1984 Vol. 8, No. 5
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The most accurate tau lifetime measurement in e+e－ experiments by now is reported by MARK Ⅱ with the value (3.20±0.41±0.35)×10－13 sec. wherein the second and the third terms are statistical and systematic errors respectively. By using TEC (Time Expansion Chamber) type vertex chamber with position resolution 40μ in r-φ plane at similar experimental condition (∫Ldt=40pb－1), MONTE-CARLO calculation shows: at center of mass energy √s =40GeV the statistical error of tau lifetime can be decreased to 0.13×10－13 sec. and the systematic error is in a comparable value.
We Construct a pion cloud MIT-bag model with chiral symmetry. The pion cloud outside the bag is a classical spherica field. The calculated hadron mass spectra are comparable with the experimental data. The decay width of Δ++(1236) calculated in this model is ΓΔ=115.8 MeV, which is very close to the experimental value. We also calculate the phase shift of P33 resonance. The resultin curve fits the experimental data exceedly well.
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－)+vμ are calculated with accuracy up to order O(α). The results are wΞ0→(Σ+μ－)+vμ1.12(1/sec) and R=[wΞ0→(Σ+μ－)+vμ]/[wΞ0→(Σ+μ－)+vμ]4.7×10-7. Similarly, the process Λ→(pμ－)+vμ is also discussed.
In the framework of the perturbative QCD, the two-fold differential cross section d2σ/dxTdxL of the reaction γ+p→2γ+X and its two backgrounds (γ+p→γ++X, γ+p→γ++X) are calculated in c.m.s.. The results show that, in a large range of (xT, xL), the calculated reaction cross section can be measured in current laboratory condition. And due to the properties of this reaction, i.e., large pT photoproduction and direct photon pair emission, all of the backgrounds can be greatly suppressed.
Using the fact that the proton contains the Charm State │uudcc〉 and combining its effects with the result of the usual calculations of A.J. Buras et.al., a better agreement of the theoretical value of the ratio R=σL/σT in e-p deep inelastic scattering with the experimental data is obtained.
Using discrete symmetry S, a systematic analysis of all possible GUT models based on the low rank group SU(N)×S is presented. It is found that only SU(7)×S and SU(8)×S are the satisfactory gauge groups of flavour grand unification. In addition, SU(7)×S and SU(8)×S models are discussed in detail. All these models can accommodate. four generations of ordinary fermions and preserve the asympotic freedom of SUc(3).
The multiple angular-correlation function for the sequential decays J/ψ→γ+G(3－+), G(3－+)→M1M2, where G is a Jpc=3－+ state and M1 and M2 are spinless mesons, is deduced. A 3－+ glueball state is discussed and the ratios of the helicity amplitudes of J/ψ→γ+G(3－+) are calculated. One ratio is independent of the glueball's mass and very small.
Under the Glauber approximation, the problem about the theoretical description of the excitation of the 9.5MeV level of 13C in π-13C inelastic scattering is discussed. We assume that the transition to the 9.5MeV level is semi-coherent one step process. The weak coupling nucleus model is used for the initial and final nucleus structure. Based on the assumption j=7/2+ and the approximation Γ(v)1/2Γ(s), the differential cross section of the inelastic 13C (π±, π′±) 13C*(9.5MeV) at Tlabπ=180MeV is calculated and compared with the existed data. The agreement is not quite satisfactory.
The design of the BPL 750keV beam transport system and the study of beam space charge effect in this system are described. This system has been constructed and operated in December 1982. The beam-transfer efficiency of the quadrupole system reached 66.7%. The first buncher operated in 1983, and the beam bunching efficiency is about 60%.
The difficulty of the classical dynamics in studing the mechanism of angular momentum transfer is discussed. According to the nuclear rotational concept formed in the study of the nuclear structure for a long time, we point out that it is convenient to divide the total angular momentum I transfered to the target and the projectile into two components-the nuclear collective angular momentum IR and the rotational alignment angular momentum Ij.
The solutions for the problem of 3 particles moving in a single-j shell are given from the shell model and the generator coordiuate method (GCM) respectively. After taking all possible contractions of fermions as well as bosons, GCM can produce the same exact solution as the shell model. So it is quite reasonable to expect that GCM is an effective theory in treating coupling between boson and fermion degrees of freedom in nuclei microscopically.
In this paper, the generate coordinator method (GCM) is applied to study the effect of multipole vibration on M1 transition of 1+ states in 208Pb. The calculation shows that coupling between 3－ collective state and (1p1h) gives much more effect than the coupling effect of 2+ state with (1p1h).
In this paper it is assumed that the quark-quark two-particle interaction is the coulomb-like plus exponential type confinement potential. The excited nucleonic and Δ's spectrum below 2 GeV has been stutied unifiedly by the potential. The calculated position of the resonances and the predicted mixing angles are in good agreement with the experiments. It is shown that the potential can describe successfully the properties of the low-lying non-strange baryon states.
The angular distributions of the elastic scattering for reaction 12C+28Si have been measured at the energies 69.5MeV, 66MeV, 59MeV, 56MeV using the large area position sensitive ionization chamber. The experimental data are fitted by use of the optical model. The probable reasons of the enhancement and oscillation of the elastic scattering angular distribution are discussed.
In terms of a systematic analysis of the relation between neutron number and Fermi surface (N~λn), the potential energy surface calculation and the shell corrections, it is found that the region appearing shape coexistence in Kr isotopes is located in a N-window N=38~42.
The relation between the masses of W± and Z0 in a composite model is disscused phenomenologycally. It is shown that any deviation of experimental data from the predicted value of W-S model will be in favour of the composite model.
By using present experimental data, the calculation results show that is W' (the radial excited state of W) exists, then its mass will be greater than (2—5)mw.
We show that the near correlation in rapidity is consistent with the requirements of QCD, and completely determines the combination rule of quarks. We give the formulae for calculating yields of mesons, baryons and antibaryons, which are produced by a stochastic accumulation of quarks with similar rapidities. Using it to e+e－ annihilation, the observation of recently unexpected copious production of baryons is explained naturally.
In this paper the reflection effects which appeared in RF system of BPL on the phase measurement and phase control are described. Some mathematical expressions about the effects are obtained. A concret method reducing the reflection effects is presented.
The variational method in Lagrangian formalism has been applied to investigate the SU(3) Wilson model in lattice gauge theory. No phase transition point has been found. The result is in agreement with that obtained by Monte Carlo simulations.
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