Non-perturbative renormalization of quark bilinear operators with Nf=2 (tmQCD) Wilson fermions and the tree-level improved gauge action

TL;DR

This paper computes non-perturbative renormalization constants for quark bilinear operators using improved gauge and twisted mass fermion actions, employing the RI-MOM scheme and addressing discretization effects.

Contribution

It provides the first detailed non-perturbative renormalization constants for Nf=2 twisted mass fermions with improved gauge action, including subtraction of discretization effects.

Findings

Renormalization constants ZV, ZA, ZP/ZS computed with RI-MOM and alternative methods.

Explicit subtraction of O(g^2 a^2) discretization effects.

Results applicable to both twisted mass and standard Wilson fermions.

Abstract

We present results for the renormalization constants of bilinear quark operators obtained by using the tree-level Symanzik improved gauge action and the Nf=2 twisted mass fermion action at maximal twist, which guarantees automatic O(a)-improvement. Our results are also relevant for the corresponding standard (un-twisted) Wilson fermionic action since the two actions only differ, in the massless limit, by a chiral rotation of the quark fields. The scale-independent renormalization constants ZV, ZA and the ratio ZP/ZS have been computed using the RI-MOM approach, as well as other alternative methods. For ZA and ZP/ZS, the latter are based on both standard twisted mass and Osterwalder-Seiler fermions, while for ZV a Ward Identity has been used. The quark field renormalization constant Zq and the scale dependent renormalization constants ZS, ZP and ZT are determined in the RI-MOM scheme. Leading discretization effects of O(g^2 a^2), evaluated in one-loop perturbation theory, are explicitly subtracted from the RI-MOM estimates.