M. Colonna, V. Baran, M. Di Toro
We review recent results obtained for charge asymmetric systems at Fermi energies. Observables sensitive to the isospin dependent part of nuclear interaction are discussed, providing information on the symmetry energy behavior below normal density.
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We introduce isospin dependence in the cluster recognition algorithms used in the Quantum Molecular Dynamics model to describe fragment formation in heavy ion collisions. This change reduces the yields of emitted nucleons and enhances the yields of fragments, especially heavier fragments. The enhancement of neutron-rich lighter fragments mainly occurs at mid-rapidity. Consequently, isospin dependent observables, such as isotope distributions, yield ratios of $n/p$, $t/^3He$, and isoscaling parameters are affected. We also investigate how equilibration in heavy ion collisions is affected by thi…
On the splitting of nucleon effective masses at high isospin density: reaction observables
本文综述了非对称物质中核子有效质量分裂$puzzle$的现状，并对非相对论性的$and$和相对论性的介质相互作用中的有效质量分裂进行了有争议的预测。基于微观输运模拟，我们提出了中能（$RIA$）非对称（不稳定）离子碰撞中的一些相当敏感的观测值：i）Lane势的能量系统学; ii）快发射核子的同位旋含量; iii）微分集体流。对轻等压线（如$^3H-^3He$）进行类似的测量也很重要。
Investigation of Low-Density Symmetry Energy via Nucleon and Fragment Observables
与随机输运模拟，我们详细研究中心和周边碰撞费米能量，并提出新的观测，敏感的对称性能量低于正常密度。因此，我们一方面确定了同位旋不平衡比，即不同同位旋核的二元外围反应中的同位旋平衡的相对量，作为能量损失的函数，它对同位旋扩散敏感;另一方面，在三元反应的对称碰撞中中等质量碎片（IMF）的同位旋不对称性，或者更具体地，IMF与剩余不对称性的比值，这对同位旋迁移敏感。
Isospin Transport at Fermi Energies
本文研究了费米能区半周边碰撞中的同位旋输运机制。仔细分析了在两个反应伙伴之间形成低密度区（颈部）和预平衡发射对同位旋平衡动力学的影响。我们清楚地确定了两个主要贡献的同位旋输运：由于$N/Z$比和由于密度梯度的同位旋漂移的同位旋扩散。这两种效应都对核物质状态方程（EOS）的对称性部分敏感，特别是对饱和密度附近的值和斜率敏感。
We investigate isospin-symmetry breaking effects in the sd-shell region with large-scale shell-model calculations, aiming to understand the recent anomalies observed in superallowed Fermi beta-decay. We begin with calculations of Coulomb displacement energies (CDE's) and triplet displacement energies (TDE's) by adding the T=1,J=0 isospin nonconserving (INC) interaction into the usual isospin-invariant Hamiltonian. It is found that CDE's and TDE's can be systematically described with high accuracy. A total number of 122 one- and two-proton separation energies are predicted accordingly, and loca…
Isospin mixing and Fermi transitions: Selfconsistent deformed mean field calculations and beyond
我们研究费米跃迁和同位旋混合同位素链70-78 Kr考虑各种近似，使用相同的Skyrme-Hartree-Fock单粒子基础。我们研究库仑效应以及BCS和准粒子无规相近似（QRPA）关联的效果。本文用N=Z核（推广到N不同于Z核）的同位旋算符平方的期望值定义了近似基态的同位旋混合测度。从严格的Hartree-Fock方法出发，在不考虑库仑的情况下，证明了同位旋破缺是可以忽略的，当（N-Z）=6时为千分之几，当考虑库仑时为百分之几。配对关联诱导了相当大的同位旋混合和禁戒型费米跃迁（N<Z时为β-，N>Z时为β +）。BCS关联产生的增强在很大程度上被QRPA关联所补偿，QRPA关联由倾向于恢复同位旋对称性的同位旋守恒残余相互作用引起。
The asymptotic time derivative of the total dipole signal is proposed as an useful observable to investigate on Isospin equilibration phenomenon in multi-fragmentation processes. The study has been developed to describe charge/mass equilibration processes involving the gas and liquid "phases" of the total system formed during the early stage of a collision. General properties of this observable and the links with others isospin dependent phenomena are discussed. In particular, the $^{40}Cl+^{28}Si$ system at 40 MeV/nucleon is investigated by means of semiclassical microscopic many-body calcula…
Isospin mixing, Fermi transitions and signatures of nuclear deformation within a mean field approach
