New Terms for Compact Form of Electroweak Chiral Lagrangian

<Abstract>The compact form of the electroweak chiral Lagrangian is a reformulation of its original form and is expressed in terms of chiral rotated electroweak gauge fields,which is crucial for relating the information of underlying theories to the coefficients of the low-energy effective Lagrangian.However the compact form obtained in previous works is not complete.In this letter we add several new chiral invariant terms to it and discuss the contributions of these terms to the original eleetroweak chiral Lagrangian.

Calculation of Quark Condensate in Nuclear Matter with the Chiral Symmetry Spontaneous Breaking Lagrangian

Using the chiral symmetry spontaneous breaking Lagrangian with mean-field approximation, we investigate Meanwhile, the desent deviates from the linear decrease and becomes remarkably slow as the density of the nuclear matter further increases. It shows that the chiral symmetry spontaneous breaking is only partially restored in densed nuclear matter.

利用手征微扰理论计算强子八重态的质量

作者用手征微扰理论建立了有效拉氏量,对夸克标量流作用于强子八重态上的质量矩阵元计算到一圈图,得到了八重态强子的质量劈裂.

J^p=(1/2)^-五夸克态的手征拉氏量及强衰变

在Jaffe和Wilczek双夸克模型框架下,建立Jp=(1/2)^-五夸克八重态和单态的手征拉氏量,由拉氏量的具体表达式得到这些负宇称五夸克态的强衰变模式及选择定则。通过对这些强衰变模式的分析,可以得出一个结论:p8和n8是两个窄共振态。

物理的唯象学和格点手征延拓研究（英文）

首先在有效场论框架下对η和η'唯象学进行了全面的研究,主要包括两种类型的衰变过程:一种是只含有轻味强子的过程;另一种是有J/ψ参与的反应过程.通过拟合大量相关的衰变宽度和形状因子的实验数据,我们确定了有效拉氏量中自由参数的取值,同时也给出了双混合角机制下的η-η'混合参数.结合通过实验数据定出的混合参数以及格点量子色动力学数值模拟给出的轻赝标介子质量和衰变常数,我们在U(3)手征微扰理论框架下对η-η'混合进行了次次领头阶的分析,并给出了更新的低能耦合常数的数值.

Dirac and Pauli form factors of nucleons using nonlocal chiral effective Lagrangian

Dirac and Pauli form factors are investigated in the relativistic chiral effective Lagrangian.The octet and decuplet intermediate states are included in the one-loop calculation.The 4-dimensional regulator is introduced to deal with the divergence.Different from the non-relativistic case,this 4-dimensional regulator is generated from the nonlocal Lagrangian with the gauge link,which guarantees local gauge invariance.As a result,additional diagrams appear which ensure electric charge 1 and 0 for proton and neutron respectively.The obtained Dirac and Pauli form factors of the nucleons are all reasonable up to relatively large Q;.

Calculations of ■(p^6) Resonance Coupling Constants in Scalar Sector of ENJL Model

我们导出由使用热核扩大从扩大 Nambu Jona-Lasinio 模型联合回声 chiral 理论的常数的分级的回声。

Chiral effective Lagrangian for excited heavy-light mesons from QCD

We derive the chiral effective Lagrangian for excited heavy-light mesons from QCD under proper approximations.We focus on the chiral partners with j_(l)^(P)=3+/2 and j_(l)^(P)=3-/2 which amounts to(1^(+),2^(+))and(1^(-),2^(-))states respectively.The low energy constants including the masses of the chiral partners are calculated.The calculated spectrum for the excited mesons are found roughly consistent with experimental data.In addition,our results indicate that quantum numbers of B_(J)(5970)can be identified with 1^(-)or 2^(-).

Quark Condensate in the Strange Matter

In a nonlinear chiral SU(3) framework, we investigate the quark condensate in the strange matter including N, Σ, Ξ, and Λ, making use of chiral symmetry spontaneous breaking Lagrangian and mean-field approximation. The results show that the chiral symmetry is restored partially when the strange matter density increases and that 〈π→2〉 plays a very important role in the strange matter which may approach the constituents of the neutron stars. In addition, we can find that the strange matter density where the π-condensate emerges leads to the ratio of the nucleon number to baryon number.

Recent development in SU（3） covariant baryon chiral perturbation theory

Baryon chiral perturbation theory （BChPT）, as an effective field theory of low-energy quantum chromodynamics （QCD）, has played and is still playing an important role in our understanding of non-perturbative strong-interaction phenomena. In the past two decades, inspired by the rapid progress in lattice QCD simulations and the new experimental campaign to study the strangeness sector of low-energy QCD, many efforts have been made to develop a fully covariant BChPT and to test its validity in all scenarios. These new endeavours have not only deepened our understanding of some long-standing problems, such as the power-counting-breaking problem and the convergence problem, but also resulted in theoretical tools that can be confidently applied to make robust predic- tions. Particularly, the manifestly covariant BChPT supplemented with the extended-on-mass-shell （EOMS） renormalization scheme has been shown to satisfy all analyticity and symmetry constraints and converge relatively faster compared to its non-relativistic and infrared counterparts. In this article, we provide a brief review of the fully covariant BChPT and its latest applications in the u, d, and s three-flavor sector.

