Branching Ratios of J/ψ→π03(π+π－)

The decay mode of J/ψ→π⁰3(π⁺π^－) was studied very little before. There are no informations except branching ratios for this channel in PDG book which based on less than 0.2×10⁶J/ψ events of MARKⅠ. Now, BESⅠ has a data sample of 7.8×10⁶J/ψ events, we can make more accurate results than MARKⅠ. Total of 3290±43 J/ψ→π⁰3(π⁺π^－) events including 1275±86 J/ψ→ω²(π⁺π^－) events are selected. J/ψ→π⁰3(π⁺π^－) and J/ψ→ω²(π⁺π^－) events have been generated with MC simulition for calculating events selection efficiency. BESⅠ result is: Br(J/ψ→π⁰3(π⁺π^－))=(2.52±0.06±0.43)% and Br(J/ψ→π⁰3(π⁺π^－))=(1.31±0.09±0.21)%. Meanwhile, we studied the invariant mass of 4π and ωππ to find interesting signals. It seems that there is a peak at about 1.74GeV in the invarianat mass spectrum of 4π, and a enhancement was also found at about 1.9GeV in the invariant mass spectrum of ωππ. It is not clear whether they are from resonances or background. Therefore, more work in detail is still going on.     

Observation of a pp mass threshold enhancement in ψ′→π+π－J/ψ(J/ψ→γpp) decay

The decay channel ψ′→π⁺π^－J/ψ(J/ψ→γpp) is studied using a sample of 1.06×10⁸ ψ′ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the pp invariant mass spectrum. The enhancement can be fitted with an S-wave Breit-Wigner resonance function with a resulting peak mass of M=1861⁺⁶_－13 (stat)⁺⁷_－26 (syst) MeV/c² and a narrow width that is Γ<38 MeV/c² at the 90% confidence level. These results are consistent with published BESII results. These mass and width values do not match with well established mesons.

     

First evidence of ψ(2S)→Ω-Ω+

The decay ψ(2S)→Ω^-Ω⁺ is analyzed using 14×10⁶ ψ(2S) events recorded by the Beijing Spectrometer Ⅱ (BESⅡ) at the Beijing Electron Positron Collider (BEPC). Based upon events with no missing charged tracks and a satisfactory four-constraint kinematic t, we determine the upper limit for the branching fraction of ψ(2S)→Ω^-Ω⁺ to be 1.5×10⁴ at a 90% confidence level. By including events with one missing charged track, we are able to report the first evidence of an Ω⁺ signal with a statistical signi cance of 3.1|σ. The branching fraction of ψ(2S)Ω⁺ is determined to be (4.80±1.56(stat)±1.30(sys))10⁵.     

Three Body Amplitude Analysis of the Process a2(1320)→π+π+π－

We analyze the decay amplitudes of the process a₂(1320)→π⁺π⁺π^－ using the tensor analysis method and show how to obtain three body amplitudes.     

Measurement of J/ψ decays into ΛΛ π+π-

Based on 58 million J/ψ events collected by the BESⅡ detector at the BEPC, J/ψ→ΛΛ π⁺π^- is observed for the first time. The branching fraction is measured to be Br(J/ψ→ΛΛ π⁺π^-)=(4.30±0.13±0.99)×10^-3, excluding the decays to intermediate states, namely J/ψ→Ξ^-Ξ⁺, J/ψ→Σ(1385)^-Σ(1385)⁺, and J/ψ→Σ(1385)⁺Σ(1385)^-. The branching fractions for these intermediate resonance channels are measured to be:Br(J/ψ→Ξ^-Ξ⁺)=（0.90±0.03±0.18）×10^-3, Br(J/ψ→Σ(1385)^-Σ(1385)⁺)=(1.23±0.07±0.30)×10^-3,and Br(J/ψ→Σ(1385)⁺Σ(1385)^-)=(1.50±0.08±0.38)×10^-3, respectively. The angular distribution is of the form dN/d(cosθ)α(1+αcos²θ) with α=(0.35±0.29±0.06) for J/ψ→Ξ^-Ξ⁺, α=(-0.54±0.22±0.10) for J/ψ→Σ(1385)^-Σ(1385)⁺, and α=(-0.35±0.29±0.06) for J/ψ→Σ(1385)⁺Σ(1385)^-.     