在HF+BCS+pnQRPA理论框架下考虑Gamow-Teller和Fermi跃迁。我们在这里展示了如何Gamow-Teller强度分布可以用于寻找中子缺陷Pb，Hg和Po同位素中的核变形的签名，以及费米跃迁如何使我们能够量化N=Z周围的一些甚至Kr同位素中的同位旋混合。
Isospin-mixing corrections for fp-shell Fermi transitions
在壳层模型的框架下计算了{ \it fp}壳层核超允许费米跃迁的同位旋混合修正。这项研究包括三个原子核，它们是九个精确测量的跃迁中的一部分，以及五个预计将在未来在放射性束设施中测量的案例。我们还包括一些新的计算$^{10}$ C。通过对9个精确测量的$ft$值进行同位旋混合修正，验证了守恒矢量流假设和Cabbibo-Kobayashi-Maskawa（CKM）矩阵的么正性条件。
Isospin Dynamics in Peripheral Heavy Ion Collisions at Fermi Energies
本文详细研究了费米能区周边碰撞中的同位旋动力学。我们考虑在35和50 AMeV的（124，112）Sn同位素的对称和混合碰撞，以研究不同反应组分（残留物，气体和可能的中间质量碎片）之间的同位旋输运，特别是在混合系统中的电荷平衡。我们评估的漂移项的影响，由于不对称性和密度梯度，这是直接相关的鲜为人知的值和斜率的对称性能量低于饱和密度。我们验证了一个isoscillatory动量依赖的平均场，这是发现影响的同位旋输运，因为它改变了反应时间的重要性。最后，我们提出了两个观测值特别敏感的核物质状态方程的等矢量部分：同位旋平衡和动能损失的二元事件之间的相关性，和颈部碎裂事件产生的中快度碎片的同位旋含量。
Isospin Dynamics in Heavy Ion Collisions: EoS-sensitive Observables
重离子碰撞（HIC）是研究非饱和区和高核子动量区介质内核相互作用的独特工具。在这份报告中，我们提出了一个选择的反应观测特别敏感的相互作用的矢量的一部分，即对称项的核物质状态方程（EoS）在低能量的行为的对称能量饱和周围的影响耗散和碎片产生机制。预测显示深非弹性和碎裂碰撞引起的中子丰富的弹丸。差分流量测量也将揭示有争议的中子/质子有效质量分裂不对称的物质。高密度对称项可以从相对论能量（几个AGeV范围）重离子反应的同位旋效应中推导出来，这甚至可以允许对强子介质中等矢量相互作用的协变结构进行“直接”研究。相当敏感的观测建议从集体流动和π/K介子生产。最后提出了在重子和同位旋密度较高时，向强子-夸克混合相跃迁的可能性。一些特征可能来自预期的“中子俘获”效应。
Prompted by the level of accuracy now being achieved in tests of the unitarity of the CKM matrix, we consider the possible modification of the Fermi matrix element for the $β$-decay of a neutron, including possible in-medium and isospin violating corrections. While the nuclear modifications lead to very small corrections once the Behrends-Sirlin-Ademollo-Gatto theorem is respected, the effect of the $u-d$ mass difference on the conclusion concerning $V_{ud}$ is no longer insignificant. Indeed, we suggest that the correction to the value of $|V_{ud}|^2 \, + \, |V_{us}|^2 \, + \, |V_{ub}|^2$ is …
We propose a few selected experimental approaches to show that new-generation instruments can give a direct access to significant observables on the density dependence of the symmetry energy in the nuclear equation of state. The form of such dependence is investigated within the Stochastic Mean Field model, coupled to a secondary-decay treatment.
Isospin Distillation with Radial Flow: a Test of the Nuclear Symmetry Energy
我们讨论了费米能区丰中子系统中心碰撞中的同位旋输运机制。在随机输运理论的框架下，对两组分体系中的同位旋蒸馏和膨胀动力学进行了完全自洽的研究。我们分析了碎片观测值之间的相关性，重点研究碎片的平均N/Z，作为其动能的函数。我们确定了这些观测值之间的EOS依赖关系，允许更好地表征的碎裂路径，并获得新的信息的对称性能量的低密度行为。
The asymptotic time derivative of the total dipole signal is proposed as an useful observable to study Isospin equilibration phenomenon in multi-fragmentation processes. The study proceeds through the investigation of the $^{40}Cl+^{28}Si$ system at 40 MeV/nucleon by means of semiclassical microscopic many-body calculations based on the CoMD-II model. In particular, the study has been developed to describe charge/mass equilibration processes involving the gas and liquid "phases" of the total system formed during the early stage of a collision. Through the investigation of dynamical many-body c…
Within the framework of ImQMD05, we study several isospin sensitive observables, such as DR(n/p) ratios, isospin transport ratio (isospin diffusion), yield ratios for LCPs between the projectile region and mid-rapidity region for the reaction systems Ni+Ni, Zn+Zn, Sn+Sn at low-intermediate energies. Our results show that those observables are sensitive to the density dependence of symmetry energy, and also depend on the cluster formation mechanism. By comparing these calculations to the data, the information of the symmetry energy and reaction mechanism is obtained.
