Experimental Study on 22Na(p,γ)23Mg Reaction

The reaction of ²²Na(p,γ)²³Mg has been investigated at the Radioactive Ion Beam Line in Lanzhou(RIBLL) using a radioactive beam ²³Al. The β⁺ delayed proton decay spectrum has been measured with the TOF-ΔE method and zero degree detectors. The half life of ²³Al is determined to be T_1/2=(476±45)ms by using a time scaler combined with the precision pulse generator,which is consistent with the other group's result of (470±30)ms. The known β⁺ delayed protons at E_r=0.216,0.278,0.438,0.479MeV have also observed in the experiment. The resonance strength of isospin analog state (IAS) is calculated. The resonance intensity of IAS is (11.4±6.0)meV. A new energy level of β⁺ delayed proton decay has been identified at E_x=8.916MeV,and their relative intensity also been obtained.     

A New Heavy Neutron-rich Isotope 238Th

A new nuclide ²³⁸Th has been produced via multinucleon transfer reaction induced by 60MeV/u ¹⁸O ion irradiation of natural uranium. The thorium was radiochemically separated from the mixture of uranium and its reaction products. The activity of thorium was measured by using a HPGe detector and a planar HPGe detector. The ²³⁸Th has been identified for the first time by measuring the growth and decay of the γ-rays from its daughter ²³⁸Pa. The half-life of 238Th was determined to be (9.4±2.0)min. In addition,a new (89.0±0.3)keV γ-ray with T_1/2=(8.9±1.5)min was observed and assigned to ²³⁸Th decay based on the measurement of transition energy and half life.     

Experimental Measurements for the QEC-Value of 183Os-Decay

Activities of ¹⁸³Os were produced by 39MeV α particles bombarding on a natural tungsten target.β⁺ spectrum with coincidence gate set on the strongest 382keV γ-rays of ¹⁸³Os decay was measured.The endpoint energy of the β⁺ spectrum was determined and the Q_EC value of ¹⁸³Os decay was extracted to be 2.24±0.10MeV which is in good agreement with the predicted value 2.30±0.10MeV on the basis of mass systematics.     

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).     

Observation of Heavy Cluster Emission From Radioactive 230U Nuclei

230Pa was produced with the reaction ²³²TH (p, 3n)230Pa in the irradiation powder targets of ThO₂ with 35 MeV Proton beam. Sources of ²³⁰Pa -²³⁰U were prepared by radiochemical method. Using solid-state track registration detectors, two events of ²³⁰U decay with heavy cluster emission have been observed. The preliminary branching ratio to decay comes out to be B=λ_Ne/λ_α=(1.3±1.8)×10^－14.     

Measurement of J/ψ→ηcγ at KEDR

We present a study of the inclusive photon spectra from 5.9 million J/ψ decays collected with the KEDR detector at the VEPP-4M e⁺e^－ collider. We measure the branching fraction of radiative decay J/ψ→η_cγ, η_c width and mass. Our preliminary results are: M(η_c)=2979.4±1.5±1.9 MeV/c², Γ(η_c) = 27.8±5.1±3.3 MeV, B(J/ψ→η_cγ)=(2.34±0.15±0.40)%.

     

First Experimental Determination of Half-Life for New Nuclide 65Se

By using experimental data obtained from the measurement of beta-delayed proton decay of ⁶⁵Se produced in ⁴⁰Ca(²⁸Si,3n)reaction,the absolute detection efficiency of particle telescope for rotating radioactive source was imitatively calcu-lated.The half-life of ⁶⁵Se was thus accurately determined to be 9.6_-4.1^+5.3 ms.The β-delayed proton energy of ⁶⁵Se was 3.70±0.08MeV.The partial decay scheme of ⁶⁵Se β-delayed proton decay was revised and proposed.     

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.     

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)%.     

THE DETERMINATION OF ENDPOINT ENERGY FOR 235Th β-DECAY

Sources of ²³⁵Th were prepared by 14MeV neutron irradiation of Uranium and radiochemical separation.The β-spectra and γ-spectra were measured.The endpoint energy for ²³⁵Th β-decay was obtained to be 1.44±0.04MeV.Thus Q_B of ²³⁵Th was determined to be 1.47±0.07MeV.     

About Three-Body Exit Channel in the Reaction 12C+16O at EL(16O)=56MeV

Three-body exit channel in the reaction ¹²C+¹⁶O at 56MeV has been studied by using measurement of the coincidence between the two changed particles.The projected spectra of the coinsidence between the two α-particles shows that the channel α+²⁴Mg is the main intermediate process of three-body exit channel α₁+α₂+²⁰Ne in the reaction ¹²C+¹⁶O at 56MeV.The analysis of theoretical calculation showed that the sum of sequential decay and statistical break-up fit the experimental spectra satisfactorily.     

Study of Excited States in Neutron-Deficient 197Bi

High-spin states in ¹⁹⁷Bi were populated by bombarding natural Re target and isotope ¹⁸⁷Re target with ¹⁶O beam of 100 MeV. Using comprehensive γ-γ-t coincidence measurements,three new isomers in ¹⁹⁷Bi were established and eleven new y-transitions were identified,while errors in the existing level scheme were corrected.From the level structure systematics of the odd-mass Bi isotopes, the configuration and decay properties of a new isomer with t_1/2n=19.3±4.9ns in ¹⁹⁷Bi were discussed.The y-ray angular distributions were also measured.A new level scheme of ¹⁹⁷Bi was proposed.     

