Laplace与有限能量两种求和规则在奇异重子Σ中的应用

Application of Laplace Sum Rule and FESR for Σ Baryon

采用Laplace求和规则与有限能量求和规则研究了8重态奇异重子Σ的基态与激发态的质量与衰变宽度.所有被考虑的重子能态的谱函数均采用Breit-Wigner有限宽度的形式.两种方法即两种求和规则交替使用与仅采用有限能量求和规则(FESR)所得到的理论预言是一致的,且与实验数据符合.与谱函数的零宽度近似相比,结果有一定的改善.这不仅说明了谱函数有限宽度在实际计算中的作用,而且由此发展的两种应用求和规则的方法都可以用来自洽地计算强子的基态与激发态的性质.

The mass and the decay width of the ground state and the first two excited ones for the sigma baryon in the eight-fold multiplet are investigated using the Laplace sum rules as well as the finite-energy ones. The spectral functions of all considered baryon states are adopted to be of the Breit-Wigner form of finite widths. Two calculation procedures, namely the combined usage of the Laplace and finite-energy sum rules as well as merely taking use of the finite-energy sum rules, lead to the consistent results of the theoretical predictions which agree with the experimental data. In comparison with the results using a zerowidth approximation for the spectral functions, the theoretical values of both the masses and the decay widths are improved to some extent. It shows not only the effects of the finiteness of the decay widths of the hadron states in practice, but also that the two procedures designed in this paper for using QCD sum rules can be consistently used to calculate the characteristics of the ground state and the lower-lying excited states of hadrons.