Speaker
Dr
Kim Maltman
(York University)
Description
The determination of V_us via finite energy sum rule analyses of flavor-breaking combinations of non-strange and strange hadronic tau decay data yields values of V_us ~3 sigma below both expectations based on 3-family unitarity and results obtained from analyses of Gamma[K_{ell 3}] and Gamma[K_{mu 2}]/Gamma[pi_{mu 2}]. A key issue in understanding whether this low value represents new physics or just an underestimate of the uncertainties in the existing analyses is the very slow convergence of the leading D=2 contribution to the OPE representation of the relevant flavor-breaking correlator difference. A sign of this slow convergence is the fact that switching from the "local scale" CIPT prescription to the "fixed scale" FOPT prescription for the relevant D=2 contour integrals leads to results for V_us differing by an amount ~0.0020 much larger than most total theory error estimates existing in the literature. Here we investigate the issue of which (if either) of the two prescriptions for the D=2 series is more reliable by studying lattice data for the relevant correlator differences, obtained using RBC/UKQCD n_f=2+1 domain wall fermion ensembles covering a range of light quark masses and lattice spacings. We then use the lessons learned from this comparison to improve and update two flavor-breaking sum rule determination of V_us.
Summary
We describe a lattice investigation focussed on understanding how to best treat the very slowly converging D=2 OPE series entering flavor-breaking correlator combinations relevant to the determination of V_us from hadronic tau decay data.
Primary author
Dr
Kim Maltman
(York University)
Co-authors
Dr
Eoin Kerrane
(Universidad Aut\`onoma de Madrid)
Dr
James Zanotti
(University of Adelaide)
Dr
Luigi Del Debbio
(University of Edinburgh)
Dr
Nicholas Garron
(Trinity College, Dublin)
Dr
P. A. Boyle
(University of Edinburgh)
Mr
R.J. Hudspith
(University of Edinburgh)
