Masses and Widths of Light Scalar Mesons in Chiral Perturbation Theory

Based on the diquark model, we assume that the light scalar mesons are q^2q^-2 states rather than qq^-. The chiral effective Lagrangian for the light scalar meson is constructed, and the mass relations are obtained： the isotriplet （a0） and the isosinglet （f0） are the heaviest and are degenerate, the isodoublets （κ） are heavier and the other isosinglet （σ） is the lightest; and 2Mκ^2 = Mα0^2＋ Mσ^2. Using experimental value for a0 and σ mass, we obtain Mκ=794 MeV, which is consistent with the experimental value. Then taking Г（a0^0 →ηπ^0） = 90 MeV and Г（f0→π^0π^0） = 20 MeV, we get the width of σ is： Г（σ0→π^＋π^-）= 150 MeV.

KLOE results on scalar and pseudoscalar mesons

The data collected by the KLOE Collaboration at the Frascati φ-factory DAФNE from 2001 to 2006 have been used for extensive studies in meson spectroscopy. The decays of the scalar mesons a0（980） and f0（980） into two pseudoscalar mesons have been exploited to measure the relevant parameters of those resonances. The radiative decays φ →ηγ and η＇γ have been used for the determination of the pseudoscalar mixing angle and to search for a possible gluonium content in the η＇. The dynamics of the η → 3π decay has been studied and the Dalitz Plot parameters have been measured. The large amount of η mesons produced allowed also to study interesting rare η decays.

Dynamical study of light scalar mesons below 1GeV in a flux-tube model

The light scalar mesons below 1GeV configured as tetraquark systems are studied in the framework of the flux-tube model. Comparative studies indicate that a multi-body confinement,instead of the additive two-body confinement, should be used in a multiquark system.The σ and κ mesons could be well accommodated in the diquark-antidiquark tetraquark picture, and could be colour-confinement resonances. The a0（980） and fo（980） mesons are not described as KK molecular states and ns diquark-antidiquark states.However, the mass of the first radial excited state of the diquark-antidiquark state, nn is 1019 MeV,is close to the experimental data of the fo （980）.

Three-body force and the tetraquark interpretation of light scalar mesons

We study the possible tetraquark interpretation of light scalar meson states ao（980）, f0（980）,k, within the framework of the non-relativistic potential model. The wave functions of tetraquark states are obtained in a space spanned by multiple Gaussian functions. We find that the mass spectra of the light scalar mesons can be well accommodated in the tetraquark picture if we introduce a three-body quark interaction in the quark model. Using the obtained multiple Gaussian wave functions, the decay constants of tetraquarks are also calculated within the ＂fall apart＂ mechanism.

Scalar mesons and glueballs in D_p-D_q hard-wall models

We investigate the light scalar mesons and glueballs in the Dp-Dq hard-wall models, including D3-Dq, D4-Dq, and D6-Dq systems. It is found that only in the D4-D6 and D4-Ds hard-wall models are the predicted masses of the clq scalar meson fo scalar glueball consistent with their experimental or lattice results. This indicates that D4-D6 and D4-Ds hard-wall models are the favorite candidates of the realistic holographic QCD model.

Scalar meson spectroscopy with a fine lattice

With sufficiently light u and d quarks the isovector （a0） and isosinglet （f0） scalar meson propagators are dominated at large distances by two-meson states. In the staggered fermion formulation of lattice QCD, taste-symmetry breaking causes a proliferation of multihadron states that complicates the analysis of these channels. Of special interest is the bubble contribution, which makes a considerable contribution to these channels. Using numerical simulation we have measured the correlators for both a0 and f0 channels in the ＂Asqtad＂ improved staggered fermion formulation in a MILC fine （a = 0.09 fm） lattice ensemble. We analyze those correlators using rooted staggered chiral perturbation theory （rSxPT） and achieve chiral couplings that are well consistent with previous determinations.

Multiquark states and the mixing of scalar meson

In order to describe Kaon-Nucleon scattering data, the mixing of scalar meson σ0 and σs must be introduced in the chiral SU（3） quark model. Inspired by this, now the mixing of scalar meson is further considered to study some interesting dibaryons in the chiral SU（3） quark model. The results show that the mixing of scalar meson has different effects on these dibaryons.

