中能区椭圆流和转变能的系统质量依赖外文翻译.doc

毕业设计(论文)外文资料翻译系 ： 核能与可再生能源 专 业： 核工程与核技术 091 姓 名： 林 森 学 号： 0902500124 (用外文写)外文出处： PHYSICAL REVIEW C 74 014602(2006) 附 件： 1.外文资料翻译译文；2.外文原文。 指导教师评语： 签名： 年 月 日附件1：外文资料翻译译文中能区椭圆流和转变能的系统质量依赖张英逊李祝霞1中国原子能科学研究院能源、邮政信箱275(18)、北京102413,中华人民共和国2中心理论核物理、国家实验室的兰州重离子加速器,兰州730000,中华人民共和国3理论物理研究所,中国学术的科学,北京100080,中华人民共和国(收录于2005年12月12日,2006年7月7日出版)椭圆流Z 2粒子在重离子碰撞的能量从数十到数百兆电子伏特每核子研究通过传输模型。一个新版本的改进的量子分子动力学模型(ImQMD05)。该模型采用了一个完整的 Skyrme 势能密度泛函数。不同的等效相互作用的影响和介质修正的核子核子横截面的椭圆流进行了研究。我们的结果表明,软核状态方程和入射能量依赖于介质核子核子横截面用于描述激发态的中能椭圆流函数。椭圆流跃迁能的大小对中能的依赖关系也进行了探讨。系统质量依赖跃迁能与系统质量相符合，指数为0.223。中能重离子碰撞(HICs)研究领域的一个主要目标是提取更准确信息的核状态方程(EoS)。最近，已经从重离子反应数据中对确定核物质状态方程取得重大进展。集体流在有效的观测量中扮演了一个突出的角色。大量的理论和实验工作耗费在了中能重离子碰撞中集体流的研究上面。椭圆流已被证明是一个推倒状态方程和重离子碰撞力学多产的课题。最近,激发函数椭圆流参数的能量从费米能级到相对论能量的 197 Au + 197 Au 式中已经通过 FOPI, INDRA, 和 ALADIN 协作的测量,跃迁能从正到负的椭圆流被确认,它大约在 100MeV/u。平均场和两体碰撞在这个能区中都扮着重要的角色。在低能区平均场起关键性作用,然后随着能量的增加，两体碰撞逐渐成为主导。因此, 在这个能区，随着对椭圆流激励函数的深入研究，可以对与核子核子等效相互作用的核物质状态方程和介质修正核子核子横截面相关方面提供更多有用的信息。在中能区，椭圆流的跃迁能可能对提取核反应信息特别有用。当能量高于跃迁能，椭圆流将有益于提取试验核子核子碰撞截面，因为两体碰撞在这个能区对集体流发挥更重要的作用。这项工作的另一个目的是通过椭圆流流入重离子碰撞中能量从费米能量到相对论能量的过程，来探讨试验核子核子横截面。在这篇报告中,我们应用最新版本改进的量子分子动力学模型(ImQMD05) 对中能 197 Au + 197Au 核反应，来研究激发函数椭圆流参数，并通过比较测量和模型计算来提取等效相互作用中核状态方程和介质修正核子核子横截面的信息。系统质量依赖的椭圆流中的跃迁能，也将对 58Ni+ 58Ni 和 197 Au + 197Au 进行研究。为方便读者,我们首先给出一个简要介绍 ImQMD05 的模型。ImQMD 模型的主要改进对比与普通的IQMD模型来源于于 (1)同位旋相关作用和依赖的表面能量在能量密度方面功能, (2)单粒子占有数的限制, (3)系统质量依赖的波包宽度。这个ImQMD模型能完美地描述在中能重离子碰撞中的离子簇的产生量。在 ImQMD05 模型中,我们介绍了完整的 Skyrme 势能密度泛函，除了局部相互作用的自旋轨道,它允许我们选择各种 Skyrme 参数，来描述基态的核子和饱和核物质，类似但不同性质的饱和密度。构造的片段通过结合模型广泛应用于 QMD 模型的计算中,相对动量小于P0和相对距离小于R0的离子结合成一个离子簇(在这里,取 R0 = 3.0fm P0 = 250MeV/ c)。这里分别显示了在 Ebeam = 60、150、400MeV/u 的对心碰撞中，197 Au + 197Au 的电荷分布的片段。从中可以看到,计算结果对电荷分布的片段与实测数据吻合较好。然后,我们应用 ImQMD05 模型来研究椭圆流参数的激励函数和试着提取有效相互作用和试验的两体横截面的有效信息。随着能量进一步增大, v2变成负值，当 SkP 和 SkM 大约等于 400MeV/u 和SLy7 和 SIII 大约等于 250MeV/u 时,它达到最大负值。用 SIII 和 SLy7 比 SkP 和 SkM 的计算在压缩区提供更强的压力,这使得 SLy7 和 SIII 计算椭圆流时在较低能量达到最大了负值v2。在比较了用四种 Skyrme 参数测量的预测结果后，,我们发现用 SkP 和 SkM 计算的结果，与实验数据几乎一致。在达到最大负值椭圆流后,v2值再次减少。这意味着在v2达到最大负值后旁流的速度更快了。观测了从90MeV/u到1.93 GeV /u的核阻止后，我们观察到 197 Au + 197 Au 的最大核阻止大约在400MeV/u。我们看到椭圆流参数达到最大负值的能量的与达到最大核阻止的能量一致。很明显,如果反应体系在某一能量时达到最大核阻止, 在反应中的物质形成将会达到最小的透明度,因此大多数粒子优先发射出平面。现在,让我们探讨试验椭圆流的核子核子横截面的影响。这里显示了当 = 0.2,0.0,0.4 时椭圆流激发函数的参数的计算,我们有效地研究了在不同核能环境下试验核子核子横截面以及散射对的相对动量。SkP Skyrme 参数在计算中被采用。我们看到,在能量低于跃迁能时, 当= 0.2 和= 0.0 时，无论给实验数据合理的解释，还是当轰击能量高于跃迁能时差别增大，计算结果之间的差异都很小。随着能量进一步增大, 当= 0.2 时，负椭圆流计算结果太弱(即,负椭圆流参数太小)。它需要一个较小的甚至是负。根据实验结果，当约为0.4，入射能大约为400MeV/u时，我们为这个例子找到一个合理的解释;即,在入射能约为400MeV/u时,中能两体截面的提取大于自由截面。据预测, 根据两个碰撞的核子的相对动量，在超常密度中的中能弹性核子核子截面的行为先抑制,然后增强。还预言了,中能弹性核子核子截面随温度上升而增加。如果我们仅仅考虑核子对碰撞的相对动量大约等于弹射体和靶子的相对动量,假设温度明显从几十增加到几百MeV/u, 那么，椭圆流中，从中能核子核子横截面提取的信息和预测定性一致。本研究表明,在中能核子核子截面表达式中，取决于反应能量，是为了在不同的环境中模拟试验核子核子横截面。证实这一发现,我们在SIS能量对 Au+Au 的核阻止的激发函数做了类似的计算，并且我们的计算结果与测量值进行了比较。在这项研究中，和试验两体截面有关的信息来源于核阻止从椭圆流的激发函数得到一样的结果。涉及到核阻止的结果将在其它地方出版。我们注意到,计算结果不完全与在整个能区测量一致。这意味着一个更有条理的处理方法，包括在中等截面和平均场,特别是一个更有条理更明确动量公式的使用是非常有必要的,但这是很难做的。鸣谢我们感谢 Danielewicz 博士的友情讨论。这项工作分别受到了中国国家自然科学基金委员会和国家重点基础研发规划项目的赞助，并编号为10175093，10235030，10235020，和G20000774。附件2：外文原文Elliptic flow and system size dependence of transition energies at intermediate energiesYingxun Zhang Zhuxia Li1China Institute of Atomic Energy, P.O. Box 275 (18), Beijing 102413, Peoples Republic of China2Center of Theoretical Nuclear Physics, National Laboratory of Lanzhou Heavy Ion Accelerator, Lanzhou 730000, Peoples Republic of China3Institute of Theoretical Physics, Chinese Academic of Science, Beijing 100080, Peoples Republic of China(Received 12 December 2005; published 7 July 2006)The elliptic flow for Z 2 particles in heavy ion collisions at energies from several tens to several hundreds MeV per nucleon is investigated by means of a transport model, i.e., a new version of the improved quantum molecular dynamics model (ImQMD05). This model employs a complete Skyrme potential energy density functional. The influence of different effective interactions and medium