Chirally improving Wilson fermions I. O(a) improvement
Abstract
We show that it is possible to improve the chiral behaviour and the approach to the continuum limit of correlation functions in lattice QCD with Wilson fermions by taking arithmetic averages of correlators computed in theories regularized with Wilson terms of opposite sign. Improved hadronic masses and matrix elements can be obtained by similarly averaging the corresponding physical quantities separately computed within the two regularizations. To deal with the problems related to the spectrum of the WilsonDirac operator, which are particularly worrisome when Wilson and mass terms are such as to give contributions of opposite sign to the real part of the eigenvalues, we propose to use twistedmass lattice QCD for the actual computation of the quantities taking part to the averages. The choice +/pi/2 for the twisting angle is particularly interesting, as O(a) improved estimates of physical quantities can be obtained even without averaging data from lattice formulations with opposite Wilson terms. In all cases little or no extra computing power is necessary, compared to simulations with standard Wilson fermions or twistedmass lattice QCD.
 Publication:

Journal of High Energy Physics
 Pub Date:
 August 2004
 DOI:
 10.1088/11266708/2004/08/007
 arXiv:
 arXiv:heplat/0306014
 Bibcode:
 2004JHEP...08..007F
 Keywords:

 Lattice Gauge Field Theories Kaon Physics Lattice QCD;
 High Energy Physics  Lattice
 EPrint:
 71 pages, Latex, Keywords: Lattice, Improvement, Chirality. Version v2: mistake corrected in transformation properties under \omega >