The Bc → Bsπ decay is studied with the perturbative QCD approach. Three types of wave functions for Bs meson are considered. The transition form factor F0Bc → Bsπ （0） and the branching ratio IBr（Bc → Bsπ） are sensitive to the model of the Bs meson wave functions. With appropriate inputs, our estimate on 23r（Bc → Bsπ） is comparable with the recent LHCb measurement. A clear signal of Bc → Bsπ decay should be easily observed at the Large Hadron Collider.
The currently accepted value for the upper limit on the photon rest mass comes from a rough estimate based on the solar wind method.We reconsider this method and present a more detailed analysis of the electromagnetic fields in interplanetary space.The simple analytic expressions for the solar wind magnetic field,electric field and current are obtained with a finite photon mass.The upper limit on the photon mass is re-estimated as mγ<0.8×10^(-54) kg,which improves the current bound by up a factor of 2,and further confirms the reliability of the solar wind method.
Within the hidden local symmetry framework, the Dalitz decay η→Ve＋e-is studied with the vector meson dominance model. It is found that the partial width Γ（η→ωe＋e-）≈40 e V and branching ratio B（η→ωe＋e-）≈2×10^-4, and Γ（η→ρe＋e-）≈10Γ（η→ωe＋e-） and B（η→ρe＋e-）≈10B（η→ωe＋e-）. The maximum position of the dilepton distribution is m e＋e-≈1.33 Me V. These decays are measurable with the advent of high statistic ηexperiments.
Newton’s law of gravity is a theory of instantaneous action at a distance.However,Einstein’s general relativity states that the speed of gravity equals the speed of light,which is finite.Therefore,it is a worthy problem to discuss if Newton’s law of gravity needs modification,when studying and observing the gravitational tidal.In this paper,it is shown that the Newton’s law of gravity is fully applicable in the framework of general relativity.Based on the post-Newtonian approximation,we find that the observable effect for the speed of gravity is irrelevant to the velocity of a moving source,but it is dependent on its acceleration.In general,the effect of the speed of gravity is so weak that today’s any astronomical observations,including the sun tidal observations,can not confirm that the gravitational field travels at the speed of light.
