Model independent constraints from vacuum and in-medium QCD Sum Rules

We discuss QCD sum rule constraints based on moments of vector meson spectral distributions in the vacuum and in a nuclear medium. Sum rules for the two lowest moments of these spectral distributions do not suffer from uncertainties related to QCD condensates of dimension higher than four. We exemplify these relations for the case of the ω meson and discuss the issue of in-medium mass shifts from this viewpoint. Received: 22 December 1998 / Revised version: 13 January 1999     

Glauber gluon effects in soft collinear factorization

Effects of Glauber gluons, which cause the elastic scattering process between different jets, are studied in the frame of soft-collinear effective theory. Glauber modes are added into the action before being integrated out, which is helpful in studies on the Glauber couplings of collinear and soft particles. It is proved that the final state interactions cancel out for processes inclusive enough. So are interactions with the light cone coordinates x⁺ and x⁻ greater than those of the hard collision. The eikonalization of Glauber couplings of active particles and absorption of these couplings into soft and collinear Wilson lines are discussed, which is related to the loop level definitions of Glauber gluons here. The active-spectator coherence is proved to be harmless to the inclusive summation of spectator-spectator and spectator-soft Glauber exchanges. Based on this result, spectator-spectator and spectator-soft Glauber exchanges cancel out in the processes considered here. Graphic aspects of the cancellation are also discussed to explain relations between the graphic and operator level cancellation of Glauber gluons.     

Λ(1405) as a multiquark state

In the QCD sum rule approach we predict the Λ (1405) mass by choosing the π⁰Σ⁰ multiquark interpolating field. It is found that the mass is about 1.419 GeV from Π₁ (q ²) sum rule which is more reliable than Π_q (q ²) sum rule, where Π_q (q ²) and Π₁ (q ²) are two invariant functions of the correlator Π (q ²). We also present the sum rules for the K ⁺ p and the π⁺Σ⁺ multiquark states, and compare to those for the π⁰Σ⁰ multiquark state. The mass of the Λ (1600) can be also reproduced in our approach. Received: 11 November 1997 / Revised version: 28 April 1998     

高能极限下部分子饱和及部分子演化规律研究

基于Mueller的偶极子理论框架,研究了高能部分子随快度的演化规律,计算了高能部分子的劈裂几率。本文采用一个新颖的近似方法,简化了部分子演化方程,并计算出了该方程在饱和区域中的解析解,本文的研究为理论上建立电子-质子和质子-核散射模型提供了有力的保障,为实验上解释电子-质子和质子-核散射实验数据提供了理论基础。     

识别Z玻色子喷注的卷积神经网络方法

高能物理中喷注识别任务是从背景中识别出感兴趣的特定信号,这些信号对于在大型强子对撞机上发现新的粒子,或者新的过程都有着非常重要的意义.量能器中产生的能量沉积可以看做是对喷注的一种拍照,分析这样产生的数据在机器学习领域中属于一个典型的视觉识别任务.基于喷注图片,本文探索了利用卷积神经网络(convolutional neural networks,CNNs)识别量子色动力学背景下的Z玻色子喷注,并与传统的增强决策树(boosted decision trees,BDTs)方法进行了对比.在本文利用的输入前提下,三种相关的性能参数表明,CNN比BDT带来了约1.5倍的效果提升.除此之外,通过最优与最差的喷注图与混淆矩阵,说明了CNN通过训练学习到的内容与整体识别能力.     

Semi-inclusive deep inelastic lepton scattering off complex nuclei

It is shown that in semi-inclusive deep inelastic scattering (DIS) of electrons off complex nuclei, the detection, in coincidence with the scattered electron, of a nucleus (A−1) in the ground state, as well as of a nucleon and a nucleus (A−2), also in the ground state, may provide unique information on several long standing problems, such as: i) the nature and the relevance of the final state interaction in DIS; ii) the validity of the spectator mechanism in DIS; iii) the medium induced modifications of the nucleon structure function; iv) the origin of the EMC effect. Received: 4 March 1999     

On the colour contribution to effective weak vertex in broken colour gauge theories

Treating the breaking of colour symmetry via the mixing between the colour gluons and weak bosons (a la Rajasekaran and Roy) it is observed that the colour contribution to the effective weak vertex of a quark at zero momentum transfer is zero uptoO(α). An erratum to this article is available at .     

SU(3) Local Gauge Field Theory as Effective Dynamics of Composite Gluons

The effective dynamics of quarks is described by a nonperturbatively regularized NJL model equation with canonical quantization and probability interpretation. The quantum theory of this model is formulated in functional space and the gluons are considered as relativistic bound states of colored quark-antiquark pairs. Their wave functions are calculated as eigenstates of hardcore equations, and their effective dynamics is derived by weak mapping in functional space. This leads to the phenomenological SU(3) gauge invariant gluon equations in functional formulation, i.e., the local gauge symmetry is a dynamical effect resulting from the dynamics of the quark model.     

一种计算动量空间胶子场三线顶角费曼规则的新方法

利用描述夸克与胶子间色相互作用的有效拉氏量密度Ψeff得到一种计算动量空间胶子场三线、四线顶角费曼规则的新方法.