THE COULOMB DISINTEGRATION CROSS-SECTION AND DECAY RATE OF THE SPIN (0－3/2) ELECTROMAGNETIC BOUND SYSTEM

In this paper, the coulomb disintegration cross-section and decay rate of the atom (π⁺Ω^－) are calculated by using perturbation expansion of the quantized composite field theory and relativistic B-S wave function for spin (0－3/2) electromagnetic bound system. The disintegration cross-section of the high energy atom (π⁺Ω^－) in screened coulomb field of nuclei is about σ=Z^4/3×2.9×10^－18cm², and the calculation result of the decay rate is w[(π⁺Ω^－)→π⁺Λ⁰K^－]/w[Ω^－→Λ⁰K^－]=1+O(α).     

First Observation of 131Pm Decay

¹³¹Pm nucleus was produced in the ¹⁰⁶Cd (³²S,3p4n) ¹³¹Pm reaction. Theproducts were transported by helium jet and tape system, and X,γ single spectra and X-γ,γ-γ coincidence spectra were measured. The half-life of ¹³¹Pm has beendetermined to be (6.3±0.8)s. A partial decay scheme of ¹³¹Pm is proposed.     

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.     

β-Delayed Proton Decays of 133Sm and 149Yb

¹³³Sm was produced via fusion evaporation in the reaction ⁴⁰Ca+⁹⁶Ru. Its β-delayed proton decay was studied by means of “p-γ” coincidence in combination with a He-jet tape transport system, including half-lives, proton energy spectra, γ-transitions following the proton emissions, and the branching ratios to the low-lying states in the grand-daughter nuclei. The possible spins and parities of ¹³³Sm were extracted by fitting the experimental data with a statistical model calculation. The configuration-constrained nuclear potential energy surfaces of ¹³³Sm were calculated by using the Woods-Saxon Strutinsky method. Comparing the experimental and calculated results, the spins and parities of ¹³³Sm were assigned to be 5/2⁺ and 1/2^－, which is reconciled with our published simple (EC+β⁺) decay scheme of ¹³³Sm in 2001. In addition, our experimental data on the beta-delayed proton decay of ¹⁴⁹Yb reported in Eur. Phys. J., 2001, A12: 1—4 was also analyzed by using the same method. The spin and parity of ¹⁴⁹Yb was assigned to be 1/2^－.     

(EC+β+) decay of 130Pm and 128Pr

¹³⁰Pm and ¹²⁸Pr were produced by irradiation of ⁹⁶Ru with ³⁶Ar, and studied using a He-jet recoil tape transport system. Based on X-% and %-% coincidence measurements, the (EC+ # ⁺) decay scheme of ¹³⁰Pm was proposed for the first time and the (EC+ # ⁺) decay scheme of ¹²⁸Pr was revised.     

(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 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.     

J/ψ Physics at BES

Based on 9.0×10⁶ J/ψ data collected at BES, a systematic physics analysis has been Performed. We confirmed the existence of ξ(2230) in J/ψ→γKK and observed for the first time the non-strange decay modes ξ(2230)→π⁺π^－,π⁰π⁰,and pp. The resonance and polarization parameters of f₀(980) and f₂(1270) were measured. The moment stUdy on J/ψ→γK⁺K^－ revealed that the controversial f_J,(1710) is composed of two states, a 0⁺⁺ and a 2⁺⁺. With the help of PWA method, the spin-Parities for η(1440) and f₀(1500) were obtained, and their main decay modes were found.     

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.     

A NEW TRANSITION BRANCH OF THE 5.2 SEC ISOMER IN 183W

During the bombardment of 14.8MeV neutron on natural wolfram samples a γ-ray with energy 291.7keV and halflife 5.17±0.03 sec is observed. From the experimental facts it is assumed that in addition to the two well known transition branches from the decay of 5.2 sec isomer in ¹³⁸W there exists another 11/2⁺11/2[615]→5/2^－3/2[512] isomeric (E3) transition. The hindrance factor of this new transition is calculated. It is well cosistent with the general empirical rule of k^－ forbidden isomeric transition.     

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.     

