1982 Vol. 6, No. 6
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Introducing hard quark scattering mechanism in hadron-hadron interactions of1015--1016 eV region, the propagation of cosmic rays through atmosphere is simulatedby using Monte-Carlo method. The results show that the qualitative features of "two-cluster" events observed in emulsion chamber experiments can be described qualitativelyby the large pr hadron jets produced in quark-quark scattering. But compared with theexperiments, the event rate obtained by us is rather small and the distance between twoclusters is too narrow. Some discussions for the characteristic of largs transverse mo-mentum phenomena in ultrahigh energy region and for improving model are given.
A high sensitive neutron monitor is described in this paper. It has an approxi-mate counting rate of 20 cpm for natural background neutrons. The pulse amplituderesolution, sensitivity and directional dependence of the monitor were determined.This monitor has been used for natural background measurement in Beijing area dur-ing passed year. The yearly average dose is given and compared with the results ofKEK and CERN.
The reason of the rate-dependent breakdown phenomena for higf flux operation ofGMSC, is probably due to the argons' metastable states Arm, and lu or Ou- states ofAr2*, accumulating in "depletion region" on the anode wire HV6, and raising, a rapidcharge generation process in high concentration region of Arm and Ar2. Our calcula-tion is in accord with experiment.
Two scintillation hodoscopes with the same dimension (50×50×0.5 cm3) but dif-ferent shape of light guide have been built with the scintillator type ST 401. Analysing the amplitudes of outputs from four photomultlpliers, the position ofincident particles is definite. The effect of the two shapes of light guide on the posi-tion resolution has been studied. The position resolution of the better one is ±2 cmto ±4cm.
In this paper the beam transverse motion of the RFQ structure are discussed. Amethod for the calculation of the transverse, acceptance ellipse parameters is proposed.Finally the space charge effects and the RFQDYNA program are introduced briefly.
The decay rate of a four-particle decay of the di-exotic atom (π土μ干) is calculatedby using perturbation expansion of the quantized composite field theory. The resultis compared with the decay rate of a free muon.
The effect of hadron structure on the rate of proton decay caused by baryon-num-ber violatng interantion in the SU(5) grand unified theories is considered. The protonlifetime is calculated using an improved translational invariant bag model. We dealwith recoil effect in the decay process properly and thus overcome some problems exis-ting in the popular bag model calculations, for example, "overestimating the wave func-tion overlaps" and adding "a form factor to describe the high momentum suppres-sion". Our result is consistent with recent experiments and can undergo further ex-perimental test. We obtain τp=1.39×1031 yr, for Mx=4.2×1014GeV.
The major purpose of the present paper is to study medium energy (γ, p) reactionmechanisms. Differential cross section calculations are performed in a picture whichincludes both direct reaction process and an excitation of △-isobar-hole states. It isshown that simple PWIA calculation can not give a good fit to the data, but the △-hresult is in reasonable agreement with experiment. This means that the role of △ in-termediate excitation in the. (γ, p) reaction is significant. Some discussions about ob-tained results are also given in the paper.
In this paper, a two-nucleon absorption model for pions at rest is extended todiscuss the nucleon spectra after absorption of pions of a few nundred MeV energies.Nucleon spectra emitted afte 220 MeV pion absorption by 12C, 58Ni and 181Ta are cal-culated. The A dependences of the absorption cross section, the mean number ofnucleons N emitted after pion absorption and the ratio of the yields of protons from π+ v.s. π absorption can be well described by two-nucleon mechanism.
Possible filling up of the high dimensional representations of SU(3) by baryoniais discussed. Characteristics of mass spectra of nucleonium and it's nearest neighbors inthese representations, especially the isotopic rotational band of nucleonium in the repre-sentation (27), are presented. There may be some extremly narrow resonances with massless than 2.6 Gev and width less than 0.1 MeV.
We have measured the angular distributions of fission fragnents for a series ofcompound nuclei formed in the bombardment of 181Ta, W, Re, Pt, 197Au, Pb and 209Biby 72.7, 69.6, 67.4, 65.4, 63.4 and 61.4 MeV 12C ions with mica track detectors. Thecritical angular momentum lcr. can be determined directly from the statistical analysisof the fission fragment angular distribution corresponding to the fission events withfull momentum transfer. The complete fusion cross section σfu were calculated on thebasis of the sharp cut-off model. The results for lcr obtained by this method were com-pared with those predicted by R. Bass model. The published data on fission fragmentangular distributions of 14N+Pb and 12C+238U reactions were also analyzed by thismethod. The values of σfu are found to be in good agreement with the direct comple-te fusion cross section measurements.
In the framework of the eikonal form of the DWIA and by using the transitiondensity method, the differential cross sections for 18O（π, π） 18O（2+, 1.98 MeV） inelas-tic scattering at Tπ=180 and 230 MeV are calculated. The ratios of the integratedeross sections for π- vs. π+ bombardments are analyzed and the effects of changing theneutron radius to the differential cross sections are studied as well. Our results fitthe date qualitatively.
In this paper, a ∧-N effective interaction of Volkov type is introduced with Har-tree-Fock method in multi-center shell model. The results for binding energies of 13Cand 9Be are satisfactory. Comparing with the effective potentials which are mentionedas results of fitting the data of 1-p s-wave scattering, the p component in ∧-N interac-tion is weaker than s-component by 1/3 at least. Moreover, majorana force is impor-tent but model-dependent.
A rotation-vibration model for nuclear molecule is proposed in order to explain theintermediate structures in 12C+16O reaction system.
According to principle of "uniform magnetization", using harmonic analysis me-thod, two dimensional fields for permanent multipiece linear array system are analy-sed, the precise analytical expressions. are given. To make use of these expressions,amplitude of fundamental component and higher order harmonics of two dimensionalfields can be calculated.
From nuclear individual α-cluster model and by using plane, wave impulse approxi-mation, we have discussed the quasi-free scatterings p-12C (p,pα) and p-16O (p,pα) atintermediate energies. The wave function of the individual α-cluster has expanded asa superposition of the Harmonic oscillator wave functions. The paremeters of Har-monic oscillator are determined by fiting the nuclear charge form factor obtained fromelectron-nucleus scattering experiments. The calculated result shows thet the use ofthe α-cluster wave function can give a theoretical quasi free cross section which agreesbetter with the data.
This method can be used to measure the wire tension of multiwire propotional cham-bers and drift chambers, Before or after the chambers have been sealed, using sim-ple instruments and according to the principle of wire resonance. The accuracy of theresonance frequency measured is 0.1 Hz depending on the AC generator.
This paper describes a 2m threshold gas cerenkov counter for identifing π,K,Pparticles with momenta of 5 to 10 GeV/c. Velocity resolution of 3.5×10-5 has beenachieved. Detection efficieney on plateau is more than 99.99%. The rejection factorfor particle with energy below threshold is about 1.6×10-5.
The energy spectra of cosmic ray hadrons is studied by use of mountain emulsionchambers installed on Mt. Kambala 5500 m above sea level. The power index. of theenergy spectra is 1.95±0.18 in the energy region from 3 to 50 TeV The verticalflux of hadrons with Ehγ≥3 TeV is (145±14)/year.m2.sr, their attenuation lengthin air is (101±13)g/cm2, and mean interaction length in Pb is (187±51)g/cm2.
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