1996 Vol. 20, No. 6
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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.
RIBLL1 experimental setup consists of RIB identification system,secondary target control system and secondary reaction products measurement system.The high gain x-y position sensitive PPAC with delay cable grouped readout,the scintillation foil time pickup detector focusing with ellipsoidal surface,the traverse field IC,the large area two dimensional position sensitive scintillatillator with PMT matrix readout,the Compton suppressed HPGe γ-ray detectors and twin longitudinal field iC are major components.This setup has been installed at RIBLL1.The performance measurements and test experiments are in progress.
A beryllium filter detector spectrometer with high efficiency for neutron inelastic scattering has been built beside the horizontal channel of heavy water reactor in China Institute of Atomic Energy.It is the first time to develope a new type of beryllium filter with a wide receiving angle(～30°)and focus arrangement of beryllium blocks.The detecting efficiency of the spectrometer is raised at least by a factor of three.Furthermore,the influence of coherent scattering upon experiments has also been eliminated in the range of low energy.By automatic rotating of different crystal planes of Ge monochromator which possesses particular orientation the measurable energy range of the spectrometer has been widened(from 10 to 400meV)and the energy resolution improved (4%-9%).On this spectrometer,we have measured the optical vibrational modes for ZrH1.6 and PdH0.58 and the total spectrum of the high-temperature superconducting material YBa2 Cu3 O6+x and observed its unusual structural peaks, high frequency modes and anomalous scattering intensities.It has been shown that the spectrometer not only is efficient but also possesses an excellent physical capability.So it is possible to carry out extensive research on inelastic thermal neutron scattering on a medium-flux reactor.
The cross sections of single and double photon production are calculated in both direct and resolved processes in hard photoproduction at HERA in the leading order(LO)of QCD.The results indicate that single photon production is dominated by direct processes while xT≤0.15.The main sources of double photons are the subprocesses of resolved processes gg→γγ and qq→γγ.Under the same condition,the double photon cross section is of the same order as those in h1h2→γγX.The study of double photon production may be helpful for exploring the structure of resolved photon.
By studying the solutions of the reflection equations,we find out a series of integrable supersymmetric systems with different boundary conditions.The Hamiltonian contains four free parameters which describe the contribution of the boundary terms.
The Technicolor(TC)O(αmt2/mw2)corrections to top pair production in high energy e+e－ annihilation are calculated in the one generation TC model.The analytic expressions are given for the form factor, the renormalized matrix element and its square.Numerical examples are presented for the corrections to the total cross-section ,the forward-backward asymmetry AFB and the left-right asymmetry ALR.We found that the corrections can reach －12.3%, －3.3% and －11.7% to the observables,AFB and ALR respectively for the favorable parameter values.The level of these corrections might be achieved at the next-generation linear collider(NLC).It might open a window for testing TC theory.
The next to leading order Debye screening mass in QGP is calculated by taking into accout the damping rate of gluons in the formalism of real time finite temperature QCD,and the infrared singularity in naive calculation is cured without adding to the nonperturbative magnetic screening mass as the cutoff.In addition,the result is shown to be postive and gauge-independent,and is compared with the lattice simulation result.
q-deformed nuclear magnetic moment operatoris defined in terms of rank 1tensor operator of the quantum algebra SUq(2).The results show that the q-deformation parameter depends on valence nucleon number in major shell.The magnetic moments of odd A nuclei with only one valence nucleon outside closed single-j shell are fitted.It shows that in most cases the results are improved in comparison with the Schmidt values.
The relaxation of the isoscalar giant monopole resonance (GMR)in hot nuclei produced in heavy-ion reaction is discussed in the frame of the Boltzmann-Nordherin-Vlasov equation.The oscillation of the GMR in the spherical hot nuclei is isotropic.The calculated GMR energy is approximately equal to that resulting from the formula EGMR=80A－1/3.The nucleon collision as well as the particle escape are the dominant reasons of the relaxation of the GMR in the hot nuclei.
The rotational spectra formula for superdeformed bands is derived from the cranking Bohr-Mottelson Hamiltonian proposed by us.Level spins and transition energies of 24 superdeformed bands in the A～190 region are studied with this formula.The obtained results are satisfactory.
The formulas for calculating the photon transmission coefficient and the capture cross section of the isomeric state for the compound nucleus reaction are presented,in which statistical and non-statistical processes are all contained.Calculating the photon transmission coefficient by solving the cascade deexcitation processes,the (n,γn)processes are deducted reasonably,and the contribution of the first transitions to the levels distributed above the neutron separating energy Bn can be included.The numerical calculations for 59Co and 103Rh in the energy below 4MeV are made.The different calculation methods for the photon transmission coefficients are compared with other and the calculation results of the isomeric capture cross sections are compared with the experimental data.Analysis and discusions,especially the dependence of calculated results on energy level distributions are presented.
A bunched beam for Free Electron Laser(FEL)driven by a linac always encounters some beam-pipe size changes in its transport process.In this paper,the formulae are derived for calculating the equilibrium field energy of a bunched beam and its difference in two pipe sizes by using a space charge cylinder model.The calculations show that a great difference between the results of space charge cylinder model and continuous beam model used before.
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