干涉项对e+e－→qq+ng两种色连接几率的影响

传统高能e⁺e^－→hadrons事例产生器普遍采用大N_c近似,使色单态链产生几率达到100%而色分离态几率为0.本文在Nc=3的真实情况下,研究了干涉项中颜色部分和动量部分的来源及性质后发现,对e⁺e^－→qq+ng部分子末态中胶子数2,3,干涉项使色单态链产生几率进一步下降到67%,58%,而n=2时的色分离态几率则增大至不考虑干涉项的2倍.由上推断当胶子数n更大时色单态链几率将远小于1,色分离态几率将更显著增加.     

高能e+e－湮没三喷注事例的角度不对称性

利用部分子色相互作用形成色单态独立碎裂成末态强子的物理图像,系统计算了LEP能区e⁺e^－、q₀q₀ g→3jets事例带电粒子多重数,表明与事例拓扑结构有强烈的依赖性,计算结果与实验基本一致.     

对Z0三喷注事例中色联接敏感可观测量的研究

将末态部分子的色分离联接引入JETSET事例产生器,通过用喷注的DURHAM判据y_cut及用喷注夹角限制事例形状,对Z⁰衰变进行三喷注事例挑选,发现可以得到对色联接敏感的三喷注事例.对于这类事例,末态强子的平均带电多重数及胶子喷注中的一系列可观测量对色联接的敏感性随y_cut值的减小而增大;在小y_cut值时,色中性流和色分离两种联接导致了显著差别.使通过实验测量鉴别部分子的色联接成为可能.     

Technicolor模型下QCD对衰变B→Xτvτ的修正

在一代Technicolor模型下对内含的半轻子B衰变的()阶修正进行了计算. 将理论的预言与最近的实验结果比较,得到了荷电的色单态和色八重态赝标量粒子质量的下限:m_p>43GeV, M_P8>77GeV.     

e+e－→m(qq)+ng过程的颜色等效哈密顿量

Lund模型中多部分子的动量分布是由PQCD得出,而这些部分子间的色弦结构则另外由唯象模型指派.从最近发展的e⁺e^－→m(qq)+ng矩阵元递归形式,找出其颜色部分的等效哈密顿量H_c,研究了H_c矩阵元的基本性质,作为从PQCD统一研究多部分子间颜色组态及色相互作用的基础.     

四维杂化弦

利用十维N-S玻色弦和四维费米弦杂化,我们给出了四维杂化弦.其内部规范对称群为[SU(2)]⁶.它的基态包含有四维时空的超引力多重态及四维超杨-Mills规范多重态.四维杂化弦具有超对称、无快子态及洛仑兹不变等特性.     

玻色弦BRST形式的辛结构和量子化

本文用限制J′Y到它的拉格朗日子流形的方法给出玻色弦的辛结构并讨论BRST形式的几何量子化.我们可以看到,共形反常在G₀=G₀/H上的BRST真空丛的曲率为零时相消.     

两种色联接下的重子介子比及重子反重子关联

在e⁺e^－→h′s反应中,末态重子介子比及重子反重子关联,在流行的强子化模型中,仅有JETSET事件发生器能通过调节专用附加参数较好拟合实验,被认为是检验强子化模型的最敏感可观察量.用微扰QCD所允许的末态部分子100%的色分离联接,取代JETSET中大N_c近似下的色中性流联接,对这些可观察量作了预言.并与JETSET原有预言及最新实验结果作了比较.发现色分离联接同样甚至更好地与这些实验符合,这表明原来用色中性流联接与这些实验事实基本符合,并不意味着色中性流就是非微扰QCD选择的色联接方式,100%的色分离联接也是可能的.     

双色噪声激励下FHN神经元系统的稳态性质

应用统一色噪声理论研究了双色噪声激励下一维FitzHugh-Nagumo (FHN)神经元系统的动力学性质,即稳态概率分布函数和其平均值. 给出了FHN神经元系统的稳态概率密度和平均值的解析表达式. 结果表明: 乘性噪声的自关联时间τ ₁、加性噪声的自关联时间τ ₂、加性噪声强度α 和乘性噪声强度D都能够诱导非平衡相变的产生. α和D的增大有利于系统从激发态向静息态转换. τ₁, τ₂的增大有利于系统从静息态向激发态转换. 噪声强度和其自关联时间的作用完全相反.     

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.     