Within two different frameworks of isospin-dependent transport model, i.e., Boltzmann-Uehling-Uhlenbeck (IBUU04) and Ultrarelativistic Quantum Molecular Dynamics (UrQMD) transport models, sensitive probes of nuclear symmetry energy are simulated and compared. It is shown that neutron to proton ratio of free nucleons, pi-/pi+ ratio as well as isospin-sensitive transverse and elliptic flows given by the two transport models with their "best settings", all have obvious differences. Discrepancy of numerical value of isospin-sensitive n/p ratio of free nucleon from the two models mainly originates …
Influence of a momentum dependent interaction on the isospin dependence of fragmentation and dissipation in intermediate energy heavy ion collisions
利用一个与同位旋相关的量子分子动力学模型，研究了在中能重离子碰撞中，同位旋效应下动量相关相互作用对碎裂和耗散的影响.结果表明，在动量相关相互作用下，核的阻止、发射的核子数和中等质量碎片的多重性都比没有动量相关相互作用时大。特别是，这些可观测量的差异，当使用一个同位旋相关的介质中核子核子截面与一个同位旋独立的，也是更大的动量相关的相互作用在高能量比没有一个。因此，动量依赖性增强了这些观测量对介质中核子核子截面的高能量同位旋效应的敏感性
Based on the Isospin-dependent transport model Boltzmann-Uehling-Uhlenbeck (IBUU), effects of the high momentum tail (HMT) of nucleon momentum distribution in colliding nuclei on some isospin-sensitive observables are studied in the semi-central $^{197}\rm {Au}+^{197}\rm {Au}$ reactions at incident beam energy of 400 MeV/nucleon. It is found that the nucleon transverse flow, the difference of neutron and proton transverse flows, the nucleon elliptic flow and free neutron to proton ratio are all less sensitive to the HMT, while the isospin-sensitive nucleon elliptic flow difference is clearly a…
Within the framework of the Lanzhou quantum molecular dynamics (LQMD) transport model, the isospin effect in peripheral heavy-ion collisions has been investigated thoroughly. A coalescence approach is used for recognizing the primary fragments formed in nucleus-nucleus collisions. The secondary decay process of the fragments is described by the statistical code, GEMINI. Production mechanism and isospin effect of the projectile-like and target-like fragments are analyzed with the combined approach. It is found that the isospin migration from the high-isospin density to the low-density matter ta…
This paper focuses on two problems. The first is related to the consistency checks of the complete correlation coefficients between two groups of variables obtained in Phys. Lett. B 749, 262 (2015). The first group collects parameters that describe properties of nuclear matter referring to the transport model involved. The second one is a group of observables adopted in the heavy ion collision experiments. The second problem concerns the method of determining the values of pure correlations between some variables in heavy ion collision. The application of this method for the analysis of the co…
Isospin fractionation : equilibrium versus spinodal decomposition
本文利用Skyrme有效相互作用，用平均场方法研究了非对称核物质液-气相变的同位旋性质。我们比较了两种不同的机制相分离的低密度物质：平衡和调幅分解。从自由能曲率推导出的相位，其中包含的平均同位旋含量和系统的波动信息的同位旋属性。一些实验上可获得的同位旋观测的影响。
Self-consistent random phase approximation (RPA) approaches in the relativistic framework are applied to calculate the isospin symmetry-breaking corrections $δ_c$ for the $0^+\to0^+$ superallowed transitions. It is found that the corrections $δ_c$ are sensitive to the proper treatments of the Coulomb mean field, but not so much to specific effective interactions. With these corrections $δ_c$, the nucleus-independent $\mathcal{F}t$ values are obtained in combination with the experimental $ft$ values in the most recent survey and the improved radiative corrections. It is found that the constancy…
Isospin in Reaction Dynamics. The Case of Dissipative Collisions at Fermi Energies
不稳定核物理中的一个关键问题是对非对称核物质（$ANM$）的$EOS$的认识。低密度区的对称能对中子皮结构有重要影响，而高密度区的对称能对超新星动力学和中子星性质有重要影响。$only$在地球实验室中探测等矢量$EOS$的这种区域的方法是通过从低能量到相对论能量的非对称（直到奇异）重离子的非常耗散的碰撞。本文首先对这一课题作了一个概述。然后，我们通过详细讨论的$neck-fragmentation$过程作为主要的耗散机制在费米能量和相关的同位旋动力学。从随机平均场模拟的所有阶段的反应动力学的同位旋效应进行了彻底的分析，从快速核子发射到中快碎片的形成，直到动态裂变的$spectator$残留物。模拟已经进行了增加刚度的对称项的$EOS$。已经注意到一些差异，特别是对于碎片电荷不对称性。从碎片不对称性与冻结时动力学量的关联中揭示了新的同位旋效应。最后列出了一系列有待进一步测量的同位旋敏感观测量。
High energy Heavy Ion Collisions (HIC) are studied in order to access nuclear matter properties at high density. Particular attention is paid to the selection of observables sensitive to the poorly known symmetry energy at high baryon density, of large fundamental interest, even for the astrophysics implications. Using fully consistent transport simulations built on effective theories we test isospin observables ranging from nucleon/cluster emissions to collective flows (in particular the elliptic, squeeze out, part). The effects of the competition between stiffness and momentum dependence of …
