B-meson semileptonic form factors on (2+1+1)-flavor HISQ ensembles

We report updates to an ongoing lattice-QCD calculation of the form factors for the semileptonic decays B → π`ν, B<sub>s</sub> → K`ν, B → π`<sup>+</sup>`⁻, and B → K`<sup>+</sup>`⁻. The tree-level decays B₍s₎ → π(K)`ν enable precise determinations of the CKM matrix element |V<sub>ub</sub>|, while the flavor-changing neutral-current interactions B → π(K)`⁺`⁻ are sensitive to contributions from new physics. This work uses MILC's (2+1+1)-flavor HISQ ensembles at approximate lattice spacings between 0.057 and 0.15 fm, with physical sea-quark masses on four out of the seven ensembles. The valence sector is comprised of a clover b quark (in the Fermilab interpretation) and HISQ light and s quarks. We present preliminary results for the form factors f₀, f₊, and f_T, including studies of systematic errors.