5,401 research outputs found
Flavor Physics and Lattice QCD
Our ability to resolve new physics effects is, largely, limited by the
precision with which we calculate. The calculation of observables in the
Standard (or a new physics) Model requires knowledge of associated hadronic
contributions. The precision of such calculations, and therefore our ability to
leverage experiment, is typically limited by hadronic uncertainties. The only
first-principles method for calculating the nonperturbative, hadronic
contributions is lattice QCD. Modern lattice calculations have controlled
errors, are systematically improvable, and in some cases, are pushing the
sub-percent level of precision. I outline the role played by, highlight state
of the art efforts in, and discuss possible future directions of lattice
calculations in flavor physics.Comment: Invited review of lattice QCD in quark and lepton flavor physics.
Presentation at the DPF 2013 Meeting of the American Physical Society
Division of Particles and Fields, Santa Cruz, California, August 13-17, 201
form factors from lattice QCD
We report the first lattice QCD calculation of the form factors for the
standard model tree-level decay . In combination with future
measurement, this calculation will provide an alternative exclusive
semileptonic determination of . We compare our results with previous
model calculations, make predictions for differential decay rates and branching
fractions, and predict the ratio of differential branching fractions between
and . We also present standard model
predictions for differential decay rate forward-backward asymmetries,
polarization fractions, and calculate potentially useful ratios of
form factors with those of the fictitious decay. Our lattice
simulations utilize NRQCD and HISQ light quarks on a subset of the MILC
Collaboration's asqtad gauge configurations, including two lattice
spacings and a range of light quark masses.Comment: 24 pages, 21 figures; Ver. 2 matches published versio
B and Bs semileptonic decay form factors with NRQCD/HISQ quarks
We discuss our ongoing effort to calculate form factors for several B and Bs
semileptonic decays. We have recently completed the first unquenched
calculation of the form factors for the rare decay B -> K ll. Extrapolated over
the full kinematic range of q^2 via model-independent z expansion, these form
factor results allow us to calculate several Standard Model observables. We
compare with experiment (Belle, BABAR, CDF, and LHCb) where possible and make
predictions elsewhere. We discuss preliminary results for Bs -> K l nu which,
when combined with anticipated experimental results, will provide an
alternative exclusive determination of |Vub|. We are exploring the possibility
of using ratios of form factors for this decay with those for the unphysical
decay Bs -> eta_s as a means of significantly reducing form factor errors. We
are also studying B -> pi l nu, form factors for which are combined with
experiment in the standard exclusive determination of |Vub|. Our simulations
use NRQCD heavy and HISQ light valence quarks on the MILC 2+1 dynamical asqtad
configurations.Comment: 7 pages, 5 figures, presented at the 31st International Symposium on
Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German
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