We review recent results obtained for charge asymmetric systems at Fermi and intermediate energies, ranging from 30 MeV/u to 1 GeV/u. Observables sensitive to the isospin dependent part of nuclear interaction are discussed, providing information on the symmetry energy behavior from sub- to supra-saturation densities.
We investigate the radial-overlap part of the isospin-symmetry breaking correction to superallowed $0^+\to 0^+$-decay using the shell-model approach similar to that of Refs. [1, 2]. The 8 sd-shell emitters with masses between $A=22$ and $A=38$ have been re-examined. The Fermi matrix element is evaluated with realistic spherical single-particle wave functions, obtained from spherical Woods-Saxon (WS) or Hartree-Fock (HF) potentials, fine-tuned to reproduce the experimental data on charge radii and separation energies for nuclei of interest. The elaborated adjustment procedure removes any sensit…
Background: The superallowed beta-decay rates provide stringent constraints on physics beyond the Standard Model of particle physics. To extract crucial information about the electroweak force, small isospin-breaking corrections to the Fermi matrix element of superallowed transitions must be applied. Purpose: We perform systematic calculations of isospin-breaking corrections to superallowed beta-decays and estimate theoretical uncertainties related to the basis truncation, time-odd polarization effects related to the intrinsic symmetry of the underlying Slater determinants, and to the function…
Within a transport model using as the input nucleon momentum profiles from a parameterized isospin-dependent single-nucleon momentum distribution with a high momentum tail induced by short-range correlations, we employ the $^{197}$Au + $^{197}$Au collisions at 400 MeV/nucleon to examine on one hand effects of the short-range correlations on the pion and flow observables in probing the nuclear symmetry energy, and on the other hand how reliable are this isospin-dependent single-nucleon momentum distribution as well as the corresponding parameter settings. Besides significant effects of the shor…
We study the shell-model formalism to include the isospin-symmetry-breaking correction ($δ_{C}$) to nuclear matrix element of superallowed $0^+\to 0^+$ Fermi $β$ decays of $T=1$ nuclei. Based on a perturbation expansion in a small quantity, such as the deviation of the overlap integral between proton and neutron radial wave functions from unity or of the transition density from its isospin-symmetry value, we derive that $δ_C$ can be obtained as a sum of six terms, including two leading order (LO) terms, two next-to-leading order (NLO) terms, one next-to-next-to-leading order (NNLO) term and on…
We explore the influence of in-medium nucleon-nucleon cross section, symmetry potential and impact parameter on isospin sensitive observables in intermediate-energy heavy-ion collisions with the ImQMD05 code, a modified version of Quantum Molecular Dynamics model. At incident velocities above the Fermi velocity, we find that the density dependence of symmetry potential plays a more important role on the double neutron to proton ratio $DR(n/p)$ and the isospin transport ratio $R_i$ than the in-medium nucleon-nucleon cross sections, provided that the latter are constrained to a fixed total NN co…
Observable effects of symmetry energy in heavy-ion collisions at RIA energies
在丰中子核诱导核反应的同位旋相关输运模型中，我们对束流能量为30 MeV/A和400 MeV/A的$^{100}Sn+^{124}Sn$和$^{100}Zn+^{124}Sn$反应进行了比较研究，以确定最佳的实验条件和观测值，用于研究富中子物质的物态方程。几个观测已知是敏感的对称性能量的密度依赖性检查作为碰撞参量的函数为两个反应系统。特别地，利用自由核子的快度分布和它们的同位旋不对称性研究了同位旋输运/扩散的强度。即使对于对称能量为30 MeV/A的非常软的周边碰撞，也建立了近似的同位旋平衡。然而，在400 MeV/A，即使在大多数中心碰撞中，无论是软对称能量还是硬对称能量，都观察到强的同位旋不透明性。这些意见的起源和它们的影响，以确定在稀有同位素加速器（RIA）的丰中子物质的状态方程进行了讨论。
Based on an exact formalism, we study the effects of isospin-symmetry-breaking interactions on superallowed 0+ -> 0+ transitions. We calculate the second-order renormalization of the Fermi matrix element due to radial contributions and show that radial excitations neglected in the treatment of Towner and Hardy are significant. These are estimated to decrease the isospin-symmetry-breaking corrections. Our results provide a correction term that can be included in existing approaches.
