2000 Vol. 24, No. 12
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In this paper, the cross-sections of single W boson production e+e－→e－νe W+ and e+e－→e+νe W－ were measured based on the data samples collected by the L3 detector in 1996 and 1997. The limits on the anomalous couplings Of WWγ triple gauge boson are derived at 95% CL: －0.65<△κγ <0.82 and －1.37<λγ <0.92. The results are consistent with the Standard Model predictions and no anomalous couplings are found.
The Geographical location of Yangbajing is suitable for the direct detection of the solar flare neutron events. The Yangbajing neutron telescope (NT) and Neutron Monitor (NM) were established in 1998 October to provide the observation of solar neutrons during the 23rd solar cycle. An unusual large enhancement of the NT and NM count rates over background was observed from 05: 38 UT to 05: 40 UT at Yangbajing on 1998 November 28.
We calculate the contributions of extended technicolor (ETC) interaction to CP violation asymmetry parameter δ in top quark pair Production, δ = σ[e-e→t(-)-t(-)]-σ[e-e→t(+)-t(+)]/σ(e-e→t-t), in topcolor-assisted multiscale technicolor (TOPCMTC) model. Using the new LEP value of Rb, we give the numerical results. Our results show that ETC interactions can produce significantly effects on CP violation for a certain range of the parameters in TOPCMTC model. For 5 00 GeV<1/2s< 15 00 GeV, the value of parameter δ is in the range of 8. 65×10－3 ≤δ≤1. 09×10－2. We expect that this effect may be testable in the future NLC experiments.
Using the improved lattice Hamiltonian and the truncated eigenvalue equation method,we compute the glueball mass of (2+1) dimensional SU(2) gauge field theory. The numerical result displays a very good scaling behavior in the wide coupling region (1.0≤ 1/g2≤8.0).
The analytical helicity amplitudes for Z→3γ and it's related processes via w-loop and charged scalar loop are presented. There are some differences between our results and those in Glover paper for Z→3γ via w-loop and fermion loop. Although these differences do not contradict the result of total decay width for Z→3γ, but the different helicity amplitudes have measurable physical meanings. We discuss the definition of polarization vector and point out the error of Glover paper.
For the emergence of Berry geometric phase, we analyze the relevant physical background condition of the weak transitions among quantum energy-levels. We elaborate a further discussion on the internal relationship between the strict obtainment of Berry geometric phase and the weak transitions. Our study shows that the strict obtainment of Berry geometric phase is the natural result of the adiabatic limit effect of weak transitions among quantum energy-levels. These transitions occur inevitably during the evolution process of quantum system.
The eigenstates of the Kth powers (K≥3) of the annihilation operator of the Q- deformed non-harmonic oscillator are constructed, and their completeness and higher-order Squeezing properties are investigated. The results show that they form a complete Hilbert space, and the Mth order [M=(n+1/2)K; n = 0,1,2,…] Squeezing effects exist in all of the eigenstates when K is even.
High-spin states in 178Ir have been produced and studied via the 152Sm(30p,5nγ)178Ir reaction. In-beam γ rays were measured including the excitation functions at 150,155,160,165 and 170 MeV beam energies,K X-γ and γ-γ coincidences at 160 MeV. According to the band structure characteristics and the deduced intra-band B (M1)/B (E2) ratios, two rotational bands are identified for the first time and assigned to be associated with the πh9/2νi13/2 and the πh11/2νi13/2 quasiparticle configurations respectively. Low-spin signature inversion in bob bands has been confirmed hased on the observation of signature crossing at Ic=21h for the πh9/2νi13/2, semidecoupled band and at Ic=16 h for the πh11/2νi13/2 strongly coupled band, respectively. Systematics of the signature inversion has been discussed for the semidecoupled bands in the A=160-180 mass region and some regularities are proposed concerning the crossing spins with variation of mass. The signature splitting in the πh11/2νi13/2 band of 178Ir is smaller than that in the similar band of 176Re; this trend is opposite to the predictions based on the projected shell model.
The statistical emission of the 35MeV/u 40Ar+197Au was studied. Several silicon △E1+ silicon △E2+CsI(Tl) telescopes with good particle identification and lower energy thresholds were used to collect the experimental data. For the backward angle emission events, the slope nuclear temperature parameters and the isotope nuclear temperature parameters, which were extracted from the slope of energy spectra and double isotope yield ratios of the reaction products respectively, were nearly the same. The slope temperatures were slightly higher than the isotope temperatures. The reliability of the method to extract nuclear temperature has been discussed. For the backward angle events statistical emission is the dominant process, i. e. the particles emitted into backward angles mainly come from the equilibrium decay.