Probability of Color Singlet String States in e + e- → qq + ng at Large Nc Limit

We use the method of color effective Hamiltonian to calculate the probability of color singlet string states at the large N_c limit. We show that a qq + ng system produced from e + e^- annihilation is definitely in color singlet string states when N_c → ∞, i.e., color,singlet string states account for 100% of all possible color singlet states. This justifies the approximation that the hadronization mechanism of each color-neutral flow piece connecting two color-adjacent partons is assumed to be the same as an independent qq singlet system.     

干涉项对e~+e~-→q+ng两种色连接几率的影响

传统高能e+ e-→hadrons事例产生器普遍采用大Nc 近似 ,使色单态链产生几率达到 10 0 %而色分离态几率为 0 .本文在Nc=3的真实情况下 ,研究了干涉项中颜色部分和动量部分的来源及性质后发现 ,对e+ e-→qq +ng部分子末态中胶子数 2 ,3,干涉项使色单态链产生几率进一步下降到 6 7% ,5 8% ,而n =2时的色分离态几率则增大至不考虑干涉项的 2倍 .由上推断当胶子数n更大时色单态链几率将远小于 1,色分离态几率将更显著增加     

γ Radiative Decays to Light Quark Jets and Color Octet Mechanism

We study radiative decays of T to light quark jets in nonrelativistic QCD by taking both the color singlet and color octet b^-b operators into consideration. The cut for quark jet energy and cut for the angle between two quark jets are introduced. The sensitivity to the soft and collinear singularities in the loop integrals are greatly reduced by these cuts. With the jet energy cut of about 1 GeV, and the jet angle cut of about 36°, the branching ratio for γ→ rq^- is found to be 8.2 × 10^-4 from color singlet contributions. The color octet contributions could be much larger than that of color singlet, depending on the estimate of the color octet matrix elements. This process may provide a new test for the color octet mechanism in nonrelativistic QCD.     

Yang-Mills string theories

It is shown that the addition of a “colored” Yang-Mills supermultiplet to the locally supersymmetric spinning string Lagrangian does not yield a viable new string model, even though supersymmetry is preserved. However, a Yang-Mills extension of the Veneziano string that yields the color singlet sector of the Bardakçi-Halpern model is constructed.     

Influence of Interference Terms on Probability of Color Connections among Partons in e+e－→qq+ng Process

Large N_c approximation is adopted in popular e⁺e^－ event generators where the production probability of singlet chain states is 100% and that of color separate states is 0. In the real world N_c=3, we investigate the origin and character of color and kinematics aspects in interference terms. We find that the production probability of color singlet chain states decreases from 83%, 77% to 67%, 58% for qq+2g and qq+3g system respectively after considering the interference terms. Especially, the production probability of color separate states increases to twice of that without interference terms for qq+2g. Hence when n is larger, we can expect that the production probability of singlet chain states will be far less than 1 and that of color separate states will significantly increase when n is larger.     

Searching singlet extensions of the supersymmetric standard model in Z 6−II orbifold compactification of heterotic string

We search for supersymmetric standard model realizations with extra singlets and extra U(1) using the heterotic string compactification on the Z _6?II orbifold with two Wilson lines. The effective superpotential produced through the vacuum restabilization mechanism is examined for three representative Pati–Salam string models obtained in the literature. An automated selection of semi-realistic vacua along flat directions in the non-Abelian singlet modes field space is performed by requiring the presence of massless pairs of electroweak Higgs bosons having trilinear superpotential couplings with massless singlet modes and the decoupling of color triplet exotic modes needed to suppress B and L number violating processes.     

夸克的半经典输运方程

对夸克的量子输运方程取半径典近似时保留到Wigner函数的一次微商项;在色空间和自旋空间展开这个半经典输运方程,得到了色单态自旋标量和色单态自旋矢量的输运方程:并把得到的结果和阿贝尔等离子体进行比较讨论了QGP的非阿见尔性质.     

Inhomogeneous Shadowing Effect in High-Energy p-A Drell-Yan Process

Having studied the initial state energy loss versus nuclear shadowing for the Drell- Yan dimuon pair production in the color string model, the inhomogeneous shadowing effect is considered in this paper. We find that the inhomogeneous shadowing effect does amend the rate of energy loss per unit path length, -dE/ dz. Finally, the theoretical results for the Drell Yan differential cross-section ratios are compared with the E772 and E866 data. It is found that the theoretical results are in good agreement with the experimental data.     

Baryon bound state in two-dimensional SU(N) gauge theory

The bound-state baryon problem with N quarks in an SU(N) gauge model of strong interactions is investigated in one-space and one-time dimensions. A study of planar diagrams yields color singlet “baryon” states of quarks that have infrared divergence-free mass spectra. The resulting integral equation turns out to be identical to the one obtained in a particular string model.