首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
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.  相似文献   

2.
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.  相似文献   

3.
In the framework of the MIT bag model and under Born-Oppenheimer approximation, the 1--QQqq states and their mixing with QQ states are discussed, where Q=c, b; q=u, d, and both QQ and qq are colour singlets. The mixing is introduced through a coupling, constant. An approximate scaling law for hadronic transitions (QQ)′→(QQ)ππ could be obtained and the ratio of Γ(ψ′→4ππ) to Γ(Υ′→Υππ) could be compatible with the data if the coupling constant is flavour-independent. The mixing is dominated by QQqq states in which qq is a P-wave 0++ state and therefore the observed isotropic angular distribution of the pion in ψ′→ψππ and γ′→γππ can be well explained.  相似文献   

4.
Based on the most important "hard" production mechanism,the production rate of Bc(or Bc) meson being accompanied with one c(or c) and one b(or b) heavy quark jets through Z0 decay is computed in this paper.It is pointed out that at LEP up to next run,quite a lot of events with one Bc or Bc meson may be obtained,so that it becomes accessible to study the properties of Bc and Bc mesons throngh Z0 decay experimentally.  相似文献   

5.
Based on 58 million J/ψ events collected by the BESⅡ detector at the BEPC, J/ψ→ΛΛ π+π- is observed for the first time. The branching fraction is measured to be Br(J/ψ→ΛΛ π+π-)=(4.30±0.13±0.99)×10-3, excluding the decays to intermediate states, namely J/ψ→Ξ-Ξ+, J/ψ→Σ(1385)-Σ(1385)+, and J/ψ→Σ(1385)+Σ(1385)-. The branching fractions for these intermediate resonance channels are measured to be:Br(J/ψ→Ξ-Ξ+)=(0.90±0.03±0.18)×10-3, Br(J/ψ→Σ(1385)-Σ(1385)+)=(1.23±0.07±0.30)×10-3,and Br(J/ψ→Σ(1385)+Σ(1385)-)=(1.50±0.08±0.38)×10-3, respectively. The angular distribution is of the form dN/d(cosθ)α(1+αcos2θ) with α=(0.35±0.29±0.06) for J/ψ→Ξ-Ξ+, α=(-0.54±0.22±0.10) for J/ψ→Σ(1385)-Σ(1385)+, and α=(-0.35±0.29±0.06) for J/ψ→Σ(1385)+Σ(1385)-.  相似文献   

6.
The beam envelops for non-periodic alternating gradient focusing system is analysed. The accurate analytic expressions of the beam envelop function β is obtained by solving the following non-linear differential equation:(√β)н+Q(Z)√β-1/(√β)3=0,
The conditions of existing the maximum and the minimum of beam envelop are discussed. And we have derived the accurate formulae with which one can calculate the maximum and the minimum values of envelop and their position. The method developed in this paper is different from the convintional matrix computational method. Both methods can be checked by each other.  相似文献   

7.
In the two-quark model supposition for K0*(1430), which can be viewed as either the first excited state (Scenario Ⅰ) or the lowest lying state (Scenario Ⅱ), the branching ratios and the direct CP-violating asymmetries for decays Bs0→K0*0(1430)η(') are studied by employing the perturbative QCD factorization approach. We find the following results: (a) The CP averaged branching ratios of Bs0→K0*0(1430)η and Bs0→K0*0(1430)η' are small and both in the order of 10-7. If one views K0*(1430) as the lowest lying state, B (Bs0→K0*0(1430)η)≈3.9×10-7 and B (Bs0→K0*0(1430)η')≈7.8×10-7. (b) While the direct CP-violating asymmetries of these two decays are not small: if we still take the parameters of K0*(1430) in scenario Ⅱ, ACPdir (Bs0→K0*0(1430)η)≈56.2% and ACPdir (Bs0→K0*0(1430)η')≈2.4%. (c) The annihilation contributions will play an important role in accounting for future data, because both the branching ratios and the direct CP asymmetries of these two decays are sensitive to the annihilation type contributions.  相似文献   

8.
In this paper I summarize some results obtained from analyses of hadronic final state events. The analyzed data sample comes from Mark-J collaboration and covers an energy range from √S=12GeV to √S =46.78GeV. The integrated luminosity is 128.06Pb-1. We can search for production of open top quarks and toponium by measuring the total hadronic crossection R =3.85±0.02±0.12 was measured in the above mentioned energy range. It is consistent with R≈3.9 as expected from QCD for five different quark flavors. We search for the narrow bound states of the toponium from 39.79GeV to 46.78GeV. The most prominent resonance signal is at a c.m. energy √S=45.12±0.04GeV and results in an upper limit of Bh.Γee≤3.00keV(95% C.L.).  相似文献   

9.
A simple method is proposed to obtain the classical monopole and dyon solutions in the case of SU(4) symmetry, which can be systematically generalized to the general case of SU(N). The solutions obtained in the SU(4) case correspond to magnetic charges of ±1/g,±3/(2g),±1/(√2g).  相似文献   

10.
The decay ψ(2S)→Ω-Ω+ is analyzed using 14×106 ψ(2S) events recorded by the Beijing Spectrometer Ⅱ (BESⅡ) at the Beijing Electron Positron Collider (BEPC). Based upon events with no missing charged tracks and a satisfactory four-constraint kinematic t, we determine the upper limit for the branching fraction of ψ(2S)→Ω-Ω+ to be 1.5×104 at a 90% confidence level. By including events with one missing charged track, we are able to report the first evidence of an Ω+ signal with a statistical signi cance of 3.1|σ. The branching fraction of ψ(2S)Ω+ is determined to be (4.80±1.56(stat)±1.30(sys))105.  相似文献   