This paper researches resonance phenomenon in the fast neutron radiative capture reaction. 12C(n, γ0) cross sections are calcaulated in the neutron energy range of 5-25 MeV and angular distribution is calcaulated at neutron energy 9MeV by DSD model. Reaction mechanism contains five terms: the compound nucleus capture, direct capture and semidirect capture, radiative capture in compound elastic and inelastic channels. The calculations display the pygmy resonance peak at excitation energy Ex=13MeV and the giant resonance peak at excitation energy Ex=21MeV. The calculations agree with exepermental results.
The influence of the decoupling term in K=1/2 band on the extraction of the nuclear moments of inertia is investigated. The peculiar characters in the variation of the nuclear moments of inertia with spins are itemized for the K=1/2 band. On this basis three recently observed superdeformed bands in 193T1 are discussed. An optimum explanation of the configuration structures is pro-posed to these bands. No sufficient evidence exists to conclude that all of them are of K=1/2.
The derivative expansion method is used to solve the kinetic equations of quark-gluon plasma. In the process of solution, we find that the self-interaction term of the mean field equation plays an important role to the nonlinear eigenfrequency shift of the non-Abelian excitations in quarkgluon plasma. To the third order of derivative expansion, we get the general analytical expression of nonlinear frequency shift including the self-interaction in the leading order of coupling constant and give out the value of eigenfrequency shift for the pure gluon plasma to the important k=0 modes.
The tensor coupling of the ω meson to nucleon in modified derivative scalar coupling (MDSC) model for finite nuclei was investigated. In addition to the spin-orbit splittings improved by the tensor coupling, our results show that the tensor force (or the effect of the tensor coupling) shows attractive in the interior of nuclei, and then becomes repulsive in the surface region. As a result, the single-particle states are more bound for very deeplying orbits, and less bound for those very near the Fermi energies.
An algorithm based on VCJULI to calibrate the BES Ⅱ vertex chamber is described. The calibration includes the determination of global T0, the subtraction of t0 shift for each wire, the corrections of wire position itself and the position of the vertex chamber relative to the main drift chamber, the establishment of drift time to drift distance relation, etc. The main performance of the BES Ⅱ vertex chamber is given accordingly: space resolution is better than 100μm.
The article presents the study and new development at SFC, the HIRFL injector cyclotron. It includes the new central region, the new buncher system and the new axial injection line. It introduces the half-frequency bunching method to increase the longitudinal matching efficiency between the injector and the main cyclotron and the special treatment for the space charge effect by using two injection parameters. The constant orbit acceleration with small variation is introduced to solve the contradiction of the lower RF voltage and less turn number. Two on-line ECR ion sources, high charge state resolving power and other improvements on the injection line have been included.
The temperature of electron beam is an important parameter in electron cooling device. Transverse temperature will be reduced When an electron beam passes through a negative gradient magnetic field. Some theoretical approaches on adiabatic expansion are presented here. Adiabatic expansion of the electron beam moving in different magnetic fields with different energy and current was investigated by computer simulation. The results show that the transverse temperature of the electron beam is reduced by a factor equal to the ratio between the initial and final magnetic field strengths, provided that the field change is adiabatic with respect to the cyclotron motion of the electrons.
Synchrotron radiation X-ray grazing incident diffraction (GID) method was developed based on the five-circle diffractometer in the Diffuse Scattering Station at Beijing Synchrotron Radiation Facility. The lateral strain induced by the Ge/Si quantum dotswas measured successfully, which showed the capability of the GID method in measuring weak signals from surface structures. The results showed that the formation of Ge/Si quantum dots caused both the lateral expansion-strain and contraction-strain in the surface layer of Si(001) substrate.
β-delayed fission for 230Ac was searched. 230Ra was produced via multinucleon transfer reaction by 60MeV/u 18O ion irradiation of 232Th target. Thin 230Ra→β-230Ac sources of 108 atoms were acquired through radiochemical separations. The mica track detectors were used to record the fission events. The β-delayed fission nucleus 230Ac was identified via the observed two fission events and the measured γ-ray spectra. Its β-delayed fission probability was obtained to be (1.19±0.85)×10－8.
The collective motion of a pure octupole deformed system is treated as the vibrations in body-fixed frame and rotation of this system about the axes of lab-system,as well as the coupling between vibrations and rotation. The quantized operator of kinetic energy is derived and the collective spectra built on some special equilibrium shape are discussed.
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