Physics Letters B 804 (2020) 135398
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Bilinear quark operators in the RI/SMOM scheme at three loops
Bernd A. Kniehl
a,∗
, Oleg L. Veretin
b
a
II. Institut für Theoretische Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
b
Institut für Theoretische Physik, Universität Regensburg, Universitätsstraße 31, 93040 Regensburg, Germany
a r t i c l e i n f o a b s t r a c t
Article history:
Received 21 February 2020
Accepted 23 March 2020
Available online 26 March 2020
Editor: B. Grinstein
Keywords:
Lattice QCD
Bilinear quark operators
MS scheme
Regularization invariant symmetric MOM
scheme
Three-loop approximation
We consider the renormalization of the matrix elements of the bilinear quark operators
¯
ψψ
,
¯
ψ
γ
μ
ψ,
and
¯
ψ
σ
μν
ψ at next-to-next-to-next-to-leading order in QCD perturbation theory at the symmetric
subtraction point. This allows us to obtain conversion factors between the MS scheme and the
regularization invariant symmetric momentum subtraction (RI/SMOM) scheme. The obtained results can
be used to reduce the errors in determinations of quark masses from lattice QCD simulations. The results
are given in Landau gauge.
© 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP
3
.
1. Introduction
The lattice formulation of quantum chromodynamics (QCD) provides a possibility to estimate long-distance operator matrix elements
from first principles using Monte Carlo methods. Many important physical observables can be related to matrix elements of bilinear quark
operators of the form O
μ...ν
=
¯
ψ
μ...ν
ψ, where
μ...ν
is some Dirac structure that can contain covariant derivatives.
We start from the following expression in Minkowski space:
dxd y e
−iq·x−ip · y
ψ
ξ,i
(x) O
μ...ν
(0)
¯
ψ
ζ,j
(y)=δ
ij
S
ξξ
(−q)
ξ
ζ
(p, q)S
ζ
ζ
(p), (1)
where ξ, ζ are spinor indices, i, j are color indices in the fundamental representation, S(q) is the quark propagator, and (p, q) is the
amputated Green’s function, which is shown schematically in Fig. 1.
The renormalization of the matrix elements on the lattice is done in some appropriate renormalization scheme. One of the popular
schemes is the regularization independent momentum subtraction (RI/MOM) scheme or its variant, the RI
/MOM scheme [1], where the
Fig. 1. Matrix element ψ(q) O (−q − p)
¯
ψ(
p) of a bilinear quark operator in momentum space. The black box denotes the operator, and solid lines denote the external
quarks.
*
Corresponding author.
E-mail addresses: kniehl@desy.de (B.A. Kniehl),
oleg.veretin@desy.de (O.L. Veretin).
https://doi.org/10.1016/j.physletb.2020.135398
0370-2693/© 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by
SCOAP
3
.