A note on scalar meson dominance

We consider chiral perturbation theory with an explicit broad σ-meson and study its contribution to the scalar form factors of the pion and the nucleon. Our goal is to learn more about resonance saturation in the scalar sector.

On Radiative Decay of Heavy Vector Mesons <i>V</i>&rarr;<i>P&gamma;</i>in the Scalar Strong Interaction Hadron Theory

Radiative decay of heavy ground state vector meson V → P&gamma;is treated semi-classically in the scalar strong interaction hadron theory. The treatment successfully employs the new wave function of the vector meson updated here. The ratio of the available J/ψ and decay rates agrees with prediction. The values of the predicted rates are also in order of magnitude agreement with measurements. These agreements are the only ones directly computed from a first principles’ theory.

On Excited Meson Spectra in the Scalar Strong Interaction Hadron Theory

Meson spectra have been treated earlier in the scalar strong interaction hadron theory, choosing the Coulomb and linear type of potentials, neglecting the quadratic one. The spectra of ground state pseudoscalar and vector mesons were adequately accounted for but not that of the excited mesons. Here, the quadratic potential replaces the Coulomb one and the same ground state meson spectra were recovered. Also, the masses of low-lying radially excited pseudoscalar and vector mesons were found to be 4% - 18% smaller than the measured ones. Here, the linear type of potential, by itself of nonlinear nature, has been neglected. For some orbitally excited pseudoscalar mesons, the difference is 14% - 38%. The discrepancies are tentatively attributed to the neglected nonlinear potential, which is expected to increase with meson mass, as can be seen in the tables below.

Chiral Lagrangian Treatment of 0^＋＋ Mesons and 0^＋＋ Glueballs

Within the framework of a nonlinear chiral Lagrangian the mass spectra and the decay properties of 0^＋＋ states below 2 GeV are studied. Assuming that f0（980）, a0（980）, K0（1430）, and f0（1500） comprise an SU（3） nonet, we make a detailed prediction about the static properties of the 0^＋＋ mesons. The substructure analysis of these states in terms of two- and four-quark components as well as a glueball component is carried out. We also consider the interaction Lagrangian and provide a preliminary study of the strong and radiative decays of the 0＋＋ mesons. The scalar glueball masses and partial widths are also presented. In view of the fact that few data of 0＋＋ mesons are clearly given in the present PDG （Particle Data Group） list and that the four-quark content of mesons is a hot issue both experimentally and theoretically, the predicted results of the paper may be helpful for upcoming experimental and theoretical studies of these mesons.

进一步探讨H粒子的结构

利用手征SU(3)夸克模型和推广的手征SU(3)夸克模型,在集团组态下研究了H粒子的结构,分析了两种不同的短程相互作用机制即矢量介子交换效应和单胶子交换效应、不同的禁闭势、耦合道及标量介子混合角等因素对H粒子结合能的影响.研究表明,准确的实验信息将有助于检验理论模型,决定如何选取禁闭势和是否需要考虑标量介子混合角等问题.

奇异数为-6的双重子结构

在手征SU(3)夸克模型和推广的手征SU(3)夸克模型下,利用共振群方法研究了奇异数为-6的双重子ΩΩ的结构.分析了波函数宽度,夸克交换效应以及标量介子混合角对系统结合能的影响.结果表明,宽度越小越容易形成束缚态,夸克交换效应有利于形成束缚态.标量介子混合角对系统结合能的影响很大,不同的混合角下系统的结合能不同.

奇异数为-5的双重子态结构

在手征SU(3)夸克模型和推广SU(3)手征夸克模型下,应用共振群方法研究了奇异数为-5的双重子系统的结构,主要分析了标量介子混合角对系统结合能的影响.结果表明,无论是哪种混合,双重子Ξ*Ω都是束缚态.在手征夸克模型下,混合角为-18°和19°时,Ξ*Ω系统结合能大致相同;但在理想混合下,因为σ场没有贡献,系统的结合能会大大减少.同时还发现,考虑混合角时的结合能远小于不考虑混合角时的结合能.本文工作对标量介子混合角问题的研究提供了一些有意义的信息.

