APPROXIMATE B.S. WAVE FUNCTIONS FOR AN ELECTROMAGNETIC BOUND SYSTEM OF SPINS (1/2, 1/2) OR (1/2, 1/2) WITH UNEQUAL MASSES

The Bethe-Salpeter equation for an electromagnetic bound system of spins (1/2—1/2) or (1/2—1/2) with unequal masses are solved in this paper. The approximate B.S. wave functions for these systems are given. Utilising these wave functions, the decay rate and branching ratio for Ξ⁰→(Σ⁺μ^－)+v_μ are calculated with accuracy up to order O(α). The results are wΞ⁰→(Σ⁺μ^－)+v_μ1.12(1/sec) and R=[wΞ⁰→(Σ⁺μ^－)+v_μ]/[wΞ⁰→(Σ⁺μ^－)+v_μ]4.7×10^-7. Similarly, the process Λ→(pμ^－)+v_μ is also discussed.     

QUASI-ELASTIC AND DEEP INELASTIC REACTIONS OF 12C ON 27Al

Quasi-elastic and deep inelastic reactions of 71.5 MeV ¹²C ions on a ²⁷Al target are measured, ΔE-E telescope is used to identify the reaction products. The energy spectra, angular distributions and contour products in the E-θ plane are obtained and discussed.     

The Cross Section Measurement for the Reactions of 48,46Ti(n,p) 48,46Sc 50Ti(n,α) 47Ca and 58Ni (n,2n) 57Ni 58Ni(n,p)58m+gCo

The cross sections for the ⁵⁰Ti(n,α)⁴⁷Ca,⁴⁶Ti(n,p)⁴⁶Sc、⁴⁸Ti(n,p)⁴⁸Sc and ⁵⁸Ni(n,2n)⁵⁷Ni ⁵⁸Ni(n,p)^58m+gCo reactions have been measured by using the activation method relative to the cross sections of the ²⁷Al(n,α)²⁴Na reaction in the neutron energy range of 13.50—14.81MeV.The neutron energies were determined by the cross section ratios of the ⁹⁰Zr(n,2N) ^89m+gZr and ⁹³Nb (n,2n) ^92mNb reactions.The results obtained are compared with the published and to be published data of several authors.     

FINE STRUCTURES OF INCLUSIVE SPECTRA(Ⅰ)——SUM RULES AND THE GENERALIZATION OF FEYNMAN-YANG SCALING

Important implications of the fine structure of inclusive spectra(to be calledinclusive and semi-inclusive spectra of nearby particles,which represent the local dis-tributions of nearby particles in three-dimensional phase space with rapidity y and transverse momenta P_⊥x, P_⊥z as independent coordinates are explained,and some basicfeatures of the fine stucture are found,namely,sum rules and the generalized formof the Feynman-Yang scaling.One of the sum rules,for example,is:where f_(1;k) denotes the normalized invariant inclusive cross section of k closely neigh-boring particles.It follows that the inclusive the spectra of nearby particles arequalitatively different from the usual ones.The generalized form of the Feynman-Yang scaling for the case of k closelyneighboring particles,for example,is:f_(1;k)(s,x₁,P_⊥1,…x_k,P_⊥k⁾∞,（s→∞,x₁≤x₂≤…≤x_k）.where‘∞’denotes‘approaches a definite limit’.For k=2,the existing experimentaldata for the rapidity gap-length distributions show that for FNAL energies,f_(1,k） isalready close to its limiting form.The inclusive（semi-inclusive）spectra of nearbyparticles way be able to reflect effectively short-range correlation effects.     

THE MEASUREMENT OF LIGHT PARTICLE EMISSION FROM 12C+159Tb,Ag AND 89Y REACTIONS

The energy spectra and angular distributions of α-particle emitted from ¹²C-induced reactions with ¹⁵⁹Tb, Ag and ⁸⁹Y targets have been measured. Meanwhile the emitted deutron's angular distributions with ¹⁵⁹Tb and ⁸⁹Y targets and proton's with ⁸⁹Y target have been also obtained.
The α-energy spectra associated with mentioned reactions have bell-like shape with probable energy near coulomb barrier. However, the main characteristic of the α-angular distribution for ¹⁵⁹Tb and Ag targets is peaked at or near the grazing angles. For the case of ⁸⁹Y target, α-differential cross-sections monotonically decrease with angles beyond 40º. The angular distributions of potons and deutrons nearly decrease exponentially.
The measured α-angular distributions could be divided into two components, one coming from α-evaporation is isotropic, another is anisotropic. The anisotropic component may be explained incomplete-fusion process in which the cross-section can be reproduced by a "Sum-Rule Model" due to J.Wliczynski.
In order to explain the anisotropic component of emitted α-particle, we propose in complete fusion model with a strong-damped sticking rotation, in which the rotation angles and interaction time of the composite system are also estimated.     