Measurement of J/ψ decays into ΛΛ π+π-

Based on 58 million J/ψ events collected by the BESⅡ detector at the BEPC, J/ψ→ΛΛ π⁺π^- is observed for the first time. The branching fraction is measured to be Br(J/ψ→ΛΛ π⁺π^-)=(4.30±0.13±0.99)×10^-3, excluding the decays to intermediate states, namely J/ψ→Ξ^-Ξ⁺, J/ψ→Σ(1385)^-Σ(1385)⁺, and J/ψ→Σ(1385)⁺Σ(1385)^-. The branching fractions for these intermediate resonance channels are measured to be:Br(J/ψ→Ξ^-Ξ⁺)=（0.90±0.03±0.18）×10^-3, Br(J/ψ→Σ(1385)^-Σ(1385)⁺)=(1.23±0.07±0.30)×10^-3,and Br(J/ψ→Σ(1385)⁺Σ(1385)^-)=(1.50±0.08±0.38)×10^-3, respectively. The angular distribution is of the form dN/d(cosθ)α(1+αcos²θ) with α=(0.35±0.29±0.06) for J/ψ→Ξ^-Ξ⁺, α=(-0.54±0.22±0.10) for J/ψ→Σ(1385)^-Σ(1385)⁺, and α=(-0.35±0.29±0.06) for J/ψ→Σ(1385)⁺Σ(1385)^-.     

Study of ππ final state interactions in ψ(2S)→π+π-J/ψ

The π+π- transition of heavy quarkonia in decay ψ(2S) ψ(2S)→π+π-J/ψ is studied. With the BESII data on the decay ψ(2S)→π+π-J/ψ, we update the values of coupling constants (gi) and chromopolarizability (аψ(2S)J/ψ) in this process.     

First Evidence of ψ(3770) Hadronic Transition to J/ψπ+π—

Evidence of ψ(3770) decays to a non-DD final state is observed. A total of 6.8±3.0 ψ(3770)→J/ψ→π⁺π^— events are obtained from a data sample of 8.0±0.5 pb^-1 taken at center-of-mass energies around 3.773GeV using the BES-Ⅱ detector at the BEPC. The branching fraction is determined to be BF(ψ(3770)→J/ψ→π⁺π^—)=(0.59±0.26±0.16)%, corresponding to the partial width of Γ(ψ(3770)→J/ψπ⁺π^—)=(139±61±41)keV.     

First evidence of ψ(2S)→Ω-Ω+

The decay ψ(2S)→Ω^-Ω⁺ is analyzed using 14×10⁶ ψ(2S) events recorded by the Beijing Spectrometer Ⅱ (BESⅡ) at the Beijing Electron Positron Collider (BEPC). Based upon events with no missing charged tracks and a satisfactory four-constraint kinematic t, we determine the upper limit for the branching fraction of ψ(2S)→Ω^-Ω⁺ to be 1.5×10⁴ at a 90% confidence level. By including events with one missing charged track, we are able to report the first evidence of an Ω⁺ signal with a statistical signi cance of 3.1|σ. The branching fraction of ψ(2S)Ω⁺ is determined to be (4.80±1.56(stat)±1.30(sys))10⁵.     

Multi-channel Coupling in the Hadronic Decay Process J/ψ→ωπ+π－

The coupling problem of the three different intermediate processes J/ψ→ωf₂(1270),f₂→π⁺π^－ and J/ψ→b₁^±(1235)π⁺,b₁^±→ωπ^± included in the hadronic decay process J/ψ→ωπ⁺π^－ is discussed.The consideration of the coupling effect is very important for measuring the parameters of the resonances f₂ and b₁^± and the helicity amplitude ratios of these reactions precisely.     

Study of J/ψ、γπ0π0 at BES

The decay J/ψ→γπ⁰π⁰ is studied with 7.0×10⁶ produced J/ψ events collected by the Bening Spectrometer(BES) with the tugger mode senseuve to both chmped and neutral final state at the Bening Electron-Positron Collider(BEPC), The evidences for the existence of f_J(1710) and E(2230) in this channel are presented, and the corresponding masses as wen asthe product branching ratios are obtained.     

由ψ(2S)→π+π－J/ψ道测量J/ψ轻子道衰变分支比

利用北京谱仪(BES)上取得的ψ(2S)数据,对ψ(2S)→π⁺π^－J/ψ,J/ψ→1⁺1^－和J/ψ→任意末态两个过程进行了细致的研究,得到J/ψ的轻子道衰变分支比为B(J/ψ→e⁺e^－)=(5.90±0.07±0.16)%和B(J/ψ→μ⁺μ^－)=(5.96±0.08±0.16)%,由此给出Be/Bμ的值为0.990±0.018±0.024.假定Be=Bμ,J/ψ的轻子道衰变分支比为B(J/ψ→1⁺1^－)=(5.93±0.05±0.16)%.上述结果可用来估计强相互作用耦合常数αs和QCD减除参数∧.     

