Precise Study Of The Basic Properties Of Light Mesons Within QCD Sum Rules Approach

In this paper,we mainly use quantum chromodynamics(QCD)sum rules approach to calculate the basic properties of light mesons,including distribution amplitude,transition form factor,decay branching function,decay width and CabibboKobayashi-Maskawa(CKM)matrix element.Firstly,according to Shifman-VainshteinZakharov(SVZ)sum rule and the knowledge of background field theory,we study in detail the moments of the twist-2 distribution amplitudes of pseudoscalar meson ?^(')and axial vector meson a₁(1260).The non-perturbative condensates up to dimensionsix,and the perturbative part is corrected by QCD next leading order(NLO).Then the transition form factor corresponding to the semi-leptonic decay process is calculated according to the light cone sum rule.After extrapolating the transition form factor to the allowable physical regions within the series expansion,we can calculate the corresponding decay process's decay branch function,decay width or CKM matrix element.Due to the particularity of ?^(')meson quark component,there are two different component quarks,which are calculated respectively.Also calculated ?-?'mixing angle between.As the abnormal dimension of Gegenbauer moment increases with the increase of n,the contribution of higher order Gegenbauer moment is suppressed,resulting in pseudo-oscillation,which leads to inaccurate calculation results.In order to improve the calculation accuracy,we use the improved light-cone harmonic oscillator model(LCHO)to redetermine the ?_q^(')meson twist-2 distribution amplitude and a₁(1260)meson longitudinal twist-2 distribution amplitude.We calculate the moment of the distribution amplitude to 10-order,and use the least square method to fit the moment of the distribution amplitude to obtain the optimal solution of the parameters.The parameters are brought into the new model to obtain the specific twist-2 distribution amplitude.This paper three semi-leptonic decay processes are calculated,which are D_s+??_s^(')l+v_l,D?a₁(1260)l+?_l and B(D)+??_q^(')l+?_l,respectively.The numerical results of transition form factor,decay width and branching function are in good agreement with theoretical and experimental groups,which lays a theoretical foundation for the experiment.