Unparticle引起的轻子味破坏衰变

在Unparticle物理模型下讨论了轻子味破坏(LFV)衰变τ-→l-(V0,P0)(其中l=e,μ,V0(P0)代表中性矢量介子和赝标介子).首先提出了Unparticle物理与标准模型粒子有效相互作用模型,然后详细计算了τ-→l-(V0,P0)的衰变宽度和分支比,系统分析了所有相关实验对耦合常数限制,并给出了适当的参数空间.结果表明:在确定参数空间内,τ→lP0衰变模式具有很小的分支比,在实验上无法观测到;而在许多参数与空间内,τ→lV0衰变模式的分支比具有量级O(10-10～10-8),这在将来的LHC和超B工厂是可以观测的.

标量介子混合角对五夸克态结合能的影响

在手征SU(3)夸克模型下,考虑了标量介子混合角,研究奇异数为+1的五夸克态的性质.首先,在平方型色禁闭势下,计算了自旋和宇称Jπ分别为1/2-和1/2+态的结合能,结果表明同位旋T=0态的能量总是最低,其组态[4]orb[31]σfts=01s-的最低能量为1 893MeV.然后,在误差函数型色禁闭势下,做了相同的计算,发现误差函数型相互作用对Jπ=1/2-系统提供吸引力,对Jπ=1/2+态提供排斥力.但不论采取哪种禁闭势,所计算的五夸克系统结合能仍然比LEPS实验组报道的质量1 540 MeV高出300 MeV左右.

TC理论中矢量介子衰变研究

由TC理论的有效拉氏量,给出了矢量介子与标量介子相互作用顶角,讨论了中性矢量介子相互作用顶角,讨论了中性矢量介子各种可能的衰变,并且具体计算了衰变因子A。

Analysis of X（1576） as a Tetraquark State with the QCD Sum Rules

We take the viewpoint that X（1576） is the tetraquark state which consists of a scalar diquark and an antiscalar-diquark in relative P-wave, and calculate its mass in the framework of the QCD sum rule approach. The numerical value of the mass mx= （1.66 =k 0.14） GeV is consistent with the experimental data. There might be some tetraquark components in the vector meson X（1576）.

B→a_0(1450)ρ(ω) Decays in Perturbative QCD Approach

In the two-quark model supposition for the meson ao（1450）, which can be viewed as either the first excited state （scenario I） or the lowest lying state （scenario II）, the branching ratios and the direct CP-violating asymmetries for decays B→a0（1450）ρ（ω） are studied by employing the perturbative QCD factorization approach. We find the following results： （a） For the decays B- B→a0（1450）ρ- andB→a0^＋（1450）ρ^-, their branching ratios have large difference between two scenarios. Although their branching ratios are larger than other considered decay modes, their direct CP-violating asymmetries in both scenarios are small. （b） For the decays B-→a0^-（1450）ρ0 and B0→ a0（1450）ρ＋, a0^0（1450）ρ0, a00 （1450）w, their branching ratios are dose to each other between two scenarios, respectively. （c） Comparing with the decays a0^0（1450）ρ0,π0ρ0 π0π0, the decay B-→a0^-（1450）ρ0 receives a larger branching ratio in each scenario, which is sensitive to the variation of the Cabibbo-Kobayashi-Maskawa angle α.

Comparison of Properties of the Simplest Neutron Stars in Three RMF Models

We study some properties of the simplest neutron stars （NSs） in the Glendenning Moszkowski （GM） model, the hybrid derivative coupling （HD） model and the Zimanyi Moszkowski （ZM） model in the framework of relativistic mean field （RMF） theory with and without the interaction by exchanging the ^-meson. We show that the maximal mass of the NSs becomes smaller, but the redshift becomes larger from the GM model to the HD model, then to the ZM model. The interaction with the 6-meson exchange enlarges the maximal mass of neutron stars, increases the relative population of charged particles （proton, electron and muon） and descends the relative population of neutron.