B → D1(2420) and B → D 1 ′ $$ {\mathrm{D}}_1^{\prime } $$ (2430) form factors from QCD light-cone sum rules

Abstract

Abstract We perform the first calculation of form factors in the semileptonic decays B → D 1(2420)ℓν ℓ and B → D 1 ′ $$ {D}_1^{\prime } $$ (2430)ℓν ℓ using QCD light-cone sum rules (LCSRs) with B-meson distribution amplitudes. In this calculation the c-quark mass is finite. Analytical expressions for two-particle contributions up to twist four are obtained. To disentangle the D 1 and D 1 ′ $$ {D}_1^{\prime } $$ contributions in the LCSRs, we suggest a novel approach that introduces a combination of two interpolating currents for these charmed mesons. To fix all the parameters in the LCSRs, we use the two-point QCD sum rules for the decay constants of D 1 and D 1 ′ $$ {D}_1^{\prime } $$ mesons augmented by a single experimental input, that is the B → D 1(2420)ℓν ℓ decay width. We provide numerical results for all B → D 1 and B → D 1 ′ $$ {D}_1^{\prime } $$ form factors. As a byproduct, we also obtain the D 1- and D 1 ′ $$ {D}_1^{\prime } $$ -meson decay constants and predict the lepton-flavour universality ratios R(D 1) and R( D 1 ′ $$ {D}_1^{\prime } $$ ).

Keywords

• Bottom Quarks
• Semi-Leptonic Decays
• Rare Decays