MEASUREMENT AND ANALYSIS OF EMITTED α PARTICLES IN REACTIONS OF 12C BOMBARDING 12C,27Al AND natCa

The energy spectra and angular distributions of the emitted α particles in the reactions of the 69.5MeV ¹²C bombarding ¹²C,²⁷Al and ^natCa have been measured and analysed using the fast particle exciton model. The contribution from the equilibrium and preequilibrium α-emissions is calculated to be 89%, 81% and 83% of the total α yields for the three reactions respectively, where the preequilibrium α emissions are 11%, 14% and 16% respectively. A small contribution comes from the other reaction mechanism.     

CROSS SECTION MEASUREMENTS OF NUCLEAR REACTIONS FOR Ni INDUCED BY 14MeV NEUTRONS

The cross sections of reactions ⁵⁸Ni(n,2n)⁵⁷Ni,⁵⁸Ni(n,p)^58mCo,⁵⁸Ni(n,p)^58gCo and ⁵⁸Ni(n,p)^58m+gCo were measured based on ²⁷Al(n,a) ²⁴Na reaction by activation methods.Incident neutron energies were 14.10MeV and 14.62MeV.A comparison was made between present results and other published data.The cross sections for ^58gCo nuclei formation are given for the first time.     

Cross Section Measurements for (n,d*)(n,t) and (n,n'α) Reactions

Cross sections for some (n,d*),(n,t) and (n,n'α)reactions have been measured by using the activation method relative to cross sections of ²⁷Al(n,α)²⁴Na or ⁹³Nb(n,2n)^92mNb reactions in neutron energies around 14MeV.In this paper some of the published cross section data have also been listed and compared with our results.The neutron energies were determined by the method of cross section ratios for the reactions of ⁹⁰Zr(n,2n) ^89m+gZr and ⁹³Nb(n,2n)^92mNb.     

The Cross Section Measurements for the 100Mo(n2n)99Mo,96Mo(n,p)96Nb and 92Mo(n,α)89m+gZr Reactions

The cross sections for ¹⁰⁰Mo(n2n)⁹⁹Mo,⁹⁶Mo(n,p)⁹⁶Nb and ⁹²Mo(n,α)^89m+gZr have been measured by using the activation method relative to the cross sections of ²⁷Al(n,α)²⁴Na in the neutron energy range 13.40—14.79MeV.The comparison between the values of measured and calculated using theory mode was made.The evaluated excition functions for the three reactions are given.     

Direct measurement of the resonance strengths and branching ratios of low-energy(p, γ) reactions on Mg isotopes

Proton capture reactions on Mg isotopes are significant in the Mg-Al cycle in stellar H-burning.In particular,the resonance strengths and branching ratios of low-energy resonances in Mg(p,y)26 A1 reactions determine the production of ~(26)Al,which is one of the most important long-lived radioactive nuclei in nuclear astrophysics.In this article,we report our first experiment using the intense proton beam of approximately 2 mA provided by the JUNA accelerator ground laboratory and a new technique that can minimize the composition change of targets under intense beam irradiation.The resonance strengths and branching ratios of E=214,304,and 326 keV resonances in the reactions of ~(24)Mg(p,γ)~(26)Al,~(25)Mg(p,γ)~(26)Al,and ~(26)Mg(p,γ)~(27)Al,respectively,were measured with high accuracy.The success of this experiment provides a good calibration for the nuclear astrophysical experiment at the Jinping underground laboratory.     

SYMMETRY OF THE ROTATION+VIBRATION SPECTRA FOR NUCLEAR MOLECULE 12C+12C

The rotation-vibration spectra of nuclear molecule ¹²C+¹²C is chassified by the irreducible representations of group U(5). It is shown that the symmetry of rotation-vibration levels of nuclear molecule ¹²C+¹²C are discribed by means of dynamical symmetry U(5)U(4)O(4)O(3).     

Study of ψ(2S)Decays into pπ and KK

From a study of(2S)decays into vector-pseudoscalar final states,ρπ and KK*,based on a sample of 1.27×10⁶ produced (2S) events,we have set upper limits at 90% confidence level on the branching fractions into ρπof 3.6×10^－5, into K⁺K^*+c.c.of 2.5×10^－5,and into K⁰K^*0+c.c.of 1.2×10^－4.We find that all these decays are substantially suppressed relative to the corresponding J/ψ decays in comparison with PQCD predictions.Our results confirm the MARK Ⅱ measurements at an improved sensitivity level.     

