应用具有手征流关联函数的光锥求和规则计算B(B_c)→Dl■过程的形状因子(英文)

Form Factors for B(B_c)→DI■ in Light-Cone Sum Rules with Chiral Current Correlator

在QCD光锥求和规则(LCSR)框架内应用具有手征流关联函数计算B(B_c)→Dl■衰变过程的弱形状因子.所获得的形状因子的表达式仅依赖于D介子的主导级分布振幅(DA).应用了三类D介子的分布振幅计算了形状因子F_(B→D)(0)和F_(B_c→D)(0).在速度迁移1.14<y<1.59的区域内使在光锥x^2=0附近算符乘积展开(OPE)得以有效的情况下所计算的形状因子行为在误差范围内与B→Dl■过程实验数据相一致.在大反冲区域1.35<y<1.59获得的形状因子F_(B→D)(0)是与微扰QCD(pQCD)结果相一致的.所以本文的计算在联接格点QCD,重夸克对称性和pQCD之间起桥梁作用,有助于进一步对B→Dl■跃迁过程的理解.计算使用了在端点具有指数压低的分布振幅行为,对F_(B_c→D)(0)的预言与其他方法获得的结果是可比的,有利于具有库仑修正的三点求和规则(3PSR)方法所得的结果.

In this paper we calculate the weak form factors of the decays B（Bc） → Dlv^- by using the chiral current correlator within the framework of the QCD light-cone sum rules （LCSR）. The expressions of the form factors only depend on the leading twist distribution amplitude （DA） of the D meson. Three models of the D- meson distribution amplitude are employed and the calculated form factors,FB→D （0） and FBC→D （0） are given. In the velocity transfer region 1.14 〈 y 〈 1.59, which renders the Operator Product Expansion （OPE） near light-cone x^2 = 0 to go effectively, the yielding behavior of form factor is in agreement with that extracted from the data on B → Dlv^-, within the error. In the large recoil region 1.35 〈 y 〈 1.59, the form factor FB→D（0） is observed consistent with that of perturbative QCD （pQCD）. The presented calculation can play a bridge role connecting those from the lattice QCD, heavy quark symmetry and pQCD to have an all-around understanding of B→ Dlv^- transitions. Our prediction for FB→D（0）, by using the D-meson distribution amplitude with the exponential suppression at the end points, is compatible with other approaches, and favors the three-points sum rules （3PSR） approach with the Coulumb corrections.