2001 Vol. 25, No. 9
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We present here the result of observation of TeV gamma ray emission from the galactic plane at a galactic longitude of 79.3866 deg. With Atmospheric Cherenkov Telescopes (ACT2 and ACT3) located at Xinglong station. The data was taken between Oct. 1995 and Nov. 1998 over a total time of 224.4h in the standard ON-OFF mode. Assuming the data obey Gaussian distribution, a formula of the maximum likelihood ratio λ was derived that gives the probability of significance level directly. Using the formula, we analysed the data and found that there is no evidence for TeV gamma ray emission from the galactic plane within statistic error.
Based on the Ingelman-Schlein model for hard diffractive scattering and the factorization formalism of non-relativistic QCD for quarkonia production, we present a study of associated J/ψ+γ production through single Pomeron exchange approaching Tevertron energy region. It is found that the pT distribution of the cross section is sensitive to the color octet matrix elements. But the ratios of the inclusive production cross section to the single diffractive production cross section are not so. The ratios are sensitive to the product Dfg. The experimental mesurement of this process at the Tevetron would shed light on the nature of the Pomeron and test the diffractive hard scattering factorization.
Annihilation of pp in-flight into π0π0η is an excellent reaction to search for glueballs with quantum numbers JPC=0－+,2－+decaying to π0π0η, and exotic state with JPC =1－+ decaying to π0η. The relativistic tensor formalism of partial wave analysis and some Monte Carlo simulation for this process are presented in this paper.
In this paper, the superposition of the qs-coherent states is constructed, and its nonclassical properties such as squeezing property, antibunching effect are studied. The effects of the superposition coefficient and deformed parameter q and s variables on these nonclassical properties are discussed by making use of numerical calculation. The relevant results of the even and odd qs-coherent states, as special cases, are contained in more general conclusion of this paper.
High spin states in 143Pm have been investigated via the 128Te(19F,4nγ)143Pm reaction using techniques of in-beam γ-spectroscopy. γ-ray singles,γ-γ coincidences, γ-ray anisotropies and DCO ratios have been measured. Based on these measurements, the level scheme of 143Pm has been extended up to excitation energy of 10535.4keV including 32 new γ rays deexciting of 17 new levels. The yrast levels in 143Pm can be understood qualitatively in the framework of a weak-coupling model.
The breakup reaction of neutron rich nucleus 17N on 197Au and 9Be targets has been measured at RIBLL (Radioactive Ion Beam Line at Lanzhou). The product yields and the cross sections of charged particles in pair at forward angles were measured with the 14-unit detector array. The detection efficiency of the detector system was corrected by using Monte Carlo method. The breakup cross sections show that the ratio of the breakup cross section on 197Au to 9Be is 4—5. The cross sections of different breakup channels were also obtained. The results indicate that for a heavy target, except the contribution of nuclear dissociation, the Coulomb dissociation contribution has to be taken into account.
Light charged particles emitted from the reactions of 35MeV/u 40Ar+197Au have been measured. The slope nuclear temperature parameters and the isotope nuclear temperature parameters are extracted from the slope of energy spectra and double isotope yield ratios respectively, and on average, the slope temperatures are slightly larger than the isotope temperatures. The entropy values are extracted also with several methods by using the d/p ratios, d-like/p-like ratios, reduced yields of isotope d and the reduced multiplicities of charged particles Mred, respectively. The entropy values from the reduced yield of isotope d and the reduced multiplicity of charged particles Mred are nearly the same, and these two methods can be used in low beam energy heavy ion reactions. The charged particles emitted in rear angles are mainly from an equilibrium state source with temperature about (4.7±1.2) MeV and entropy S/A=2.5±0.5, from which the Freeze-out density can be deduced. It is nearly but less than 0.1 ρ0.