Measurement of Inclusive Semileptonic Branching Fractions for D－→e－X and D0→e－X

We report a measurement of the absolutely inclusive semileptonic branching fractions of D^－ and D⁰ mesons, using a data sample of 22.3pb^－1 collected with BES detector at BEPC e⁺e^－ Collider at s=4.03GeV and based on the method of "combinative D⁺ and D⁰ single and double tags". The measured values of the branching fractions for D^－→e^－X and D⁰→e^－X are (21.8±8.5±4.2)% and (8.9±3.0±1,6)%, respectively. The measured ratio of the branching fractions is BF(D^－→e^－X)/BF(D⁰→e^－X)=2.4±1.7±0.8.     

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.     

Development of Yangbajing air shower core detector for a new EAS hybrid experiment

Aiming at the observation of cosmic-ray chemical composition in the "knee" energy region, we have been developing a new type of air-shower core detector(YAC, Yangbajing Air shower Core detector array) to be set up at Yangbajing(90.522?E, 30.102?N, 4300 m above sea level, atmospheric depth: 606 g/m2) in Tibet, China.YAC works together with the Tibet air-shower array(Tibet-Ⅲ) and an underground water Cherenkov muon detector array(MD) as a hybrid experiment.Each YAC detector unit consists of lead plates of 3.5 cm thickness and a scintillation counter which detects the burst size induced by high energy particles in the air-shower cores.The burst size can be measured from 1 MIP(Minimum Ionization Particle) to 106 MIPs.The first phase of this experiment, named"YAC-Ⅱ ", consists of 16 YAC detectors each with a size of 40 cm×50 cm and distributed in a grid with an effective area of 10 m2.YAC-Ⅱ is used to check hadronic interaction models.The second phase of the experiment, called"YAC-Ⅱ ", consists of 124 YAC detectors with coverage of about 500 m2.The inner 100 detectors of 80 cm×50 cm each are deployed in a 10×10 matrix with a 1.9 m separation; the outer 24 detectors of 100 cm×50 cm each are distributed around these to reject non-core events whose shower cores are far from the YAC-Ⅱ array.YAC-Ⅱ is used to study the primary cosmic-ray composition, in particular, to obtain the energy spectra of protons, helium and iron nuclei between 5×1013eV and 1016 eV, covering the "knee" and also connected with direct observations at energies around 100 TeV.We present the design and performance of YAC-Ⅱ in this paper.     

Direct surface-transfer reaction to the continuum states induced by a 1760 MeV 40Ar beam on 27Al and natTi target nuclei

The inclusive energy spectra of few-nucleon transfer reactions obtained by bombarding ²⁷Al and ^natTi target nuclei with the GANIL 1760 MeV ⁴⁰Ar beam have been analysed in terms of direct surface-transfer reactions populating the continuum states. The shape at forward angles of the various energy spectra and the corresponding angular distributions are well reproduced by a diffractional model calculation based on mutual excitation of the two residual partners. It turns out that one of the essential ingredients of the calculations is the Williams partial level density either of the target or of the projectile constructed only with the transferred nucleons or residual holes coupled to the ground state.     

MICROSCOPIC OPTICAL POTENTIAL CALCULATIONS OF FINITE NUCLEI WITH EXTENDED SKYRME FORCES

Microscopic optical potential calculations in the Hartree-Fock (HF) approximation with Extended Skyrme forces are investigated. The HF equation is derived from the variation principle and the potential formula of spherical nuclei is obtained by two different ways. Then the calculations for symmetric nuclei ¹⁶O, ⁴⁰Ca and asymmetric nucleus ⁹⁰Zr with eight sets of Skyrme force parameters are presented. Our results show that the potential from and variating tendency with incident energy are reasonable and there apparently appears a "wine-bottle-bottom" shape in the intermediate energy region. Furthermore, our calculations reflect shell effects clearly.     

Measurement of Excitation Function and Analysis of StatisticalProperty in 27Al+27Al mssipative Reaction

The angular distribuhon in the range of 0_cm=50°—90° and excitation funchon of the reachon products in heavy ion dissipahve reachon ²⁷Al+²⁷Al were measured, in the incident energy region from 114MeV to 120MeV with 200keV step. The statishcal property of the fluctuation of the excitation funchon in heavy ion dissipative reaction was discussed based on the integration of the macro outgoing channels.     

THE STUDY OF α-EMISSION INDUCED BY 16O ON 27Al

The α-particles induced by 84.5MeV and 62 MeV ¹⁶O on ²⁷Al are measured using ΔE-E semiconductor telescope. The energy spectra, the angular distributions, the contour plot of d²σ/dE﹒dΩ in the E-θ plane of the emitted α particles and the variation of the nuclear temperature with the emission angles are obtained. The mechanism of the direct α particles is discussed.