Bs → Klν decay from lattice QCD
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Lattice, F., Collaborations, M. I. L. C., Bazavov, A., Bernard, C., DeTar, C., Du, D., ... & Gottlieb, S. (2019). B s→ K ℓ ν decay from lattice QCD. Physical Review D, 100(3), 034501.
SponsorshipThis project was supported in part by the URA Visiting Scholar Award 12-S-15 (Y. L.); by the U.S. Department of Energy under Grants No. DE-FG02-91ER40628 (C. B.), No. DE-FC02-12ER41879 (C. D.), No. DE-FG02- 13ER42001 (A. X. K.), No. DE-SC0015655 (A. X. K., Z.G.), No. DE-SC0010120 (S. G.), No. DE-FG02- 91ER40661 (S. G.), No. DE-SC0010113 (Y. M.), No. DESC0010005 (E. T. N.), No. DE-FG02-13ER41976 (D. T.); by the U.S. National Science Foundation under Grants No. PHY14-14614 and No. PHY17-19626 (C. D.), and No. PHY14-17805 (J. L.); by the MINECO (Spain) under Grants No. FPA2013-47836-C-1-P and No. FPA2016- 78220-C3-3-P (E. G.); by the Junta de Andalucía (Spain) under Grant No. FQM-101 (E. G.); by the Fermilab Distinguished Scholars program (A. X. K.); by the German Excellence Initiative and the European Union Seventh Framework Program under Grant Agreement No. 291763 as well as the European Union’s Marie Curie COFUND program (A. S. K.).
We use lattice QCD to calculate the form factors f+(q2) and f0(q2) for the semileptonic decay Bs→Kℓν. Our calculation uses six MILC asqtad 2+1 flavor gauge-field ensembles with three lattice spacings. At the smallest and largest lattice spacing the light-quark sea mass is set to 1/10 the strange-quark mass. At the intermediate lattice spacing, we use four values for the light-quark sea mass ranging from 1/5 to 1/20 of the strange-quark mass. We use the asqtad improved staggered action for the light valence quarks, and the clover action with the Fermilab interpolation for the heavy valence bottom quark. We use SU(2) hard-kaon heavy-meson rooted staggered chiral perturbation theory to take the chiral-continuum limit. A functional z expansion is used to extend the form factors to the full kinematic range. We present predictions for the differential decay rate for both Bs→Kμν and Bs→Kτν. We also present results for the forward-backward asymmetry, the lepton polarization asymmetry, ratios of the scalar and vector form factors for the decays Bs→Kℓν and Bs→Dsℓν. Our results, together with future experimental measurements, can be used to determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element |Vub|.