To check the feasibility of deep inelastic heavy-ion reactions in populating the high-spin states in Z≈56,N≈80 nuclei, a test experiment has been carried out by using the reaction of 410 MeV 82Se+natBa. γ-γ coincidence measurements have been performed using in-beam γ spectroscopy techniques. Population cross-sections of excited states in both target-like fragments and projectile-like fragments have been estimated. New γ transitions were identified in several target-like fragments. A new level scheme including five new levels has been established for 136Ba. The preliminary results show that deep inelastic heavy-ion reactions are very promising for populating the excited states in the Z≈56,N≈80 region.
Particle radiative capture cross sections of 12C(n,γ) and 12C(p,γ) have been calcaulated at 90° in the neutron energy range of 5—25MeV and proton energy range of 8—35MeV. Pigmy resonance exists at the excitation energy Ex=13MeV in 12C(n,γ) reaction. The dips observed at the excitation energy around 11.74MeV and 14.06MeV in 12C(p,γ) reaction are attributed to the destructive interference between semidirect capture and fine resonance capture in the process of doorday state. The calculations agree with expermental results.
Using the new model developed for the light nucleus reactions, the cross sections of the reaction n+16O have been calculated, especially the double differential cross sections of the outgoing neutrons have been calculated. To conserve the angular momentum, the angular momentum coupling effect is taken into account in the preequilibrium emission process. Because of the lightness of target mass, the recoil effect is also taken into account to maintain the energy balance. The fitting of the calculated results and the experimental data shows that this method is successful in calculating the double differential cross section of the light nucleus.
The anisotropy of the azimuthal distributions of the final state particles from nucleus-nucleus collisions is studied within the microscopic transport approach. A clear signature of the azimuthal correlation between directed and elliptic flow is evidenced in the model calculations. It is found that the azimuthal correlation is sensitive to the magnitude and type of transerves flow. The second Fourier coefficients of the azimuthal distribution can be calculated on an event-by-event basis. In order to obtain a statistically relevant measurement, the elliptic flow of the collisions can be determined by further averaging over many events. Using this method of analysis, the influence of the azimuthal dispersion of the estimated reaction plane to the measured results of elliptic flow can be removed.
The two-dimensional uncoupled quartic oscillator was chosen to test the validity of the Berry-Tabor trace formula. Periodic orbits of the system were calculated by integrating Hamiltonian equations of motion on reasonable tori and the curvatures on the energy surface were obtained by carefully constructing the orbits around the reasonable tori. Finally, the value of the semiclassical action function and that of the quantum action function in the case S<30 were compared, and the good agreement between the two functions indicates the validity of the trace formula. On the other hand, in the quantum action function RQM(S,E)-S figuration, that peaks appeared at the action values corresponding to the periodic orbits of the classical system provide rich information on quantum-classical correspondence.
By resolving Tolman Oppenheimer Volkoff equation based on a temperature, density, and isospin dependent nuclear equation of state of nuclear matter, we obtained the mass of neutron star as a function of central density, and the radius of neutron star was also investigated. It is found that both the maximum mass and the radius of neutron star strongly depend on the incompressibility, symmetry energy strength coefficient, and effective mass of nucleon. With the increment of the incompressibility and symmetry energy strength coefficient and the decrement of the nucleon effective mass, the maximum mass of nentron star increases. Meanwhile, the nuclear equation of state with large incompressibility, symmetry energy strength coefficient and nucleon effective mass results in relatively large neutron radius. These results imply that one can get some information about the nuclear equation of state by investigating the macroscopical variables of neutron stars such as mass and radius etc. The relationship of the mass and radius of neutron star is also investigated.
A new approach to studying the condition of onset of dissipation fission is put forward. Based on this approach, the analysis for a large body of data at intermediate and heavy fission system (A>160) indicates that the angular momentum and temperature are the two most basic conditions needed to onset fission delay effect. The data of in nuclei suggests the importance of large angular momentum condition in the case of light fission system.
