(EC+β+) Decay of 130Pm and 128Pr

¹³⁰Pm and ¹²⁸ Pr were produced by irradiation of ⁹⁶Ru with 171MeV ³⁶Ar beam,and a He-jet recoil tape transport system transported radioactivities to shielded reigon. Based on X-γ-t and γ-γ-t coincidence measurements ,the (EC+β⁺)decay scheme of ¹³⁰Pm was proposed for the first time and the (EC+β⁺)decay scheme of ¹²⁸Pr was revised.     

(EC/β+) Decay of 130Nd and 140Tb

Isotopes,¹³⁰Nd and ¹⁴⁰Tb were produced using enriched targets ⁹⁶Ru and ¹⁰⁶Cd, respectively,bombarded by ³⁶Ar ion beam. The two nuclides were identified and studied by a He-jet tape transport system in combination with "X-γ" and "γ-γ" coincidence measure- ments. The half-life of ¹³⁰Nd was determined to be (13±2)s. The EC/β⁺ decay scheme of 130Nd was proposed for the first time, and the spins and parties of the ground-state and observed low-lying states in the daughter nucleus ¹³⁰Pr were speculated tentatively. The previous simple EC/β⁺ decay scheme of ¹⁴⁰Tb was revised, and the spin-parity of its groundstate was assigned to be 7⁺.     

(EC+β+) Decay of 133Sm and 1.1s Isomer of 133Pr

By irradiation of an enriched target of ⁹⁶Ru with ⁴⁰Ca and using a helium-jet fast tape transport system in combination with X-γ and γ-γ coincidence measurements,the very neutron deficient isotope ¹³³Sm was produced and studied. A simple(EC+β⁺) decay scheme of Sm is proposed for the first time. A by product ¹³³Pr was produced simultaneously because of the ^98－102Ru contents of the ruthenium target. The half-life of an 11/2^－ low-lying isomeric state in ¹³³Pr has been measured to be (1.1±0.2)s. Using single-particle model,the reduced transition probabilities of the 11/2^－ isomers in ^{131,133,135,137}Pr are extracted from their experimental half-lives and compared with the Weisskopf estimate.     

EC/β+ decay of six medium-heavy nuclei

Previous experimental results of (EC+β⁺) decay for the medium-heavy nuclei reported by our group since 1996, including ¹⁵³Er, ¹⁵⁷Yb, ²⁰⁹Fr, ¹²⁸Ce, ¹³⁰Ce, and ¹²⁸Pr have been briefly summarized. The observed low-lying states in their daughter nuclei have been reviewed in a systematic way and compared with different model calculations. Finally, some questions have been put forward for further study and discussion.     

Measurement of β+ Delayed α Decay of 20Na

Through the ²⁰Na β^{+ 20}Ne→¹⁶O+α process,the half-life and β⁺ delayed α decay spectrum of ²⁰Na have been measured on the Radioactive Ion Beam Line in Lanzhou(RIBLL). The ²⁰Na was identified through TOF-ΔE method and alpha particle was measured by four Si(Au) surface barrier detectors. The half life of ²⁰ Na is(459±7)ms. Result shows that in addition to nine high excitation energy levels with E_d≥2.688MeV, three low excitation energy levels of ²⁰Na with E_d=0.890 & 1.054,1.991,2.424 & 2.457MeV were observed in the experiment. The relative intensity for 1.991MeV level, a more important energy level in the center of mass system energy region from 1.6 to 2.5MeV obtained in this experiment is much higher than the existed one. We also obtained the relative intensities of the levels of E_d=0.890 & 1.054,2.424 & 2.457MeV.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

A Study of the Processes of e+e－→e+e－,μ+μ－ at Large Angle and Measured Luminosities

Using the BES data collected at √S=4.03GeV.the QED processes of e⁺e^－→e⁺e^－,μ⁺μ^－ have been studied. Our measurements agree with the QED prediction,and luminosities obtained from these two final states are compatible at a level of 4%.The total integrated luminosity of 23.1pb^－1 was given for all data collected at this energy region from the calculation.     

Study on Stiffness of the Symmetry Energy at High Densities by π－/π+ Ratio

using the isospin–and momentum–dependent transport model, for three different symmetry energies, we have calculated the π^–/π⁺ ratio as a function of time and tranverse–momentum in central 132sn+124 sn collision at e_beam/A=400mev. the results show that the π^–/π⁺ ratios is very sensitive to the stiffness of the symmetry energy. thus we can probe the stiffness of the symmetry energy at high densities by using the π–/π+ ratio at different time or transverse momentum more accurately than before. comparing experimental data with the calculations will reveal crucial information about the stiffness of the symmetry energy more accurately.hadronic transport model, symmetry energy, π–/π+ ratio     

Systematic study of the K+/π+ ratio and hadronic transport model for rescattering of pion

The proposed hadronic transport model for rescatterting of pion is used to investigate the K+/π+ ratio in p+p,p+Au and Si+Au reactions at AGS energy(14.6AGeV/c).Experimental evidence of increasing continuously of the K⁺/π⁺ ratio from p+p to p+Au to Si+Au at similar incident energy per nucleon is reproduced reasonablely.The experimental fact of K⁺/π⁺ ratio at CERN energy is comparable with corresponding result at ACS energy,is reproduced as well.     

Analytic Approximation for Process e++e－→τ++τ－ Cross Section Near Threshold

In the structure function approach,we calculate the threshold behaviours for e⁺+e^－→τ⁺+τ^－,which including QED radiative corrections from initial correction,vacuum polarization effect,Coulomb effect and final state correction.This theoretical prediction for threshold behaviours of τ-pair production is useful for BES new measurement of lepton τ mass.     

β-Delayed Proton Decay of 93Pd

The β-‘waiting point’nucleus ⁹³Pd has been produced via ⁵⁸Ni(⁴⁰Ca,3n2p) reaction. A helium-jet fast tape transport system was used in combination with p-γ coincidence measurement to identify the β-delayed proton precursor ⁹³ Pd, whose half-life has been measured to be 1.3±0.2s. The measured energy spectrum of β-delayed protons and relative branching ratios to the final states in the daughter nucleus ⁹²Ru are fitted by a revised statistic model calculation, and then the ground state spin of ⁹³Pd are assigned to be 9/2. Meanwhile, a nuclear energy-potential-surface (EPS) calculation is performed by using the Woods-Saxon Strutinsky method. The calculated result supports the ground state spin and parity of 9/2⁺ assignment.     

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.     

A note on Ξc(3055)+ and Ξc(3123)+

The Babar Collaboration announced two new excited charmed baryons Ξ_c(3055)⁺ and Ξ_c(3123)⁺. We study their strong decays assuming they are D-wave states. Some assignments are excluded by comparing our numerical results with the experimental values of the total widths of Ξ_c(3055)⁺ and Ξ_c(3123)⁺. We also suggest some possible decay modes, which will be helpful to