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

Abstract

Abstract We perform the first calculation of form factors in the semileptonic decays B → D1(2420)ℓνℓ and B → $$ {D}_1^{\prime } $$ D 1 ′ (2430)ℓνℓ 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 D1 and $$ {D}_1^{\prime } $$ D 1 ′ 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 D1 and $$ {D}_1^{\prime } $$ D 1 ′ mesons augmented by a single experimental input, that is the B → D1(2420)ℓνℓ decay width. We provide numerical results for all B → D1 and B → $$ {D}_1^{\prime } $$ D 1 ′ form factors. As a byproduct, we also obtain the D1- and $$ {D}_1^{\prime } $$ D 1 ′ -meson decay constants and predict the lepton-flavour universality ratios R(D1) and R($$ {D}_1^{\prime } $$ D 1 ′ ).