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Title: O(a^2) corrections to 1-loop matrix elements of 4-fermion operators with improved fermion/gluon actions
Authors: Constantinou, Martha
Lubicz, Vittorio
Panagopoulos, Haralambos
Skouroupathis, Apostolos
Stylianou, Fotos
Keywords: Lattice QCD
Issue Date: 2009
Publisher: PoS - Proceedings of Science
Pages: 260
Abstract: We calculate the corrections to the amputated Green's functions of 4-fermion operators, in 1-loop Lattice Perturbation theory. The novel aspect of our calculations is that they are carried out to second order in the lattice spacing, O(a^2). We employ the Wilson/clover action for massless fermions (also applicable for the twisted mass action in the chiral limit) and the Symanzik improved action for gluons. Our calculations have been carried out in a general covariant gauge. Results have been obtained for several popular choices of values for the Symanzik coefficients (Plaquette, Tree-level Symanzik, Iwasaki, TILW and DBW2 action). We pay particular attention to Delta F=2 operators, both Parity Conserving and Parity Violating (F stands for flavour: S, C, B). We study the mixing pattern of these operators, to O(a^2), using the appropriate projectors. Our results for the corresponding renormalization matrices are given as a function of a large number of parameters: coupling constant, clover parameter, number of colors, lattice spacing, external momentum and gauge parameter. The O(a^2) correction terms (along with our previous O(a^2) calculation of Z_Psi) are essential ingredients for minimizing the lattice artifacts which are present in non-perturbative evaluations of renormalization constants with the RI'-MOM method. A longer write-up of this work, including non-perturbative results, is in preparation together with members of the ETM Collaboration.
Appears in Collections:X_Dipartimento di Fisica 'Edoardo Amaldi'
ATC - Atti di Convegno

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