The Decay Scheme of 175Er

The ¹⁷⁵Er activity was produced via the reaction ¹⁷⁶Yb(n,2p) ¹⁷⁵Er by 14MeV neutron irradiation of a natural ytterbium metal target with a thickness of～80mg/cm2.X-γ and γ-γ coincidence measurements were employed to identify ¹⁷⁵Er activity.The half-life of ¹⁷⁵Er has been determined to be (1.2±0.3)min. Eight new gamma rays were assigned to the decay of ¹⁷⁵Er. A partial decay scheme of ¹⁷⁵Er has been proposed for the first time, from which a ground rotational band has been assigned to ¹⁷⁵Tm.     

MEASUREMENT OF ISOMERIC CROSS-SECTION RATIO IN 133Cs(n,γ) 134Cs REACTION

The isomeric absolute cross-section have been measured for the reaction ¹³³Cs (n,c) ¹³⁴ Cs at 14.8 MeV neutron energy.The results are:σ_n,γ^134mCs=1.76±0.14mb;σ_n,γ^134gCs=5.17±0.41mb;σ_n,γ^134+gCs=6.93±0.55mb.The isomeric cross-section ratio is σ^134m_Cs/σ^134gCs=0.34±0.03 The experimental results are in agreement with the values given by S.M. Qaim andcompared with the theoretical results calculated by Huizenga-Vandenbosch theory.From this, the spin cut-off paramenter σ and the number of γ-Cascades have been de-termined.     

Measurement of Reaction Cross Section for 17C and Finite-Range Glauber Model Analysis

We have measured the reaction cross section σ_R of ¹⁷C on the carbon target at the intermediate energy of 97A MeV by using transmission method.finite-range Glauber model has been employed to investigate the density distribution of ¹⁷C by fitting the present result and the previous result of interaction cross section σ_I.By contrast with the result from the analysis of σ_I,a tail in the neutron density distribution of ¹⁷C is found necessary to interpret the present result.Considering the configuration of the valence neutron,a dominant 1d_5/2(77±21%)occupancy is found,which is in agreement with results of momentum distribution measurements.     

New Neutron-Rich Nuclide 185Hf

New neutron-rich nuclide ¹⁸⁵Hf has been identified for the first time.The ¹⁸⁵Hf was produced via the ¹⁸⁶W(n,2p)¹⁸⁵Hf reaction by 14MeV neutron irradiation of natural metallic tungsten powder and separated by radiochemical methods.The identification of ¹⁸⁵Hf was based on the observation of decay γ-ray of its daughter ¹⁸⁵Ta.A half-life of 3.5±0.6min was determined for ¹⁸⁵Hf by fitting the measured growth and decay curve of the 177.59keV γ-ray which is the strongest decay γ-ray of ¹⁸⁵Ta.In addition,a new γ-ray of 164.5±0.5keV was found and assigned to ¹⁸⁵Hf.     

Measurement of the τ Polarization Asymmetry in τ→a1 v→π±π0π0v Decay at Z0 Peak

The τ polarization asymmetry in τ→a₁v→π^±π⁰ π⁰v decay at Z⁰ peak is measured using data collected by L3 detector at LEP in 1992 and 1993, A_pol=－0.239±0.126±0.100, where the first error is statistical and the second systematic. And the effective electroweak mixing angle sin²θ_w=0.2197±0.0219 is derived.     

SOME CONJECTURES ON THE MASS FORMULA OF CHARGED LEPTONS

In this note we propose that the electromagnetic self energy of lepton may beconnected with quantum number n by（ （δm）/m）=（1/（2π））n^-b ,in which b is a constant.Wefnrther propose that the cut-off value of momentum M is connected with gravitationalconstant κ and fine structure constant α by M=（1/√κ）αe^-1-b.So we obtainthe mass formula of charged leptons M=（1/√κ）α exp{-3/4-b-(1/3α)n^-b}.By using the masses of e^- and μ^- and the value of a as in put,we get the calculatedvalues of κ=（6.67231±0.00026）×10^-8cm³g^-1sec^-2and m_r=（1782.306±0.078）MeVwhich agree very well with experimental values κ=（6.6720±0.0041）×10^-8cm³g^-1sec^-2 and m_τ=(1782_-4⁺³)MeV respectively.The mass of the fourth charged leptonpredicted by the formula should be m=（11725.47±0.51）MeV,which can be checkedby experiments in the near future.We also discuss briefly the proposed formula andthe obtained results.     

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.     

Angular distributions of light projectile fragments in deep inelastic Pb + Em interactions at 160 A GeV

The nuclear emulsion was exposed at CERN by the lead projectile at 160 A GeV. The angles between any pair of fragments with Z = 2-4 have been measured in the emulsion plane for the events which did not contain heavy fragments. The constant characterizing the normal angle (J) distribution of the fragment momentum projection onto the emulsion plane with respect to initial projectile momentum p₀ is found to be C_J = (0.37 - 0.02) mrad. Corresponding value C₀ = (121 - 6) MeV/c of nucleon momentum distribution in the lead nucleus coincides with that expected from Fermi momentum distribution for this nucleus. The peak in the pair-angle distribution of double-charged fragments, ⁸Be M 2!, is presented for the region of small angles (<0.1 mrad). The fraction of !-particles coming from the decay of the ground state ⁸Be is found to be (13 - 2)% of their whole number.