corrections of nucleon-nucleon cross sections on the elliptic flow are studied. Our results show that a soft nuclear equation of state and incident energy dependent in-medium nucleon-nucleon cross sections are required to describe the excitation function of the elliptic flow at intermediate energies. The size dependence of transition energies for the elliptic flow at intermediate energies is also studied. The system size dependence of transition energies fits a power of system size with an exponent of 0.223.A main goal of the research area of heavy ion collisions (HICs) at intermediate energies is to extract more accurate information on the nuclear equation of state (EoS). Considerable progress has been made recently in determining the equation of state of nuclear matter from heavy ion reaction data . A prominent role among available observables is played by collective flow. Much theoretical and experimental effort has been expended on the study of collective flow in HICs . The elliptic flow has proven to be one of the more fruitful probes for extracting the EoS and the dynamics of heavy ion collisions。Recently, the excitation function of elliptic flow parameters at energies from Fermi energy to the relativistic energy regime for 197Au+197Au has been measured by the FOPI, INDRA, and ALADIN Collaborations , and the transition energy from positive to negative elliptic flow was confirmed, which is around 100 MeV/nucleon. Both the mean field and two-body collision parts play important roles in thisenergy region. The mean field plays a dominant role at low energies, and then gradually the two-body collision becomes dominant with energy increases. Thus, a detailed study of the excitation function of elliptical flow in this energy region can provide more useful information on the nucleon-nucleon interaction related to the equation of state of nuclear matter and the medium correction of nucleon-nucleon cross sections. The transition energy of elliptic flow at intermediate energies may be particularly useful in extracting information on the nuclear effective interaction. While elliptic flow at energies higher than the transition energy will be useful in extracting the medium correction of nucleon-nucleon cross sections because two-body collisions play a more important role on collective flow at these energies . Another aim of this work is to investigate the medium correction of nucleon-nucleon cross sections through elliptic flow in heavy ion collisions at energies from the Fermi energy to relativistic energies.In this report, we apply the new version of the improved quantum molecular dynamics model (ImQMD05) to study the excitation function of elliptic flow parameters for 197Au+197Au at intermediate energies, and through the comparison between measurement and model calculations to extract the information on the effective interaction related to the EoS and the medium correction of nucleon-nucleon cross sections. The system size dependence of transition energies of elliptic flow from 58Ni+58Ni to 197Au+197Au will also be studied.For the convenience of the readers, we first give a brief introduction of the ImQMD05 model. The main developments of the ImQMD model compared with the usual IQMD model are the introduction of (1) the isospin independent and dependent surface energy terms in the energy density functional, (2) the constraint on the single-particle occupation number, and (3) the system size dependent wave packet width . The ImQMD model can successfully describe the yields of clusters in intermediate energy heavy ion collisions . In the ImQMD05 model, we introduce the full Skyrme potential energy density functional except for the spin-orbit term in the local interaction part, which allows us to choose various Skyrme interactions that describe the ground states of nuclei and saturated nuclear matter similarly well but predict rather different properties away from saturated density.The