Non-factorizable contributions in D0→π+π- decay

We have analyzed the D^0→π^+π^- decay with α_s corrections in quantum chromodynamic (QCD) factorization and with the soft-gluon corrections in the light cone QCD sum rules. The soft-gluon effects are firstly calculated in the decay channel. The results show that once the factorization contributions, the α_s corrections, and the soft-gluon effects are all considered, we can satisfactorily explain the experimental data in the decay channel.     

Beam Energy Dependence of the π-/π+ Ratio

Using the isospin- and momentum-dependent hadronic transport model IBUU04, the effects of symmetry energy on the π^-/π^＋ ratio are studied. Our investigations are based on the calculations of the ^132 Sn＋^124Sn semi-central collisions at beam energies of 400/AMeV, 600/A MeV and 800/A MeV. It is found that both the transverse momentum and kinetic energy distributions of the π^-/π^＋ ratio are rather sensitive to the symmetry energy, especially around the Coulomb peaks. The position of the Coulomb peak is shown to be nearly independent of beam energy. The sensitivity of the π^-/π^＋ ratio to the symmetry energy decreases as the beam energy increases from 600/A MeV to 800/A MeV.     

Measurement of the hadronic decay current in τ?→π??+vτ

The properties of hadronic Z⁰ decays with final state photons, measured with OPAL at LEP, have been compared with predictions from two different matrix element calculations ofO( _s ). Two calculations, GNJETS and EEPRAD, have been investigated which use different schemes to restrict the phase space around the poles of the cross section. Assuming the E0-JADE jet definition, both calculations describe the data well in large regions of phase space fory _cut values around 0.06. For very large and very small jet-photon masses some deviations from the predictions have been found, indicating the importance of higher order corrections. Significant differences between the calculations are only apparent in the predicted rate of 1-jet plus photon events. The rate is higher in GNJETS which reproduces the data better than EEPRAD.     

e+e－→π+π－π+π－形状因子拟合

基于BABAR实验组对e⁺e^－→π⁺π^－π⁺π^－的反应截面的测量结果, 用VMD模型给出的理论截面拟合实验数据, 首次从单一反应道得到π⁺π^－π⁺π^－末态形状因子的所有参数值.     

Effect of unitarization on the amplitudes for the decays K10 → π+π? and K+ → π+π+π?

The unitarization of the amplitude for the decay process K ₁⁰ → π⁺π⁻ and allowance for the rescattering of final-state pions in the decay process K ⁺ → π⁺π⁺π⁻ make it possible to evaluate, by using the parameters extracted from data on K → 2π decays, the K ⁺ → π⁺π⁺π⁻ decay width. The result agrees with the experimental width value at a level of a few percent. Allowance for corrections for higher order terms of the momentum expansion of the amplitude for the decay process K ⁺ → π⁺π⁺π⁻ leads to the slope-parameter value of g ₊₊₋^th = 0.2182, which agrees with its experimental counterpart, g ₊₊₋^exp = 0.2154 ± 0.0035.     

a2(1320)→π+π+π－过程的三体振幅分析

对a₂(1320)→π⁺π⁺π^－过程的衰变振幅进行张量分析,展示了如何得到三体衰变振幅.     

J/ψ→π03(π+π－)分支比的测定

用BESⅠ的7.8×10⁶J/ψ数据更为精确地测定了J/ψ→π⁰3(π⁺π^－)和J/ψ→ω²(π⁺π^－)的分支比(Br(J/ψ→π⁰3(π⁺π^－))=(2.52±0.06±0.43)%,Br(J/ψ→π⁰3(π⁺π^－))=(1.31±0.09±0.21)%.同时对4π不变质量谱和ωππ不变质量谱进行研究分析,试图观察是否存在有兴趣的信号.     