The Λ(1405) state in a chiral unitary approach with off-shell corrections to dimensional regularized loop functions

The Bethe-Salpeter equation is solved in the framework of the unitary coupled-channel approximation by using the pseudoscalar meson-baryon octet interaction. The loop function of the intermediate meson and baryon is deduced in a dimensional regularization scheme, where the relativistic kinetic effect and off-shell corrections are taken into account. Based on the experimental data at the K^-p threshold, the subtraction constants in the loop function are determined. The squared amplitude is suppressed strongly and only one Λ（1405） state is generated dynamically in the strangeness S =-1 and isospin I =0 sector.

Mean-field approximation for the chiral soliton in a chiral phase transition

Using the mean-field approximation, we study the chiral soliton within the linear sigma model in a thermal vacuum. The chiral soliton equations with different boundary conditions are solved at finite temperatures and densities. The solitons are discussed before and after chiral restoration. We find that the system has soliton solutions even after chiral restoration, and that they are very different from those before chiral restoration, which indicates that the quarks are still bound after chiral restoration.

A Study of ρ-ω Mixing in Resonance Chiral Theory

The strong and electromagnetic corrections to ρ-ω mixing are calculated using an SU(2) version of resonance chiral theory up to next-to-leading orders in 1/N_C expansion, respectively. Up to our accuracy, the effect of the momentum dependence of ρ-ω mixing is incorporated due to the inclusion of loop contributions. We analyze the impact of ρ-ω mixing on the pion vector form factor by performing numerical fit to the data extracted from e^+e^-→π^+π^- and τ→ν_τ 2π, while the decay width of ω→π^+π^- is taken into account as a constraint. It is found that the momentum dependence is significant in a good description of the experimental data. In addition, based on the fitted values of the involved parameters, we analyze the decay width of ω→π^+π^-, which turns out to be highly dominated by the ρ-ω mixing effect.

Charmed baryons circa 2015

This is essentially an update of Ref. [1] [H. Y. Cheng, Int. J. Mod. Phys. A 24 （Suppl. 1）, 593 （2009）], a review of charmed baryon physics around 2007. Topics covered in this review include the spectroscopy, strong decays, lifetimes, nonleptonic and semileptonic weak decays, and electromagnetic decays of charmed baryons.

热强子质量的有效手征拉氏量近似

从再现ＱＣＤ标度反常的线性化手征拉氏量出发，使用热场动力学理论，计算了单圈近似下强子的热质量，并发现组分夸克质量和标量场质量在单圈近似下比在平均场近似下随温度的增加更快地下降，而在手征极限下，π介子在所有温度保持无质量。

Study of X(5568) in a unitary coupled-channel approximation of BK and B_sπ

The potential of the B meson and the pseudoscalar meson is constructed up to the next-to-leading order Lagrangian, and then the BK and Bsπ interaction is studied in the unitary coupled-channel approximation. A resonant state with a mass about 5568 MeV and J^P= 0^＋is generated dynamically, which can be associated with the X（5568） state announced by the D0 Collaboration recently. The mass and the decay width of this resonant state depend on the regularization scale in the dimensional regularization scheme, or the maximum momentum in the momentum cutoff regularization scheme. The scattering amplitude of the vector B meson and the pseudoscalar meson is calculated, and an axial-vector state with a mass near 5620 MeV and J^P= 1^＋is produced. Their partners in the charm sector are also discussed.

Isospin violation,light quark masses,and all that

Isospin violation is driven through the light quark mass difference and electromagnetic effects.I review recent progress in extracting the light quark mass difference and tests of the chiral dynamics of Quantum Chromodynamics in various reactions involving light as well as heavy quarks.

The D~* interaction with isospin zero in an extended hidden gauge symmetry approach

The D~* interaction via a ρ or ω exchange is constructed within an extended hidden gauge symmetry approach, where the strange quark is replaced by the charm quark in the SU(3) flavor space. With this D~*interaction, a bound state slightly lower than the D~* threshold is generated dynamically in the isospin zero sector by solving the Bethe-Salpeter equation in the coupled-channel approximation, which might correspond to the X(3872)particle announced by many collaborations. This formulism is also used to study the BB~* interaction, and a BB~* bound state with isospin zero is generated dynamically, which has no counterpart listed in the review of the Particle Data Group. Furthermore, the one-pion exchange between the D meson and the ~* is analyzed precisely, and we do not think the one-pion exchange potential need be considered when the Bethe-Salpeter equation is solved.

New gauge forces beyond the standard model

In this work we investigate the minimal and next to minimal new gauge forces beyond standard model by constructing the corresponding electroweak chiral Lagrangians. Some phenomenological constraints from the mass differences in the K^0-^-K^0,Bd^0-^-Bd^0,Bs^0-^-Bs^0 systems and the corresponding CP violation parameter are discussed.

有效拉氏量理论

按照现代场论观点，所有现在所用的描述现实相互作用的理论都是某种更基本的理论的有效理论，有效理论的一个主要特点是其相互作用项一般是无穷多项．它与通常的可重整场论有很大差别．这里主要讨论一类特殊的有效理论——强作用手征有效拉氏量的理论特点及研究现状．没有涉及强作用中重夸克有效场论理论，ＮＲＱＣＤ理论及它们与手征有效拉氏量结合而形成的理论．