First decay study of the new isotope <Superscript>129</Superscript>Pm near the proton drip line

The very neutron-deficient nuclide ¹²⁹Pm was produced via the ⁹²Mo(⁴⁰Ca, p2n) reaction and identified for the first time by using the X- coincidence in combination with a He jet tape transport system. According to the decay curve of a 99 keV -ray which corresponds to the known transition in the daughter nucleus ¹²⁹Nd of the ¹²⁹Pm decay, the half-life of ¹²⁹Pm was determined to be 2.4(9) s. Based on the nuclear potential energy surface (PES) calculations, the ground-state spin-parity of ¹²⁹Pm was predicted as 5/2^- which is favorable to feed a 5/2^- low-lying state in the daughter nucleus ¹²⁹Nd via the (EC ) decay.Received: 20 November 2003, Revised: 7 January 2004, Published online: 29 June 2004PACS: 23.40.Hc Relation with nuclear matrix elements and nuclear structure - 21.10.Hw Spin, parity, and isobaric spin - 24.10.Pa Thermal and statistical models - 27.60. + j      

ΛΛ,ΛΛγ and ΛΛπ0 Productions in J/ψ Decay

The channels of J/ψ decay into,ΛΛ,ΛΛγ and ΛΛπ⁰ are analyzed with 7.8×10⁶ J/ψ events collected by BES detector at BEPC Collider.The branching ratios for three channels and the angular distribution for the first channel are measured.The branching ratios are Br(J/ψ→ΛΛ)=(l.08±0.06±0.24)×10^－3,Br(J/ψ→ΛΛγ)－4(90% CL)and Br(J/ψ→ΛΛπ⁰)=(2.3±0.7±0.8)×l0^－4 respectively. The angular distribution for J/ψ→ΛΛ is dN dcosθ=N₀(1+αcos²0),α=0.52±0.33±0.13.     

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.

     

Experimental Study of Resonance f2(1270) in the J/ψ Hadronic Decay

Based on the 2.5 million J/ψ's collected by the BES at BEPC,through the hadronic decay J/ψ→ωf₂(1270),f₂(1270)→π⁺π^－,ω→π⁺π^－π⁰,the properties of the resonance f₂(1270) are studied:its mass,width,and branching ratio.the angular distribution is fitted with maximum likelihood methood,determining its.J^PC=2⁺⁺ and giving in the first time the helicity amplitude ratios of this process as:x=0.99±0.29; y=－0.24±0.17; z₁=0.90±0.57;z₂=0.56±0.22.     

Neutral Higgs Effects on Rare Decay B→Xsl+l－ in the T2HDM

We calculate the new physics contributions to the branching ratios of the rare decays B→X_sl⁺l^－(l=e,μ) induced by neutral Higgs bosons loop diagrams in the top quark two-Higgs-doublet model (T2HDM). From the numerical calculations, we find that (a) the neutral Higgs boson's correction to B→X_sl⁺l^－ decays interferes constructively with its standard model counterpart, but small in magnitude; (b) the neutral Higgs contributions to the branching ratio of B→X_sl⁺l^－ decay can be neglected safely if their masses are larger than 100GeV and tanβ≤40.     

First Study of Weak (EC+β+) Decay Branch for the Neutron-Deficient Isotoep 209Fr

²⁰⁹Fr has been produced by irradiation of ¹⁹⁷Au with ¹⁶O from SFC accelarator uia the fusion-evaporation 4n channel.The(EC+β⁺)decay of ²⁰⁹Fr has been studied by a He-jet tape transport system.The decay scheme is proposed for the first time based on γ-t,X-γ-t,γ-γ-t coincidece and γ-γ delay coincidence measurements,which takes account of 20 observed γ ray.Five members of low-lying states in ²⁰⁹Rn can be explained by the multi-plet [(²¹⁰Rn2⁺)(νf_5/2)^－1].The branching ratio for(EC+β⁺) decay of ²⁰⁹Fr has been estimated experimentaly to be(3.0±1.5)%.     

Structure Analysis of the l/η(1440)

By an amplitudes analysis of the KKπ system in the J/ψ radiative decay to the K⁺K^－π^O and the K⁰_SK^±π⁺ final states, we find that there is one 0^－+ resonance (M=1467±3MeV,Γ=89±6MeV) and two 1⁺⁺ resonances (M=1435±3MeV,Γ=59±5MeV and M=1497±2MeV,Γ=44±7MeV), Which are consistent with the η(1440), the f₁(1420), and the f₁(1510).     

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.     

Branching ratio of rare decay B0(Bs)→γνν

The three-body decay B⁰(B_s)→γνν can occur via penguin and box diagrams in the Standard Model (SM). These channels are useful to determine the decay constant f_B (f_Bs) and B (B_s) meson wave function. Using the B meson wave function determined in hadronic B (B_s) decays, we calculate and get the branching ratio of order 10^－9 and 10^－8 for B⁰ and B_s decay, respectively. They agree with previous calculations.