Lifetime vibrational interference during the NO 1s-1π* resonant excitation studied by the NO+(A 1Π → X 1Σ+) fluorescence

Dispersed fluorescence from fragments formed after the de-excitation of the 1s^-1π^* resonances of N^*O and NO^* has been measured in the spectral range of 118–142 nm. This range is dominated by lines of atomic nitrogen and oxygen fragments and by the bands in the NO⁺ ion which result from the participator Auger decay of the 1s^-1π^* resonances. Ab-initio calculations of the transition probabilities between vibrational levels during the reaction NO N^*O ⇒ NO were used to explain the observed intensity dependence for the fluorescence bands on the exciting-photon energy across the resonances and on both v^′ and v^′′ vibrational quantum numbers. The multiplet structure of the 1s^-1π^* resonance and lifetime vibrational interference explain the observed exciting-photon energy dependence of the fluorescence intensity. A strong spin-orbit coupling between singlet and triplet states of NO⁺ is proposed to reduce additional cascade population of the state via radiative transitions from the and states and to explain remaining differences between measured and calculated integral fluorescence intensities.     

τ±→π±+nπ0+ντ(n=0,1,2)衰变分支比测量

基于北京谱仪收集的4.03GeV质心系能量下e⁺e^－对撞数据,分析τ^±τ^±→e^±+π^±+nπ⁰+ν's(n=0,1,2)事例,给出分支比值Br(τ^±→π^±ν_τ)=(11.64±0.49^+0.76_－0.73%,Br(τ^±→π^±π⁰ν_τ)=(24.00±1.34^+1.36_－1.30%,Br(τ^±→π^±2π⁰ν_τ)=(9.39±1.68^+1.69_－1.66%.     

ρ0 production the reaction ξξ→3π+3π?ξξ→ρ0ρ0(1700)

We have studied the ⁰ production rate in the reaction 3⁺3^– in the energy range 1.6W 7.5 GeV with the CELLO detector at PETRA. Our analysis points to a substantial yield of ^00+– events in particular atW >4.0 GeV. We give cross sections for the ⁰2⁺2^– and ^00+– final states and calculate upper limits for the reaction ⁰⁰ (1700) ^00+–.Now at CERN     

Reaction e + e ? → π + π ? π + π ? at energies of √ s ≤ 1 GeV

The e ⁺ e ⁻ → π ⁺ π ⁻ π ⁺ π ⁻ cross section is calculated for energies of 0.65 ≤ √s ≤ 1 GeV in the framework of the generalized hidden local symmetry model. The calculations are compared with the data of CMD-2 and BaBaR. It is shown that the inclusion of heavy isovector resonances ρ(1450) and ρ(1700) is necessary for reconciling calculations with the data. It is found that, at √s ≈ 1 GeV, the contributions of the above resonances are much larger, by a factor of 30, than the ρ(770) one, and amount to a considerable fraction ∼0.3–0.6 of the latter at √s ∼ m _ρ. The text was submitted by the authors in English.     

弱电流不守恒情况下π-→π0+e+ν过程的几率

利用色散关系研究了弱电流不守恒情况下的π^-→π⁰+e+ν衰变过程。在对π—π散射相移作了一些假定后,证明了π、π中间态的贡献很小。在N、N中间态项中出现的N、N湮灭矩阵元用Chew-Ball理论及湮灭实验估计,同时出现的核子弱作用形状因子又用色散关系计算,证明了N、N中间态对它的贡献很小,计算了π、π中间态对它的贡献。根据现有N、N湮灭实验估计,π^-→π⁰+e+ν过程的衰变几率<6×10^-4秒^-1。     

Measurement of inclusive π 0 production in hadronic Z 0 decays

An analysis is presented of inclusiveπ ⁰ production inZ ⁰ decays measured with the DELPHI detector. At low energies,π ⁰ decays are reconstructed by using pairs of converted photons and combinations of converted photons and photons reconstructed in the barrel electromagnetic calorimeter (HPC). At high energies (up to ) the excellent granularity of the HPC is exploited to search for two-photon substructures in single showers. The inclusive differential cross section is measured as a function of energy forqq andbb events. The number ofπ ⁰’s per hadronicZ ⁰ event isN(π ⁰)/Z _had ⁰ =9.2±0.2(stat)±1.0(syst) and forbb events the number ofπ ⁰’s is N(π ⁰)/bb=10.1±0.4(stat)±1.1(syst). The ratio of the number ofπ ⁰’s inbb events to hadronicZ ⁰ events is less affected by the systematic errors and is found to be 1.09±0.05±0.01. The measuredπ ⁰ cross sections are compared with the predictions of different parton shower models. For hadronic events, the peak position in theξ _p=ln(1/x_p) distribution isξ* _p =3.90 _−0.14 ^+0.24 . The average number ofπ ⁰’s from the decay of primary B hadrons is found to be N(B→π ⁰ X)/B hadron=2.78±0.15(stat)±0.60(syst).     