Effects of isospin-symmetry violation on tests of the standard model using parity-violating electron scattering
在核壳层模型的框架下，研究了12 C、16 O和28 Si的同位旋对称性破缺对宇称破坏电子散射观测值的影响。贡献由于混合与低洼状态以及混合物的1 p-1h配置（通过径向波函数）占。它被发现，同位旋混合可以是重要的，和后果有关的精确测试的标准模型得到解决。
For the A=32 T=2 quintet we provide a unified theoretical description for three related aspects of isospin mixing: the necessity of more than three terms in the isobaric mass multiplet equation, isospin-forbidden proton decay, and a correction to the allowed Fermi beta decay. We demonstrate for the first time that all three effects observed in experiment can be traced to a common origin related to isospin mixing of the T=2 states with T=1 states.
A precision measurement of the gamma yields following the beta decay of 32Cl has determined its isobaric analogue branch to be (22.47^{+0.21}_{-0.19})%. Since it is an almost pure Fermi decay, we can also determine the amount of isospin-symmetry breaking in this superallowed transition. We find a very large value, delta_C=5.3(9)%, in agreement with a shell-model calculation. This result sets a benchmark for isospin-symmetry-breaking calculations and lends support for similarly-calculated, yet smaller, corrections that are currently applied to 0+ -> 0+ transitions for tests of the Standard Mode…
On the Fermi and Gamow-Teller strength distribution in medium-heavy mass nuclei
基于连续随机相位近似（CRPA）的同位旋自洽方法被应用于描述费米和Gamow-Teller强度分布在一个宽的激发能间隔。为了考虑开壳层核中的核子配对，我们将BCS模型引入到CRPA方法中，建立了一个同位旋自洽的质子-中子-准粒子CRPA（pn-QCRPA）方法。分析了单开壳层核中伽莫夫-特勒巨共振的同位旋和组态分裂。对$^{208}$ Bi、$^{90}$ Nb和Sb同位素的计算结果与实验数据进行了比较。
Constraining the Symmetry Energy: A Journey in the Isospin Physics from Coulomb Barrier to Deconfinement
重离子碰撞（HIC）是探测非饱和区介质内核相互作用的一种独特工具。在这项工作中，我们提出了一个选择的反应观测耗散碰撞特别敏感的相互作用的矢量部分，即对称项的核物质状态方程（EoS）。在低能量下，饱和周围的对称能的行为影响耗散和碎片产生机制。我们将首先讨论最近观察到的动态偶极辐射，由于集体中子质子振荡期间的电荷平衡在聚变和深非弹性碰撞。强调重要的Iso-EOS效应。由不稳定的132 Sn束引起的反应似乎是非常有前途的工具来测试欠饱和Isovector EoS。新的同位旋敏感的观测值也提出了深非弹性，碎裂碰撞和同位旋平衡测量（不平衡比）。高密度对称项可以从相对论能量（几个AGeV范围）重离子反应的同位旋效应中推导出来，这甚至可以允许对强子介质中等矢量相互作用的协变结构进行“直接”研究。相当敏感的观测建议从集体流动和π/K介子生产。最后提出了在重子和同位旋密度较高时，向强子-夸克混合相跃迁的可能性。一些特征可能来自预期的“中子俘获”效应。最后强调了研究从低能到相对论能的放射性核束猛烈碰撞的重要性。
Isospin-symmetry-breaking corrections to superallowed Fermi beta decay: Formalism and schematic models
研究了从超允许0+ -> 0+核β衰变中提取上下Cabibbo-Kobayashi-Maskawa矩阵元时包含同位旋对称性破缺修正的形式.我们表明，有没有一阶同位旋对称性破缺相关的核矩阵元的修正。我们发现纠正唐纳和哈代的治疗，并评估这些使用日益复杂的示意图模型。
The density-dependent nuclear symmetry energy is directly related to the isospin asymmetry for finite and infinite nuclear systems. It is critical to determine the coefficients of symmetry energy and its related observables as it holds great importance in different areas of nuclear physics, such as analyzing the structure of ground state exotic nuclei and neutron star study. The ground state bulk properties such as nuclear binding energy, quadrupole deformation, two-neutron separation energy, the differential variation of two-neutron separation energy, and root-mean-square charge radius for Sc…
