A note on the mass splitting of K*(892)

Belle Collaboration reported a new observed value of K*-(892) mass by studying τ- → KSπ-ντ decay, which is significantly different from the current world average value given by Particle Data Group 2006. Motivated by this new data, we revisit the issue on the K*0(892)-K*±(892) mass splitting. Our theoretical estimation favors the new measurement by Belle Collaboration. Therefore further experimental efforts are urgently needed to improve our understanding of these issues.     

f0(400—1200)物理本质的探讨

对f₀(400—1200)的物理本质进行了探讨,将其分解为三部分:t道ρ介子和f₂(1270)介子交换部分以及一个很宽的s道共振态f₀(X).在ππ不变质量1.2GeV以下,用t道ρ介子交换就可以很好地解释同位旋为2的ππS波散射实验数据.但是,在能量高于1.2GeV时,t道f₂(1270)介子交换的贡献必须计入.利用同位旋为2的ππS波散射过程对t道ρ介子和f₂(1270)介子交换中的形状因子进行约束,通过重新拟合CERN-Munich(CM)实验数据来获得f₀(X)的参数.结果表明,确实需要引入一个在1.6—1.7GeV附近具有极点的较宽的0⁺⁺的共振态,其极点是(1.69–0.26i)GeV.     

在BEPCⅡ/BESⅢ上测量K((892)质量劈裂的Monte Carlo研究

对BEPCⅡ BESⅢ上的J ψ→K±K (892 ) 和J ψ→K0 K (892 ) 0 过程进行了MonteCarlo模拟,对测量K (892 )的质量劈裂的可行性进行了研究.在BESⅢ探测器的设计指标下,采用6×10 8J ψ数据,若输入K (892)0 和K(892)±的质量差为6 0 0MeV ,经过BESⅢ模拟和拟合后的质量差则是5 79±0 16±0 13MeV ,其中第一项误差为统计误差,第二项误差为系统误差.这表明,BESⅢ的建造将为精确测量K (892 )质量劈裂提供极佳机遇.     

J/ψ→γγV(ρ,φ)衰变的实验研究

利用北京谱仪(BES)收集的7.8×10⁶ J/ψ事例,对J/ψ→γγV(ρ,φ)衰变道中的η(1430)共振态进行了分析.从J/ψ→γγρ衰变模式得到其质量及衰变宽度分别为1431±17MeV和88±28MeV,衰变分支比Br(J/ψ→γη(1430))Br(η(1430)→γρ)=(1.1±0.5±0.3)×10^－4;而从J/ψ→γγφ衰变模式得到其质量及衰变宽度分别为1424±15MeV和73±58MeV,衰变分支比Br(J/ψ→γη(1430))Br(η(1430)→γφ)=(2.0±1.0±0.6)×10^－4.     

e+e-实验中ψ(2S)能区连续态单光子湮没过程的贡献

研究了e+e-实验中ψ(2S)能区连续态单光子湮没过程的截面对观测总截面的贡献. 针对ψ(2S)质量处ωπ0和π+π-两个观测末态,利用唯象模型估计了单光子湮没过程贡献的大小. 分析表明,对于ψ(2S)→ωπ0和ψ(2S)→π+π-,以及其他电磁末态分支比的确定,单光子湮没过程的贡献必须认真考虑. 通过研究,我们认为对于BES实验来说,为了获得共振态电磁末态分支比的正确结果,至少需要在低于ψ(2S)共振峰的能量点采集10pb-1的数据.     

D介子衰变中的奇异轴矢介子(英文)

目前,奇异轴矢介子的性质并没有被很好地理解,而这类介子是可以在D介子衰变中得到更多的研究。将窄宽近似下的等式关系和强衰变中CP守恒应用到四体衰变D0 → K+K-π+π-中的D0 → K±K₁?（1270）（→ρK or K*π）的实验数据中,可以发现实验数据与理论存在矛盾,然而,当考虑更多K₁（1270）的衰变过程后,可以发现,B（D0 → K-K₁+（1270）（→ K*0π+））的实验数据很可能被高估了一个量级。考虑共振态K₁（1400）的贡献,利用因子化方法计算相应的衰变过程的分支比,可以发现,B（D0 → K-K₁+（1400）（→ K*0π+））的分支比与使用等式关系得到的B（D0 → K-K₁+（1270）（→ K*0π+））的分支比在量级上是相同的。另外,对于含有奇异轴矢介子的D介子衰变实验数据的合理性,实验可以通过测量K₁（1270）→ ρK和K*π分支比的比值来检验,或者通过验证D介子衰变中的等式关系来检验。     

