶Fe+p反应散裂产物和¹³⁶Xe+Pb和¹²⁴Xe+Pb碎裂反应产物的同位素产生截面进行了研究。通过与实验数据的比较发现,计算结果可以很好描述上述实验结果,拟合参数也可以得到很好解释。对于类中子多重数有贡献的每一个发射源都类似于一个放射源。各向异性流是高能碰撞中发现的一个重要的实验现象,本文第六章利用多源理想气体模型描述了高能核-核碰撞中产生的已鉴别粒子的类瑞利型的横动量分布,从而研究了二阶各向异性流（即椭圆流）与横动量的关系。结果表明,多源理想气体模型可以很好地描述STAR和PHENIX合作组测得的s^1/2=200A和62.4A GeV的Au-Au碰撞和s^1/2=200A GeV的Cu-Cu碰撞的实验结果。更多还原

【Abstract】 Heavy ion collisions at intermediate and high energies are interesting subjects in theoretical and experimental nuclear physics because these collisions can provide a unique opportunity to investigate the particle productions,interacting mechanisms,and rare phenomena at high density and high temperature.Experimentally,fractal structure of slow particles from nuclear reactions in emulsion induced by ¹⁶O and ²⁴Mg at 4.5A GeV/c are studied in Chapter 3 by using factorial moments and Takagi moments.After the calculation of horizontal factorial moments and vertical factorial moments,it is found that the same conclusion can be attained although the results of the two kinds of methods are not equal.For nonflat multiplicity distributions,an extra M-dependent correction factor and a new variable are introduced to correct the factorial moments respectively.It is found that the new variable is better than the correction factor,under the new variable the horizontal factorial moments and vertical factorial moments are almost equal.The generalized dimensions can characterize the fractal behavior.The generalized dimensions of slow particles determined by factorial moments and Takagi moments are calculated.Multifractality of slow particles is observed in emission angle space.Self-affine fractal is a good candidate for descriptions of multiparticle production.Two-dimensional factorial moments of target fragments for ¹⁶O-AgBr collisions at 4.5A GeV/c are calculated in Chapter 4.Self-affine fractal is observed in target fragments.This phenomenon has been confirmed in some experiments.But an unambiguous conclusion can not be attained in some experiments.An in-depth study on the emission of target fragments is necessary.The occurrence of distinct minima inλ_q at q=3 indicates the possibility of a non-thermal phase transition in the emission process of target fragments in high energy nucleus-nucleus collisions.Theoretically,using a unified description on multiplicity distributions of final-state particles,the spallation residues in ⁵⁶Fe+p reactions and fragmentation products in ¹³⁶Xe(¹²⁴Xe)+Pb reactions at intermediate energy and at the low end of high energies are studied in Chapter 5.The isotopic production cross sections of fragments produced in the reactions are calculated by using a multisource ideal gas model.It is found that the MSIG model can well describe the experimental results,and the parameters can be explained well too.Each source contributes to multiplicity-like distribution of neutrons like a radioactive object.In high energy nucleus-nucleus collisions,the particle azimuthal anisotropy and its dependence on particle identity and on transverse momentum can provide information on the properties of interacting system. The dependences of elliptic flows on transverse momentum for identified particles produced in nucleus-nucleus collisions at high energy are studied in Chapter 6 by using the MSIG model that describes the distribution of transverse momenta as a Rayleigh-like distribution.The experimental results of Au+Au collisions at s^1/2=200A and 62.4A GeV and Cu+Cu collisions at s^1/2=200A GeV,measured by the STAR and PHENIX collaborations,are well described by using this model.更多还原