Ds-meson leading-twist distribution amplitude within the QCD sum rules and its application to the Bs→Ds transition form factor

We make a detailed study of the Ds-meson leading-twist light-cone distribution amplitude ϕ2 ;Ds by using the QCD sum rules within the framework of the background field theory. To improve the precision, its moments ⟨ξn⟩2 ;Ds are calculated up to dimension-six condensates. At the scale μ =2 GeV , we obtain ⟨ξ1⟩2 ;Ds=-0.261-0.020+0.020 , ⟨ξ2⟩2 ;Ds=0.184-0.012+0.012 , ⟨ξ3⟩2 ;Ds=-0.111-0.012+0.007 , and ⟨ξ4⟩2 ;Ds=0.075-0.005+0.005 . Using those moments, the ϕ2 ;Ds is then constructed by using the light-cone harmonic oscillator model. As an application, we calculate the transition form factor f+Bs→Ds(q2) within the light-cone sum rules (LCSR) approach by using a right-handed chiral current, in which the terms involving ϕ2 ;Ds dominate the LCSR. It is noted that the extrapolated f+Bs→Ds(q2) agrees with the lattice QCD prediction. After extrapolating the transition form factor to the physically allowable q2 region, we calculate the branching ratio and the CKM matrix element, which give B (B¯s 0→Ds+ℓνℓ)=(2.03-0.49+0.35)×10-2 and |Vc b|=(40.00-4.08+4.93)×10-3 .