e+e－实验中ψ(2S)能区连续态单光子湮没过程的贡献

研究了e⁺e^－实验中ψ(2S)能区连续态单光子湮没过程的截面对观测总截面的贡献.针对ψ(2S)质量处ωπ⁰和π⁺π^－两个观测末态,利用唯象模型估计了单光子湮没过程贡献的大小.分析表明,对于ψ(2S)→ωπ⁰和ψ(2S)→π⁺π^－,以及其他电磁末态分支比的确定,单光子湮没过程的贡献必须认真考虑.通过研究,我们认为对于BES实验来说,为了获得共振态电磁末态分支比的正确结果,至少需要在低于ψ(2S)共振峰的能量点采集10pb^－1的数据.     

强子物质中的介子-介子散射(英文)

建立了一个夸克交换模型和提出了一个夸克-反夸克湮灭模型来研究介子-介子散射。从量子色动力学我们得到一个依赖于温度的夸克作用势。从微扰量子色动力学推导对应于夸克-反夸克湮灭和产生的跃迁势。模型给出基态介子质量的实验值,并且在玻恩近似下能说明真空中阈能附近的π-π弹性散射相移的实验值。从S矩阵元出发,推导散射的跃迁振幅和截面公式。计算出涉及π,ρ,K,K*的反应的非极化截面。发现这些截面具有强烈的温度依赖性。We have established a quark-interchange model and have proposed a quark-antiquark annihilation model to study meson-meson scattering. From QCD we obtain a temperature-dependent quark potential. The transition potential corresponding to quark-antiquark annihilation and creation is derived in perturbative QCD. The experimental ground-state meson masses are reproduced and the experimental data of elastic phase shifts for ππ scattering near the threshold energy in vacuum can be accounted for in the Born approximation. Starting from S-matrix element, we derive the transition amplitude and the cross section for the scattering. Unpolarised cross sections for reactions involving π, ρ, K and K* are calculated. Remarkable temperature dependence of the cross sections is found.     

N巴黎势和可能的p共振态(英文)

通过求解N巴黎光学势的复薛定谔方程,研究了N系统的近阈束缚和共振行为,得到了一个p系统的13P0共振态.发现其能量和宽度与最近BES用Breit Wigner(B W)公式分析J/ψ→γp衰变的实验数据给出的结果相容.讨论了这一结果的含义及进一步研究的建议.     

Centrality Dependence of K~*(892)~0 and φ(1020) Production at LHC

We study the centrality dependence of the mid-rapidity(|y| 0.5) yields and transverse momentum distributions of K~*(892)~0 and φ(1020) resonances produced in Pb + Pb collisions at sNN~(1/2)= 2.76 TeV. The midrapidity density( dN/dy) and the shape of the transverse momentum spectra are well reproduced by an earlier proposed Unified Statistical Thermal Freeze-out Model(USTFM), which incorporates the effects of both longitudinal as well as transverse hydrodynamic flow. The freeze-out properties in terms of kinetic freeze-out temperature and transverse flow velocity parameter are extracted from the model fits to the transverse momentum data provided by the ALICE experiment at the LHC. The kinetic freeze-out temperature is found to increase with decreasing event centrality while the transverse flow velocity parameter shows a mild decrease on moving towards peripheral collisions. Moreover the centrality dependence of the mid-rapidity system size at freeze-out has also been studied in terms of transverse radius parameter.     

Electromagnetic Masses Anomaly of K*(892) in the Massive Yang-Mills Theory

Electromagnetic mass difference between neutral K^* and charged K^* has been calculated in the U(3)_L×U(3)_R chiral field theory of mesons. It has been revealed that the on-Abelian gauge structure of the massive Yang-Mills Lagrangian obeyed by K^* plus VMD (vector meson dominance) causes the EM-mass of neutral one larger than charged one. Experiment supports this anomaly effect.     