In the framework of mean-field based transport approaches, we discuss recent results concerning heavy ion reactions between charge asymmetric systems, from low up to intermediate energies. We focus on isospin sensitive observables, aiming at extracting information on the density dependence of the isovector part of the nuclear effective interaction and of the nuclear symmetry energy. For reactions close to the Coulomb barrier, we explore the structure of collective dipole oscillations, rather sensitive to the low-density behavior of the symmetry energy. In the Fermi energy regime, we investigat…
Long Range Tensor Correlations in Charge and Parity Projected Fermionic Molecular Dynamics
在费米子分子动力学的框架内，发展了一种方法，当用单个斯莱特行列式时，可以更好地解释原子核中的长程张量关联。具有混合的同位旋和破宇称的单粒子态建立了一个内在的斯莱特行列式，然后将其投影到电荷和宇称上。通过最小化这个多体状态的能量相对于单粒子状态的参数和投影后的角动量基态能量得到系统地低于相应的Hartree-Fock结果。采用真实的Argonne V18势，用酉相关算子方法处理短程关联。与精确的少体计算的比较表明，在$^4$他约五分之一的相关能量，由于长程相关占。这些相关性延伸到整个原子核，用内禀态的同位旋和自旋-同位旋密度来表示。自旋-同位旋密度的发散是π介子场的来源，它具有偶极性质。
Density dependence of isospin observables in spinodal decomposition
同位素的碎片形成的波动进行了研究的准解析描述的旋节线分解方案。利用涨落-耗散关系，导出了在给定密度、电荷不对称性、温度和系统在不稳定区所花时间下，密度涨落协方差矩阵随核物质波矢的变化关系。然后，在普通空间中的密度波动与有限立方晶格中进行的傅立叶变换来实现。在这个盒子里，不同密度的区域共存，最终形成核子簇。在我们的方法中，同位素分布由领先的不稳定isoscalarlike模式的N/Z比和isovectorlike波动存在于正在进行的旋节分解的物质确定。因此，团簇N/Z比的平均值和相对分布的宽度反映了对称能的性质。产生大量的事件，这些计算允许仔细调查的群集同位素含量作为群集密度的函数。平均电荷不对称性和同位素分布的宽度随着密度的增加而均匀减小。最后，我们注意到，结果基本上是指系统的早期破裂。
Spin and Isospin Effects in the NN -> NK Lambda Reaction Near Threshold
本文分析了核子-核子碰撞中K ~+ λ产生在近阈区的振幅和观测量的自旋和同位旋结构。结果表明，合理的值的π和ρ项的相对强度在介子交换模型中，预计生产的中子显着强于质子。由于π-ρ干涉，自旋转移系数D_NN也被预测为负值。
The validity of impact parameter estimation from the multiplicity of charged particles at low-intermediate energies is checked within the framework of ImQMD model. The simulations show that the multiplicity of charged particles cannot estimate the impact parameter of heavy ion collisions very well, especially for central collisions at the beam energies lower than $\sim$70 MeV/u due to the large fluctuations of the multiplicity of charged particles. The simulation results for the central collisions defined by the charged particle multiplicity are compared to those by using impact parameter b=2 …
IMF isotopic properties in semi-peripheral collisions at Fermi energies
本文研究了47 AMeV半周边碰撞中中子和质子沿碎裂路径的动力学行为：58 Fe +58 Fe（电荷不对称，N/Z = 1.23）和58 Ni +58 Ni（电荷对称，N/Z = 1.07）。我们观察到在电荷对称的58 Ni +58 Ni系统中也发生了同位旋动力学过程，这可能产生更多的非对称碎片。观察到颈部碎片的中子富集，这是由于平衡前发射和“同位旋迁移”现象之间的相互作用。这两种效应都依赖于状态方程（EoS）对称项。这一点是通过比较两种不同选择的对称性能量密度依赖性所获得的结果来说明的。提出了新的关联观测量，用以研究反应机理和同位旋动力学。
The isospin diffusion of the quasi-projectile formed in the $^{64,58}Ni$ on $^{64,58}Ni$ reactions in the Fermi energy domain is investigated in the framework of the Boltzmann-Uehling-Uhlenbeck transport model. The well known isospin transport ratio observable is revisited, with the aim of insuring an optimal comparison between experimental data and theoretical calculations and reducing the present uncertainties in the extraction of empirical equation of state parameters. We show that isospin transport ratios are sensitive to all the low order isovector parameters ($E_{sym}$, $L_{sym}$ and $K_…
