Renormalizing vector currents in lattice QCD using momentum-subtraction schemes

Hatton, D., Davies, C.T.H. , Lepage, G.P. and Lytle, A.T. (2019) Renormalizing vector currents in lattice QCD using momentum-subtraction schemes. Physical Review D, 100(11), 114513. (doi: 10.1103/PhysRevD.100.114513)

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We examine the renormalization of flavor-diagonal vector currents in lattice QCD with the aim of understanding and quantifying the systematic errors from nonperturbative artifacts associated with the use of intermediate momentum-subtraction schemes. Our study uses the highly improved staggered quark action on gluon-field configurations that include n f = 2 + 1 + 1 flavors of sea quarks, but our results have applicability to other quark actions. Renormalization schemes that make use of the exact lattice vector Ward-Takahashi identity for the conserved current also have renormalization factors, Z V , for nonconserved vector currents that are free of contamination by nonperturbative condensates. We show this by explicit comparison of two such schemes: that of the vector form factor at zero momentum transfer and the RI-SMOM momentum-subtraction scheme. The two determinations of Z V differ only by discretization effects (for any value of momentum transfer in the RI-SMOM case). The RI ′ -MOM scheme, although widely used, does not share this property. We show that Z V determined in the standard way in this scheme has O ( 1 % ) nonperturbative contamination that limits its accuracy. Instead we define an RI ′ -MOM Z V from a ratio of local to conserved vector current vertex functions and show that this Z V is a safe one to use in lattice QCD calculations. We also perform a first study of vector current renormalization with the inclusion of quenched QED effects on the lattice using the RI-SMOM scheme.

Item Type:Articles
Additional Information:Authors for the HPWCD Collaboration. Funded by SCOAP3.
Glasgow Author(s) Enlighten ID:Lytle, Dr Andrew and Hatton, Dr Daniel and Davies, Professor Christine
Authors: Hatton, D., Davies, C.T.H., Lepage, G.P., and Lytle, A.T.
College/School:College of Science and Engineering > School of Physics and Astronomy
Research Group:HPQCD Collaboration
Journal Name:Physical Review D
Publisher:American Physical Society
ISSN (Online):2470-0029
Published Online:20 December 2019

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