fragments are constructed by means of the coalescence model widely used in the QMD model calculations in which particles with relative momenta smaller than P0 and relative distances smaller than R0 are coalesced into one cluster (here, R0 = 3.0 fm and P0 = 250 MeV/c are adopted). It shows the charge distribution of fragments for 197Au+197Au at Ebeam = 60, 150, 400 MeV/nucleon at central collisions, respectively. One sees from it that the calculation results for charge distribution of fragments are in good agreement with experimental data. Then, we apply the ImQMD05 model to study the excitation function of elliptic flow parameters and try to extract the information on the effective interactions and the medium corrections of two-body cross sections.As energy further increases, v2 becomes negative, and it reaches maximal negative value around 400 MeV/nucleon for SkP and SkM and 250 for SLy7 and SIII. The calculations with SIII and SLy7 provide stronger pressure at the compression zone compared with SkP and SkM, which makes calculated elliptic flow to reach the maximal negative v2 at lower energy for SIII and SLy7. In comparing the predictions made with the four Skyrme interactions with measurements, we find that the results with SkP and SkM are in reasonable agreement with experimental data. After reaching the maximal negative elliptic flow, the negative v2 value decreases again. This implies that the spectator moves faster after the v2 reaches the maximal negative value . The nuclear stopping from 90 MeV/nucleon to 1.93 GeV/nucleon was measured and maximal nuclear stopping was observed around 400 MeV/nucleon for 197Au+197Au. It seems to us that the energy for reaching the maximal negative elliptic flow parameter is coincident with the energy for reaching the maximal nuclear stopping. It is clear that if the reaction system reaches the maximal stopping around certain energies, the matter formed in the reaction should reach minimal transparency, and thus most particles are preferentially emitted out of plane.Now, let us investigate the influence of the medium correction of nucleon-nucleon cross sections on elliptic flow. It shows the excitation functions of elliptic flow parameters calculated with = 0.2, 0.0,0.4 , by which we effectively study the medium correction of nucleon nucleon cross sections at different nuclear environments as well as the relative momentum of the scattering pair. The SkP Skyrme interaction is adopted in the calculations. We see that at energies lower than transition energy, the difference between the calculation results with = 0.2 and = 0.0 is small, both give reasonable agreement with experimental data, and the difference increases when the bombarding energy is higher than transition energy. As energy further increases, the negative elliptic flow calculated with = 0.2 is too weak (i.e., too small of a negative elliptic flow parameter). One needs a smaller or even a negative .We find a reasonable agreement with experimental results can be obtained for the case at incident energy around 400 MeV/nucleon when is taken to be about 0.4; i.e., at the energy of about 400 MeV/nucleon, the in-medium two-body cross section extracted is larger than the free cross section. It was predicted that the behavior of the in-medium elastic nucleon-nucleon cross section at supernormal densities as a function of the relative momentum of two colliding nuclei is first suppression and then enhancement. It is also predicted that the in-medium elastic nucleon-nucleon cross section increases with temperature. If we simply consider the relative momentum of a colliding nucleon pair to be roughly equal to the relative momentum of a projectile and target, and suppose the temperature increases obviously from several tens to several hundreds of MeV per nucleon, the information on the in-medium nucleon-nucleon cross sections extracted from the elliptic flow is qualitatively consistent with the pr