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1. B to π, B(s) to D(s)ℓν form factors from 2+1+1 flavor Lattice QCD

   Cassar, N; Chauhan, A; DeTar, C; El-Khadra, AX; Gámiz, E; Gottlieb, S; Jay, W; Kronfeld, A; Laiho, J; Lytle, A; et al (June 2026, PoS(LATTICE2025)252)

   Mathur, Nilmani; Padmanath, Madanagopalan; Raychowdhury, Indrakshi (Ed.)

   We present a lattice QCD calculation of the hadronic form factors for the semileptonic decays B→π and B(s)→D(s)ℓν, computed using the highly improved staggered quark action for both valence and sea quarks on the MILC collaboration’s 2+1+1-flavor ensembles with lattice spacings ranging from 0.09fm to 0.03fm, many with physical pion masses. On our finest ensembles, we compute the form factors directly at the physical b-quark mass. We discuss the computational setup and analysis strategies for two- and three-point correlation functions. For B(s)→D(s), we present preliminary results of chiral-continuum fits for the scalar and vector form factors. The goal of this project is a percent-level determination of the scalar and vector form factors to enable high-precision determinations of |Vub| and|Vcb|. This work fits into a broader program of lattice-QCD studies of weak B-meson decays by the MILC and Fermilab Lattice collaborations. 

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2. B- and D-meson semileptonic decays with highly improved staggered quarks

   https://doi.org/10.22323/1.396.0109  

   Jay, William; Lytle, Andrew; DeTar, Carleton; El-Khadra, Aida X; Gamiz, Elvira; Gelzer, Zechariah; Gottlieb, Steven; Kronfeld, Andreas; Simone, Jim; Vaquero, Alejandro (May 2022, The 38th International Symposium on Lattice Field Theory (LATTICE2021))

   We present results for B(s)- and D(s)-meson semileptonic decays from ongoing calculations by the Fermilab Lattice and MILC Collaborations. Our calculation employs the highly improved stag- gered quark (HISQ) action for both sea and valence quarks and includes several ensembles with physical-mass up, down, strange, and charm quarks and lattice spacings ranging from a ≈ 0.15 fm down to 0.06 fm. At most lattice spacings, an ensemble with physical-mass light quarks is included. The use of the highly improved action, combined with the MILC Collaboration’s gauge ensembles with lattice spacings down to a ≈ 0.042 fm, allows heavy valence quarks to be treated with the same discretization as the light and strange quarks. This unified treatment of the valence quarks allows (in some cases) for absolutely normalized currents, bypassing the need for perturbative matching, which has been a leading source of uncertainty in previous calculations of B-meson decay form factors by our collaboration. All preliminary form-factor results are blinded. 

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3. Semileptonic form factors for $$B\rightarrow D^*\ell \nu $$ at nonzero recoil from $$2+1$$-flavor lattice QCD: Fermilab Lattice and MILC Collaborations

   https://doi.org/10.1140/epjc/s10052-022-10984-9  

   Bazavov, A.; DeTar, C. E.; Du, D.; El-Khadra, A. X.; Gámiz, E.; Gelzer, Z.; Gottlieb, S.; Heller, U. M.; Kronfeld, A. S.; Laiho, J.; et al (December 2022, The European Physical Journal C)

   Abstract We present the first unquenched lattice-QCD calculation of the form factors for the decay $$B\rightarrow D^*\ell \nu $$ B → D ∗ ℓ ν at nonzero recoil. Our analysis includes 15 MILC ensembles with $$N_f=2+1$$ N f = 2 + 1 flavors of asqtad sea quarks, with a strange quark mass close to its physical mass. The lattice spacings range from $$a\approx 0.15$$ a ≈ 0.15 fm down to 0.045 fm, while the ratio between the light- and the strange-quark masses ranges from 0.05 to 0.4. The valence b and c quarks are treated using the Wilson-clover action with the Fermilab interpretation, whereas the light sector employs asqtad staggered fermions. We extrapolate our results to the physical point in the continuum limit using rooted staggered heavy-light meson chiral perturbation theory. Then we apply a model-independent parametrization to extend the form factors to the full kinematic range. With this parametrization we perform a joint lattice-QCD/experiment fit using several experimental datasets to determine the CKM matrix element $$|V_{cb}|$$ | V cb | . We obtain $$\left| V_{cb}\right| = (38.40 \pm 0.68_{\text {th}} \pm 0.34_{\text {exp}} \pm 0.18_{\text {EM}})\times 10^{-3}$$ V cb = ( 38.40 ± 0 . 68 th ± 0 . 34 exp ± 0 . 18 EM ) × 10 - 3 . The first error is theoretical, the second comes from experiment and the last one includes electromagnetic and electroweak uncertainties, with an overall $$\chi ^2\text {/dof} = 126/84$$ χ 2 /dof = 126 / 84 , which illustrates the tensions between the experimental data sets, and between theory and experiment. This result is in agreement with previous exclusive determinations, but the tension with the inclusive determination remains. Finally, we integrate the differential decay rate obtained solely from lattice data to predict $$R(D^*) = 0.265 \pm 0.013$$ R ( D ∗ ) = 0.265 ± 0.013 , which confirms the current tension between theory and experiment. 

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4. B- and D-meson leptonic decay constants and quark masses from four-flavor lattice QCD

   TUMQCD and Fermilab Lattice and MILC Collaborations: Bazavov, A.; Bernard, C; Brambilla, N.; Brown, N.; DeTar, C.; El Khadra, A.X.; Gámiz, E.; Gottlieb, S.; Heller, U.M.; Komijani, J.; et al (January 2019, 13th Conference on the Intersections of Particle and Nuclear Physics)

   We describe a recent lattice-QCD calculation of the leptonic decay con- stants of heavy-light pseudoscalar mesons containing charm and bottom quarks and of the masses of the up, down, strange, charm, and bottom quarks. Results for these quantities are of the highest precision to date. Calculations use 24 isospin-symmetric ensembles of gauge-field configura- tions with six different lattice spacings as small as approximately 0.03 fm and several values of the light quark masses down to physical values of the average up- and down-sea-quark masses. We use the highly-improved staggered quark (HISQ) formulation for valence and sea quarks, includ- ing the bottom quark. The analysis employs heavy-quark effective theory (HQET). A novel HQET method is used in the determination of the quark masses. 

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5. High-precision scale setting with the $\mathrm{\Omega }$ -baryon mass and gradient flow

   https://doi.org/10.1103/t18c-bpqy  

   Bazavov, Alexei; Bernard, Claude W; Clarke, David A; DeTar, Carleton; El-Khadra, Aida X; Gámiz, Elvira; Gottlieb, Steven; Grebe, Anthony V; Heller, Urs M; Hostetler, Leon; et al (March 2026, Physical Review D)

   The gradient-flow scale $w_0$ in lattice QCD is determined using the mass of the ${\mathrm{\Omega }}^{-}$ baryon to set the physical scale. Nine ensembles using the highly improved staggered quark (HISQ) action with lattice spacings of 0.15 fm down to 0.04 fm are used, seven of which have nearly physical light-quark masses. Electromagnetic corrections to the ${\mathrm{\Omega }}^{-}$ mass are defined in order to compute a pure-QCD $\mathrm{\Omega }$ mass. The final result is $w_0=0.17187\left(68\right)\mathrm{fm}$ , corresponding to a relative uncertainty of 0.40% and a central value in good agreement with previous calculations in the literature. 

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