Analysis of the decay B0→χclπ0 with light-cone QCD sum rules

In this article,we calculate the contribution from the nonfactorizable soft hadronic matrix element to the decay B~0→χc1~π~0 with the light-cone quantum chromo-dynamic(QCD) sum rules.The numerical results show that its contribution is rather large and should not be neglected.The total amplitudes lead to a branching fraction which is in agreement with the experimental data marginally.     

Measurement of the f1(1285) → π+π−π0 decay

The isospin symmetry-breaking (ISB) decay f ₁(1285) → π⁺π^?π⁰ has been studied at the VES facility. The branching ratio is measured: $\frac{{BR\left( {f_1 \to \pi ^ + \pi ^ - \pi ^0 } \right)}} {{BR\left( {f_1 \to \eta \pi ^ + \pi ^ - } \right)}} = 0.86 \pm 0.16_{ - 0.20}^{ + 0.70} \%Low-energy resonances in ³¹P(p, α ²⁸Si and ³⁵Cl(p, α)³²S were studied directly in order to gain a better understanding of reaction cycling in the Si-Ar region in novae. New resonance strengths at E _c.m. = 600 and 622 keV in ³¹P(p, α)²⁸Si were measured (ωγ _{p, α} = (2.2#x00B1;0.7) × 10^?2 eV and ωγ _{p, α} = (0.99±0.08) eV, respectively) as well as the E _c.m. = 610 keV resonance in ³⁵Cl(p, α)³²S [ωγ _{p, α} = (1.2±0.2) × 10^?2 eV], the lowest energy that any resonance in this reaction has been observed, directly or indirectly. The strengths of these resonances were found to be lower than previously determined, resulting in even weaker cycling in the Si-Ar region.     

Correlation and polarization characteristics of the 40Ca(p, dπ+)39K reaction

The ⁴⁰Ca(p, dπ⁺)³⁹K reaction was studied theoretically at a proton energy of 650 MeV within the distorted wave impulse approximation (DWIA) and under the assumption of a quasi-free mechanism of the elementary process pp → dπ⁺ of pion production. The peripheral nature of the reaction on the nucleus was shown. The influence of the effects of distortions in the initial and final states of the reaction on the differential cross section and other spin-dependent characteristics are discussed.     

在J/ψ衰变与ρ→π+π–π0衰变中的ρ–ω干涉

通过分析J/ψ→π⁺π^-π^{0π0来研究ρω干涉.利用描述J/ψ衰变的一般的唯象模型对PDG-2002关于J/ψ衰变到PP和PV的实验数据做了拟合(P表示赝标介子,V表示矢量介子) ,得到ρ0→π+π-π0反常大的分支比～10-3—10-2.理论的分析结果也与这一反常大的分支比相符合.同时,得到了合理的ηη′混合角和组分夸克质量比:θ=-19.68°±1.49°,m_u/m_s≈0.6 .}     

Review of the Low-Lying Excited Baryons ∑*（1/2-）

<正>Strong empirical and phenomenological indications exist for large sea-quark admixtures in the low-lying excited baryons. Investigating the low-lying excited baryon ∑^*（1/2^-） is important for determining the nature of the low-lying excited baryons. We review the experimental and theoretical progress on the studies of the ∑^*（1/2^-）.     

F2 Σ+ -X 2Σ +Band System of Cobalt Carbide

用脉冲直流放电产生Xe原子亚稳态5p56s[3/2]2和5p56s′[1/2]0.在单光子28000－42000cm-1能量范围内,结合飞行时间质谱技术获得Xe原子共振增强激发光谱.光谱分析表明,所有谱线来源于Xe原子5p56s[3/2]2和5p56s′[1/2]0两个亚稳态吸收单个光子向偶宇称np′、nf′自电离Rydberg态序列的跃迁.实验观测到许多新的自电离能级,并获得更精确和系统的能级位置和量子亏损值数据.