A note on the mass splitting of K*(892)

Belle Collaboration reported a new observed value of K*-(892) mass by studying τ- → Ksπ-γτ decay, which is significantly different from the current world average value given by Particle Data Group 2006.Motivated by this new data, we revisit the issue on the K*0(892)-K*±(892) mass splitting. Our theoreticalestimation favors the new measurement by Belle Collaboration. Therefore further experimental efforts are urgently needed to improve our understanding of these issues.     

Study of K*(892) mass and width splitting caused by model difference

According to the new K*(892)0 and K*(892)- masses reported by the BELLE experiment and the K*(892)0 mass reported by the FOCUS experiment, mass splitting between neutral and charged K*(892) becomes very small. This is significantly different from the current world average values given by the Particle Data Group 2008. We find that there are differences between models used to fit the K*(892) decay invariant mass spectra in different measurements and study the model dependence in the measurement of K*(892) parameters. We refit the K*(892)0 mass spectra of the BELLE and FOCUS experiments with the formula used by BELLE in fitting K*(892)- to get new mass and width. After refitting, the K*(892)0 mass of the BELLE experiment becomes 1.4 MeV/c2 larger than the initial value and that of the FOCUS experiment is 1 MeV/c2 smaller than the initial value. We also fit the spectra of some other experiments to extract the K*(892) parameters using the BELLE K* (892)- parametrization.     

\bar K^{0*} (892) andK 0*(892) production at lowp t and the quark parton model

Data on the production of the neutralK ^*(892) resonances at lowp _t by 200 GeVK ^? and π^? is compared with the predictions of various models based on the quark parton model of hadrons.     

Mass and KLamda coupling of the N*(1535)

Using a resonance isobar model and an effective Lagrangian approach, from recent BES results on J/psi-->ppeta and psi-->pK+Lamda, we deduce the ratio between effective coupling constants of N*(1535) to KLamda and peta to be R=gN*(153)KLamda/gN*(1535)peta=1.3+/-0.3. With the previous known value of gN*(1535)peta, the obtained new value of gN*(1535)KLamda is shown to reproduce recent pp-->pK+Lamdanear-threshold cross section data as well. Taking into account this large N*KLamda coupling in the coupled channel Breit-Wigner formula for the N*(1535), its Breit-Wigner mass is found to be around 1400 MeV, much smaller than the previous value of about 1535 MeV obtained without including its coupling to KLamda. The implication on the nature of N*(1535) is discussed.     

Amplitude analysis of the B+/--->phiK*(892)+/- decay

We perform an amplitude analysis of B+/--->phi(1020)K*(892)+/- decay with a sample of about 384 x 10(6) BB[over ] pairs recorded with the BABAR detector. Overall, twelve parameters are measured, including the fractions of longitudinal fL and parity-odd transverse f perpendicular amplitudes, branching fraction, strong phases, and six parameters sensitive to CP violation. We use the dependence on the Kpi invariant mass of the interference between the JP=1(-) and 0+ Kpi components to resolve the discrete ambiguity in the determination of the strong and weak phases. Our measurements of fL=0.49+/-0.05+/-0.03, f perpendicular=0.21+/-0.05+/-0.02, and the strong phases point to the presence of a substantial helicity-plus amplitude from a presently unknown source.     

金核——金核与质子-质子对撞中矢量介子K0(892)和φ(1020)的自旋排列

We present the preliminary results on the spin alignment matrix element ρ₀₀ for vector mesons K^*0(892) and φ(1020) in mid-central (20%—60%) Au+Au and p+p collisions at s_NN=200GeV. The values of ρ₀₀ with respect to reaction plane in Au+Au collisions are 0.36±0.02(stat)±0.13(sys) for K^*0(892) and 0.38±0.01 (stat)±0.04 (sys) for φ(1020). No evident global spin alignment with respect to reaction plane is observed in the measured p_T region up to 5GeV/c with current sensitivity. ρ₀₀ with respect to the production plane of the vector meson is also measured for K^*0(892) and φ(1020) in Au+Au collisions, and for φ(1020) in p+p collisions. No significant difference for the ρ₀₀ between Au+Au and p+p collisions is observed with our data sample.