A method is introduced to measure the trigger efficiency in R scan experiment carried out with BESII at BEPC. The design of trigger table, offline event selection and calculation of efficiency are described. The principle of trigger efficiency measurement is: a data sample for specific physics event type is chosen orthogonally to certain trigger condition at both online trigger level and offline selection level; and then the ratio of number of events in the sample which satisfy the trigger condition to the total number of events in the sample is the efficiency of this trigger condition. The efficiencies of various trigger conditions, trigger channels and event types are given.
A double gap Resistive Plate Chamber (RPC) made of Chinese materials is constructed and tested with cosmic ray. The detection efficiency is close to 100% and the time resolution is around 2ns. The variation of detection efficiency curves and time resolutions in different positions are also given. The results show that its performance can meet the requirement of general particle physics experiment.
In this paper,a study of the radiation damage and re-magnetizing utilization of the permanent magnet wiggler used in the Beijing Free Electron Laser facility is reported. For the radiation damaged wiggler,the magnetic strength can be restored to the original value by magnet re magnetization,arrangement optimization and re assembly. The preliminary experimental result shows that the effective lifetime of the re-magnetized wiggler can be longer than the original wiggler under the same beam radiation condition. Also the mechanism of the magnet damage by radiation and the modification method are discussed.
The design of the BFEL optical cavity's 5-D precise remote-control adjuster is described. This paper discusses the special chracteristic of the FEL cavity,and introduces how to inplement the transfer of the cavity's displacement and angle adjusting inside and outside the vacuum chamber. This optical cavity adjuster is designed with 3 level control precision,its displacement's adjustment range is ±5mm, the resolution is 2μm,the angle's adjustment range is ±3° and the resolution is 0.5″. This control system has been used in BFEL's experiments.
The Disk and Washer (DAW) accelerating structure not only has shunt impedance and high Q value,but also has a high coupling constant between the neighboring cells. At X band,its advantages are especially useful. In this work, a mathematical model used to optimize DAW (without supports) cavities by SUPERFISH was built and the solution was presented. Moreover,the optimization of DAW (with supports) by MAFIA400 was also carried out and the influence of supports was analyzed.
The dispersion curve of the optimized DAW cavities was calculated by URMELT (without supports) and MAFIA400 (with supports),the influence of the supports was studied,and the problem of the overlapping of passband in the accelerating frequency was discussed.
This paper illustrates the measurement principle for constructing Helmhotz coil system by using the magnetic flux method, by which the magnetic parameters of a permanent block can be measured. Also, this paper gives the method of software design based on high precision integrator. If the size of Helmhotz coils is larger enough, the measurement errors coming from the deviations of the block positions can be ignored. With the flux measurement method, the magnetic flux variations between two sample points are not affected by the speed of the step motor, but only related to the space positions of the two sample points. So it reduces the errors coming from the motor vibrations and the speed changes effectively. Using this system, a permanent magnet block used for BEPC mini-β permanent quadrupole has been measured. At last, this paper gives detailed discussions on the system errors arising from the mechanical manufacture deviations and the mechanical installation deviations.
The transmutation of nuclear waste 129I in the subcritical system was studied in the present work using both theoretical and experimental methods. In the experiment, the energetic proton beam (1.0 GeV) form accelerator was used to bombard a thick lead target. And the long lived nuclear waste 129I was transmuted to 130Xe by the spallation neutrons generated in the target. The transmutation efficiency of 129I was compared with theoretical simulation. And the transmutation in an Accelerator Driven Subcritical Fast Reactor (ADSFR) was explored with the experimental results. The spent fuel of PWR (Pressured Water Reactor) is assumed to be used as the fuel in ADSFR. The liquid lead was chosen as target and coolant in the ADS.
A prototype of single cell Multi-gap Resistive Plate Chamber (MRPC) has been made together with the setup of the test system. The property of the chamber has been tested with both the cosmic ray test system and the test beam facility T10 of CERN in Geneva. The time resolution measured is around 70ps. The detection efficiency for minimum ionizing particle is above 95%.
This reply pointed out that the conclusion of 《Comment on “The Proof of Irreducibility Postulation and Its Applications”》 is incorrect.
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