π－π－ Bose-Einstein Correlation at AGS Energies

The study of Bose-Einstein correlations between two identical particles offers a powerful probe to the space-time evolution of ultrarelativistic nucleus collisions.We calculate the correlation function of π^－π^－ due to the four space-time and four-momentum distributions of π-at freeze-out in hadronic cascade simulation of ²⁸Si(14.6 A GeV/c)+Au reactions.The correlation function calculated by Fourier transformation method,the correlation function resulted from fullcalculation and the corresponding experimental correlation function agree each other very well.The above freeze-out configuration of π^－ is also used to calculate the root mean square length of π^－ source.These lengths are compared with the conventional fitted radius parameters of source.     

π－核双电荷交换反应核谱因子和26Mg(π+, π－)26Si反应

π^－核双电荷交换反应的强度与反应过程的两核子转移的核谱振幅直接联系着. 本文讨论了这类反应与它们的核谱因子的关系. 并以²⁶Mg(π⁺, π^－)²⁶Si为例, 用两种核结构讨论了它的激发函数和微分截面. 我们所用的理论方法能够解释实验数据.     

PRODUCTION OF A 3－+ GLUEBALL IN J/ψ RADIATIVE DECAY

The multiple angular-correlation function for the sequential decays J/ψ→γ+G(3^－+), G(3^－+)→M₁M₂, where G is a J^pc=3^－+ state and M₁ and M₂ are spinless mesons, is deduced. A 3^－+ glueball state is discussed and the ratios of the helicity amplitudes of J/ψ→γ+G(3^－+) are calculated. One ratio is independent of the glueball's mass and very small.     

Decay of the J/ψ to Σ0Σ0 Final State

With 7.8 million produced J/ψ events collected by the BES detector at the BEPC, the decay J/ψ→Σ⁰Σ⁰ is analysed. The branching ratio is measured to be BR(J/ψ→Σ⁰Σ⁰)=(0.97±0.04±0.24)×10^－3. The angular distribution is of the form dN dcosθ=N₀(1+α cos²θ) with α value of －0.21±0.27±0.13.     

Contribution of One-Photon Annihilation at ψ(2S) in e+e－ Experiment

The continuum one-photon annihilation at ψ(2S) in e⁺e^－ experiment is studied. Such contributions to the measured final states ωπ⁰ and π⁺π^－ at ψ(2S) mass are estimated by phenomenological models. It is found that these contributions must be taken into account in the determination of branching ratios of ψ(2S)→ωπ0 and ψ(2S)→π⁺π^－, as well as other electromagnetic decay modes. The study reaches the conclusion that in order to obtain the correct branching ratios on these decay modes at BES, at least 10pb^－1of data below the ψ(2S) peak is needed.     

Study of D0→π－l+νl Decay

In this paper, the D⁰→π^－l⁺ν_l decay process is studied by applying light-cone QCD sum rules. The form factor of D→π transition is calculated by choosing a correlation function with a chiral current to eliminate the effect caused by the uncertainty of the twist-3 function of the pion. Therefore the calculated result of the form factor is improved, and the branching ratio of the D⁰→π^－l⁺ν_l decay process is consistent with the new experimental data.     

Measurement of Structure Function of τ→π±2π0v

The structure function of τ→π^±2π⁰v is measured by model independent method. The result is compared with Kuhn-Santamaria model, Isgur-Morningstar-Reader model and Feindt model. Good consistency between data and the three models is shown within the experimental error range. The comparison with the structure function of τ→3π^±v measured by OPAL Collaboration also shows there is no obvious difference within 0.52.     

J/ψ辐射衰变过程中3－+胶子球的产生

本文导出了过程J/ψ→γ+G(3^－+), G(3^－+)→M₁M₂的多重角关联函数, 其中G是J^pc=3^－+的态, M₁和M₂是自旋为零的介子. 本文还讨论了3^－+胶子球态并计算了过程J/ψ→γ+G(3^－+)的螺旋性(helicity)振幅之比. 结果表明, 其中的一个比率与胶子球的质量无关, 其值很小.