部分子末态的色分离联接对e+e－反应中强子产额及其动量谱的影响

用JETSET事例产生器对e⁺e^－→qq+ng→hadrons反应中,末态部分子(qq+ng)以色分离的联接方式进行强子化时,各种强子产额及π⁺,K^±,p/p的动量谱进行了计算;与传统的色中性流联接方式强子化结果进行比较.结果表明:由T权重确定的色分离单态和色中性流这两种完全不同的色联接方式强子化得到的强子产额及π⁺,K^±,p/p的动量谱,与实验符合的程度相同,有些更好.     

LUND面积定律产生子在R值测量中的应用

对Lund弦碎裂模型强子化面积定律严格求解,得到e⁺e^－湮没产生少体初始强子态的遍举分布.基于面积定律的新产生子LUARLW在2—5GeV能区的模拟结果与BES数据的多种谱分布符合很好,用于BES上强子产生总截面测量的强子探测效率的估计.     

不同快度窗口中带电多重数的奇、偶分布及归一化矩的能量依赖性

本文从一个简单的具有非零电荷关联长度的物理图象出发,计算了强子-强子碰撞在不同快度窗口中的奇、偶带电多重数分布,解释了这些分布的重合和分开.计算得到的规一化矩的窗口依赖性和能量依赖性与实验一致.引进了一种新的、特别适合于小快度窗口的归一化矩.     

不同快度窗口中带电多重数的奇、偶分布及归一化矩的能量依赖性

本文从一个简单的具有非零电荷关联长度的物理图象出发,计算了强子-强子碰撞在不同快度窗口中的奇、偶带电多重数分布,解释了这些分布的重合和分开.计算得到的规一化矩的窗口依赖性和能量依赖性与实验一致.引进了一种新的、特别适合于小快度窗口的归一化矩.     

高能电子–正电子碰撞产生的喷注内部分形性质的蒙特–卡洛研究

用蒙特–卡洛方法研究了91.2GeV e⁺e^－碰撞产生的喷注内部的分形性质.采用一个新变量r得到了很好的反常标度性.研究了不同阶标度指数之间的关系,得到了喷注内部强子系统的Lévy指数,并和电子–正电子碰撞及强子–强子碰撞的相应指数作了对比.讨论了结果的意义.     

强子-强子核相互作用参数化模型在超高能宇宙线研究中的应用

在混合初级宇宙线成分的假定下,用参数化模型描述强子-强子相互作用过程,模拟超高能宇宙线粒子在大气中的行为,并将模拟计算结果同高山乳胶室的实验数据进行了细致的比较与讨论.同时详细讨论了碎裂区次级粒子平均横动量取值对模拟计算结果的影响.     

超高能软强子作用的Chou–Yang模型

用Chou-Yang模型构造了一个用于s=26GeV到22TeV的软强子非单衍相互作用MonteCarlo产生器.结合大横动量喷注产生过程的pQCD计算和相应的部分子强子化方案,较好地再现了高能区实验的结果.平滑地外推到超高能区,预言了非弹性度随能量下降的趋势.     

BSW方案中的模型相关性

在Baner,Stech,Wirbel(BSW)方案中,计算D和B介子弱衰变矩阵元使用了强子模型波函数.分析了几种不同的价夸克模型波函数,研究了它们的性质,正确地应用于计算D和B介子弱衰变过程的分支比.结果表明,在目前的实验误差范围内对于不同的模型波函数,相应地选取合适的a₁和a₂参量都能得到与大多数实验数据相符的预言.因此从理论上进一步探讨弱过程因子化,强子波函数和从实验上提高精度都将有助于研究BSW方案的模型相关性和可靠性.     

强子-强子核相互作用的参数化模型

对ISR和SppS非弹过程赝快度分布的实验数据进行最佳参数拟合直至其最高能量S=900GeV,假定次级粒子多重数分布近似遵循KNO Scaling,横动量近似遵循指数分布,构造了一个适合于分析乳胶室实验结果的强子-强子核相互作用的参数化模型.     

强子质量谱的变分研究

本文在格点QCD范围用线性变分法计算了强子质量谱及其波函数, 在中间耦合区域得到了合理的结果.     

The effect of hadronization on the instabilities in an expanding parton plasma

The growth rate for instabilities in an expanding parton plasma is investigated by using a quasiparticle transport model including hadronization. The coupled Boltzmann equations for partons and pions with time dependent mean field masses and source terms are solved in the Bjorken boost invariant picture. Hadronization modifies the known instability in the parton plasma created by the mean field in two ways: In the beginning, hadronization increases the rate Γ of instability, but then Γ→ 0 when the hadronization is dominating the time evolution. Received: 11 January 1999     

Space-time evolution of hadronization

Beside its intrinsic interest for the insights it can give into color confinement, knowledge of the space-time evolution of hadronization is very important for correctly interpreting jet-quenching data in heavy-ion collisions and extracting the properties of the produced medium. On the experimental side, the cleanest environment to study the space-time evolution of hadronization is semi-inclusive deeply inelastic scattering on nuclear targets. On the theoretical side, two frameworks are presently competing to explain the observed attenuation of hadron production: quark energy loss (with hadron formation outside the nucleus) and nuclear absorption (with hadronization starting inside the nucleus). I will discuss recent observables and ideas which will help to distinguish these two mechanisms and to measure the time scales of the hadronization process. PACS 25.30.-c; 25.75.-q; 24.85.+p; 13.87.Fh     

Space-time evolution of hadronization in DIS: Semi-exclusive processes and grey track production

Semi-exclusive processes and grey track production in DIS off nuclear targets are analyzed as possible tools to investigate the space time evolution of hadronization.     