Investigation of observables from nuclear multifragmentation reactions depending on isospin led to the development of a hybrid model. The mass and charge distribution as well as isotopic distribution was studied using this model for $^{112}$Sn+$^{112}$Sn reaction as well as $^{124}$Sn+$^{124}$Sn reactions at different energies. The agreement of the results obtained from the model with those from experimental data confirms the accuracy of the model. Isoscaling coefficients were extracted from these observables which can throw light on the symmetry energy coefficient. Another important facet of …
Nucleon-Nucleon Scattering Observables in Large-$N_c$ QCD
在QCD的大$N_c$极限下，考虑了核子-核子散射观测量，即具有中等高动量的初态（$p \sim N_c$）。在含时平均场近似的框架下研究了散射。我们着重于这些观测值的自旋和同位旋的初始状态，可以使用含时平均场论理论计算的依赖。我们证明了，在修正之前，所有这些观测量在自旋和同位旋同时翻转下必须是不变的（{ \it，即}通过$π/2$的自旋和同位旋旋转）作用于任一粒子。从自旋非极化测量中获得的这类观测值在达到$1/N_c$修正之前必须是与同位旋无关的。此外，可以表明，领先的校正是相对阶数$1/N_c^2$，而不是$1/N_c$。
Isospin effects on rotational flow in intermediate energy heavy ion collisions
在同位旋相关的量子分子动力学模型框架下，通过分析不同碰撞参量下40 MeV/核子的$^{58}$ Fe + $^{58}$ Fe和$^{58}$ % Ni + $^{58}$ Ni反应的中快度角分布，研究了反应中的旋转流.转动观测量也进行了半定量计算。首次发现富中子系统（$^{58}$ Fe + $^{58}$ Fe）具有更强的旋转集体流。这种旋转集体流的同位旋依赖性在半周边碰撞中更为明显，它主要是由核子-核子截面的同位旋依赖性引起的，而不是由对称能引起的.同时指出，旋转流动强烈地依赖于碰撞参量。
Based on the ultra-relativistic quantum molecular dynamics (UrQMD) model, the impacts of momentum dependent interaction, symmetry energy and near-threshold $NN\to NΔ$ cross sections on isospin sensitive collective flow and pion observables are investigated. Our results confirm that the elliptic flow of neutrons and charged particles, i.e. $v_2^n$ and $v_2^{ch}$, are sensitive to the strength of momentum dependence interaction and the elliptic flow ratio, i.e., $v_2^n/v_2^{ch}$, is sensitive to the stiffness of symmetry energy. For describing the pion multiplicity near the threshold energy, acc…
Isospin relaxation time in heavy-ion collisions at intermediate energies
利用一个与同位旋相关的输运模型，研究了中能重离子碰撞中重残留物的同位旋和动量弛豫时间。结果表明，只有在入射能量低于费米能时，才能达到化学平衡或热平衡，然后才能在重剩余物中发展出动力学不稳定性。在束流能量低于（高于）费米能时，同位旋弛豫时间比动量弛豫时间短（长）。
Isospin Dynamics in Heavy Ion Collisions: from Coulomb Barrier to Quark Gluon Plasma
重离子碰撞（HIC）是探测非饱和区介质内核相互作用的一种独特工具。在这份报告中，我们提出了一个新的反应观测值的选择耗散碰撞特别敏感的对称项的核物质状态方程（Iso-EoS）。我们将首先讨论同位旋平衡动力学。在低能量下，这通过最近观察到的动态偶极辐射表现出来，这是由于集体中子-质子振荡的对称项作为回复力。在更高的射束能量下，将在不平衡比测量中看到Iso-EoS效应，特别是从与总动能损失的相关性中。对于中心事件中的碎裂反应，我们建议考虑同位旋蒸馏和径向流之间的耦合。在颈部碎裂反应中，从同位旋含量和碎裂之间的相关性可以获得重要的$Iso-EoS$信息。高密度对称项可以从相对论能量（几个AGeV范围）的重离子反应的同位旋效应中探测到。相反，同位旋敏感的观测建议从核子/集团排放，集体流和介子的生产。还提出了揭示有争议的中子/质子有效质量分裂在不对称物质的可能性。在重子密度较高时，大的对称性排斥也将导致富n物质中强子-解禁闭跃迁的“提前”。一个合适的治疗的isovector相互作用的部分电子EoS出现非常相关的。
We discuss the isospin effect on the possible phase transition from hadronic to quark matter at high baryon density and finite temperatures. The two-Equation of State (Two-EoS) model is adopted to describe the hadron-quark phase transition in dense matter formed in heavy-ion collisions. For the hadron sector we use Relativistic Mean Field (RMF) effective models, already tested on heavy ion collision (HIC). For the quark phase we consider various effective models, the MIT-Bag static picture, the Nambu--Jona-Lasinio (NJL) approach with chiral dynamics and finally the NJL coupled to the Polyakov-…