11.
A general phenomenological analysis of vp、vp、ve、and ve elastic scattering is presented and the polarization effects of the targets and final recoil particles are also considered. The space-time structure of the weak neutral currents is examined systematically. Under some paticular conditions, the criteria for the existence of various couplings are given.  相似文献   

12.
The structure properties of Li isotopes are investigated in the framework of large-basis shell model.0hω calculation can reproduce the structure of 6,7Li, but for some states of 8,9 Li far from β-stability line the effect of(0+2)hω excitation should be taken into account for reproducing the experiment at data.For drip line nuclei,enlarging model space or changing the interaction can not reproduce the exotic properties of nucleus 11Li.The exotic properties of some states of nuclei 6—8Li are also briefly discussed.  相似文献   

13.
We continue the investigation of the equation and its solutions for the bound states of mesons discussed previously, emphasizing on large values of v, a parameter characterizing the shape of the potential. The results show that the dependence of the eigenvalues λ and some related physical quantities upon the potential parameters v and E is approximately the same as in our previous work. But the average radii of the bound mesons cease increasing as v increases. For each value of v, there exists a maximum average radius√<R2>max, and all these √<R2>max are approximately equal to 12.6 M-1 (M being the mass of the straton), which is much smaller than the experimental value of the radius of the π meson. However, if we assume, in addition to the attractive potential, there exists, for the straton-anti-straton superstrong interactions, also a repulsive potential, and, in particular, if we introduce a differencetype potential VDr) corresponding to the potential Vvr) in our previous work, the calculated radii of the bound mesons do approach the experimental value.  相似文献   

14.
In this article, we calculate the form-factors of the transitions B → a1(1260), b1(1235) in the leading-order approximation using the light-cone QCD sum rules. In calculations, we choose the chiral current to interpolate the B-meson, which has the outstanding advantage that the twist-3 light-cone distribution amplitudes of the axial-vector mesons makes no contributions, and the resulting sum rules for the form-factors suffer from far fewer uncertainties. Then we study the semi-leptonic decays B → a1(1260) lvl, b1(1235) lvl (l=e,μ,τ), and make predictions for the differential decay widths and decay widths, which can be compared with the experimental data in the coming future.  相似文献   

15.
In this note we propose that the electromagnetic self energy of lepton may beconnected with quantum number n by( (δm)/m)=(1/(2π))n-b ,in which b is a constant.Wefnrther propose that the cut-off value of momentum M is connected with gravitationalconstant κ and fine structure constant α by M=(1/√καe-1-b.So we obtainthe mass formula of charged leptons M=(1/√κα exp{-3/4-b-(1/3α)n-b}.By using the masses of e- and μ- and the value of a as in put,we get the calculatedvalues of κ=(6.67231±0.00026)×10-8cm3g-1sec-2and mr=(1782.306±0.078)MeVwhich agree very well with experimental values κ=(6.6720±0.0041)×10-8cm3g-1sec-2 and mτ=(1782-4+3)MeV respectively.The mass of the fourth charged leptonpredicted by the formula should be m=(11725.47±0.51)MeV,which can be checkedby experiments in the near future.We also discuss briefly the proposed formula andthe obtained results.  相似文献   

16.
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 RLT in e-p deep inelastic scattering with the experimental data is obtained.  相似文献   

17.
In this paper, the matrix elements of the nucleon-meson vertices due to one gluon exchange transition potential Vq→qqq are calculated by using the generator coordinate method. We obtain that the interaction forms of the vertices are the same as the nonrelativistic forms coming from the interactions of the nucleon field and the meson field; and the coupling constants are roughly consistent with the experimental data.  相似文献   

18.
We discuss the suppression of the decay of heavy lepton τ into πvτ,by assuming that τ and/or vτ carry spin 3/2. For the case of spin 3/2 T and spin 1/2 vτ, using the weak current ψμ(τ)(a+bγ5)Ψ(vτ)we find that the πvτ decay channel relative to the vτvll-channel is suppressed 12/5 times, while other decay channels are not changed appreciably. △R=σ(e+e-τ+τ-)/σ(e+e-μ+μ-) is also discussed.  相似文献   

19.
In the framework of the Color Glass Condensate, the pseudo-rapidity distributions of charged hadrons in pp and pA collisions at the LHC are studied with the UGD function from the GBW model. With a χ2 analysis of the CMS data in pp collisions at √s=0.9, 2.36, 7 TeV, the normalization factor is obtained and the theoretical results are in good agreement with the experimental data. Then, considering the influence of nucleon hard partons transverse distribution on the number of participants in pA collisions by using a Glauber Monte Carlo method, we also give the predictive results for the multiplicity distributions in pPb collisions at √s=4.4 TeV.  相似文献   

20.
Inclusive distributions of longitudinal momentum and energy ((S/β) (dσ/dxp)and (S/β) (dσ/dxE)) in a quark jat for e+ e- collidiny is calculated (√S~7GeV), fased onrandomly producing wee quarks and phase-space eonsideration. Excellent fits areobtained. In addition, a two-particle correlation dσ/(dxIEdx2E) is also given, which ex-pects experimental tests.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号