Atomic mass dependence of hadron production in semi-inclusive deep inelastic lepton-nucleus scattering

Hadron production in lepton-nucleus deep inelastic scattering is studied in a quark energy loss model. The leading-order computations for hadron multiplicity ratios are presented and compared with the selected HERMES pions production data with the quark hadronization occurring outside the nucleus by means of the hadron formation time. It is found that the obtained energy loss per unit length is 0.440 ± 0.013 GeV/fm for an outgoing quark by the global fit. It is confirmed that the atomic mass number dependence of hadron attenuation is theoretically and experimentally in good agreement with the A^2/3 power law for quark hadronization occurring outside the nucleus.     

Microscopic model for rapid hadronization of supercooled Quark-Gluon Plasma

A new hadronization scenario is proposed where a central role is played by the chiral symmetry break-down in the expanding Quark-Gluon Plasma. This mechanism becomes efficient after the thermal freeze-out of the quark-antiquark system. The transition from the chiral-symmetric to broken state proceeds through the formation of multi-quark-antiquark clusters which later on split into hadrons. This transition is accompanied by the formation of domains of long-lived coherent pion field (Disoriented Chiral Condensates). This picture can be observed through multi-hadron correlations and enhanced production of lowp _t pions. We estimate time scales and spatial characteristics of chiral-symmetry breaking instabilities on the basis of an effective field-theoretical model.     

Can we distinguish energy loss from hadron absorption?

Knowing whether a hadron is formed inside or outside the nuclear medium is very important for correctly interpreting jet quenching in heavy-ion collisions. The cleanest experimental environment to study the space-time evolution of hadronization is semi-inclusive DIS on nuclear targets. 2 frameworks are presently competing to explain the observed attenuation of hadron production: quark energy loss, with hadron formation outside the nucleus [2, 3], and nuclear absorption with hadronization starting inside the nucleus [4–6]. I demonstrate that the observed approximate A ^2/3 scaling of experimental data cannot conclusively establish the correctness of either energy loss or absorption.     

Hadronization from color interactions

A quark coalescence model, based on semi-relativistic molecular dynamics with color interactions among quarks, is presented and applied to pp collisions. A phenomenological potential with two tunable parameters is introduced to describe the color interactions between quarks and antiquarks. The interactions drive the process of hadronization that finally results in different color neutral clusters, which can be identified as hadrons based on some criteria. A Monte Carlo generator PYTHIA is used to generate quarks in the initial state of hadronization, and different values of tunable parameters are used to study the final state distributions and correlations. Baryon-to-meson ratio, transverse momentum spectra, pseudorapidity distributions and forward-backward multiplicity correlations of hadrons produced in the hadronization process, obtained from this model with different parameters, are compared with those from PYTHIA.     

Nonextensive boltzmann equation and hadronization

We present a novel nonextensive generalization of the Boltzmann equation. We investigate the evolution of the one-particle distribution in this framework. The stationary solution is exponential in a nonlinear function of the original energy. The total energy is composed using a general, associative nonextensive rule. We propose that for describing the hadronization of quark matter such rules may apply.     

Time-dependent formulation of the linear unitary transformation and the time evolution of general time-dependent quadratic Hamiltonian systems

A time-dependent closed-form formulation of the linear unitary transformation for harmonic-oscillator annihilation and creation operators is presented in the Schrödinger picture using the Lie algebraic approach. The time evolution of the quantum mechanical system described by a general time-dependent quadratic Hamiltonian is investigated by combining this formulation with the time evolution equation of the system. The analytic expressions of the evolution operator and propagator are found. The motion of a charged particle with variable mass in the time-dependent electric field is considered as an illustrative example of the formalism. The exact time evolution wave function starting from a Gaussian wave packet and the operator expectation values with respect to the complicated evolution wave function are obtained readily.     

Finite-Size Effects on the Phase Diagram and Evolution of Strangelets in Ultrarelativistic Heavy-Ion Collisions

In the framework of multiple reflection expansion, finite-size effects are incorporated into the study of the phase diagram and evolution of a strangelet in equilibrium with a finite hadronic phase. It is found that in a significant way finite-size effects can modify the phase diagram and reduce the survival probabilities of cold strangelets in ultrarelativistic heavy-ion collisions. The inclusion of finite-size effects can also allow a quantitative analysis of the properties of a cold strangelet resulting from a smooth hydrodynamic evolution with equilibrium hadronization and isentropic expansion.