An investigation of the isospin equilibration process in the reactions $^{58,64}$Ni+$^{58,64}$Ni at two bombarding energies in the Fermi regime ($32\,$MeV/nucleon and $52\,$MeV/nucleon) is presented. Data have been acquired during the first experimental campaign of the coupled INDRA-FAZIA apparatus in GANIL. Selecting from peripheral to semi-central collisions, both the neutron content of the quasiprojectile residue and that of the light ejectiles coming from the quasiprojectile evaporation have been used as probes of the dynamical process of isospin diffusion between projectile and target for…
Isospin symmetry is explicitly broken in the Standard Model by the non-zero differences of mass and electric charge between the up and down quarks. Both of these corrections are expected to have a comparable size of the order of one percent relatively to hadronic energies. Although these contributions are small, they play a crucial role in hadronic and nuclear physics. In this review we explain how to properly define QCD and QED on a finite and discrete space-time so that isospin corrections to hadronic observables can be computed ab-initio. We then consider the different approaches to compute…
The symmetry energy in the nuclear equation of state affects many aspects of nuclear astrophysics, nuclear structure, and nuclear reactions. Recent constraints from heavy ion collisions, including isospin diffusion observables, have started to put constraints on the symmetry energy below nuclear saturation density, but these constraints depend on the employed transport model and input physics other than the symmetry energy. To understand these dependencies, we study the influence of the symmetry energy, isoscaler mean field compressibility and momentum dependence, in-medium nucleon-nucleon cro…
A Skyrme-type momentum-dependent nucleon-nucleon force distinguishing isospin effect is parameterized and further implemented in the Lanzhou Quantum Molecular Dynamics (LQMD) model for the first time, which leads to a splitting of nucleon effective mass in nuclear matter. Based on the isospin- and momentum-dependent transport model, we investigate the influence of momentum-dependent symmetry potential on several isospin-sensitive observables in heavy-ion collisions. It is found that symmetry potentials with and without the momentum dependence but corresponding to the same density dependence of…
Isospin Effects on Meson Production in Relativistic Heavy Ion Collisions
我们表明，在中等能量（几个AGeV范围）的重离子反应的同位旋效应的现象是非常丰富的，可以允许一个“直接”的协变结构的研究在高密度强子介质中的等矢量相互作用。我们的工作在一个相对论性的运输框架内，超越级联图片，一贯来自有效的拉格朗日，其中同位旋效应占平均场和碰撞条款。我们发现，π/K介子产生（π^-/π^+，K^0/K^+产额）提供了相当敏感的观测值。强调了相关的非平衡效应。最后提出了在重子和同位旋密度较高时，向强子-夸克混合相跃迁的可能性。一些特征可能来自预期的“中子俘获”效应。
Heavy Ion Collisions at Relativistic Energies: Testing a Nuclear Matter at High Baryon and Isospin Density
我们表明，在中等能量（几个AGeV范围）的重离子反应的同位旋效应的现象是非常丰富的，可以允许一个“直接”的协变结构的研究在强子介质中的等矢量相互作用。我们的工作在一个相对论性的运输框架内，超越级联图片，一贯来自有效的拉格朗日，其中同位旋效应占平均场和碰撞条款。从集体流（"差分“流）和π/K介子产生（$π^-/π^+$，$K^0/K^+$产量）提出了相当敏感的可观测量。对于后一点，强调相关的非平衡效应。最后提出了在重子和同位旋密度较高时，向强子-夸克混合相跃迁的可能性。一些特征可能来自预期的“中子俘获”效应。
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