Form factors of B,B_s→η^(′) and D,D_s→η^(′) transitions from QCD light-cone sum rules

In the framework of the QCD light-cone sum rules (LCSRs) we present the analysis of all B,Bs→η(′) and D,Ds→η(′) form factors (f+,f0 and fT) by including mη(′)2 corrections in the leading (up to the twist-four) and next-to-leading order (up to the twist-three) in QCD, and two-gluon contributions to the form factors at the leading twist. The SU(3)-flavour breaking corrections and the axial anomaly contributions to the distribution amplitudes are also consistently taken into account. The complete results for the f0 and fT form factors of B,Bs→η(′) and D,Ds→η(′) relevant for processes like B→η(′)τντ or Bs→η(′)l+l− are given for the first time, as well as the two-gluon contribution to the tensor form factors. The values obtained for the f+ form factors are as follows: fBη+(0)=0.168−0.047+0.042, |fBsη+(0)|=0.212−0.013+0.015, fBη′+(0)=0.130−0.032+0.036, fBsη′+(0)=0.252−0.020+0.023 and fDη+(0)=0.429−0.141+0.165, |fDsη+(0)|=0.495−0.029+0.030, fDη′+(0)=0.292−0.104+0.113, fDsη′+(0)=0.558−0.045+0.047. Also phenomenological predictions for semileptonic B,Bs→η(′) and D,Ds→η(′) decay modes are given.