Toward accurate form factors for B -to-light meson decay from lattice QCD

We present the results of a lattice QCD calculation of the scalar and vector form factors for the unphysical Bs → ηs decay, over the full physical range of q2. This is a useful testing ground both for lattice QCD and for our wider understanding of the behavior of form factors. Calculations were perf...

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Bibliographic Details
Published in:Physical review. D 2021-05, Vol.103 (9), p.1, Article 094506
Main Authors: Parrott, W. G., Bouchard, C., Davies, C. T. H., Hatton, D.
Format: Article
Language:English
Subjects:
Charm (particle physics)
Flavor (particle physics)
Form factors
Gluons
Matrix methods
Particle decay
Quantum chromodynamics
Quarks
Recoil
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Summary:We present the results of a lattice QCD calculation of the scalar and vector form factors for the unphysical Bs → ηs decay, over the full physical range of q2. This is a useful testing ground both for lattice QCD and for our wider understanding of the behavior of form factors. Calculations were performed using the highly improved staggered quark (HISQ) action on Nf = 2 + 1 + 1 gluon ensembles generated by the MILC Collaboration with an improved gluon action and HISQ sea quarks. We use three lattice spacings and a range of heavy quark masses from that of charm to bottom, all in the HISQ formalism. This permits an extrapolation in the heavy quark mass and lattice spacing to the physical point and nonperturbative renormalization of the vector matrix element on the lattice. We find results in good agreement with previous work using nonrelativistic QCD b quarks and with reduced errors at low q2, supporting the effectiveness of our heavy HISQ technique as a method for calculating form factors involving heavy quarks. A comparison with results for other decays related by SU(3) flavor symmetry shows that the impact of changing the light daughter quark is substantial but changing the spectator quark has very little effect. We also map out form factor shape parameters as a function of heavy quark mass and compare to heavy quark effective theory expectations for mass scaling at low and high recoil. This work represents an important step in the progression from previous work on heavy-to-heavy decays ( b → c ) to the numerically more challenging heavy-to-light decays.
ISSN:2470-0010
2470-0029
DOI:10.1103/PhysRevD.103.094506