Subleading power factorization in B ¯ → X s ℓ + ℓ − $$ \overline{B}\to {X}_s{\ell}^{+}{\ell}^{-} $$

We analyze the factorization to subleading power in the flavor changing neutral current process $$ \overline{B}\to {X}_s{\ell}^{+}{\ell}^{-} $$ . In particular, we compute the so-called resolved contributions and explore the numerical impact on observables. In these contributions the virtual photon couples to light partons instead of connecting directly to the effective weak-interaction vertex. They represent an irreducible uncertainty in the inclusive $$ \overline{B}\to {X}_s{\ell}^{+}{\ell}^{-} $$ decay which cannot be removed by relaxing the experimentally necessary cuts in the hadronic mass spectrum.