Article
Scaling behavior and sea quark dependence of pion spectrum with HYPsmeared staggered fermions
09/2008;
Source: arXiv
 Citations (5)
 Cited In (0)

Article: UKQCD Collaboration
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ABSTRACT: We extend our previous study of magnetic monopole currents in the max imally Abelian gauge (1) to larger lattices at small lattice spacings (204 at � = 2.5 and 324 at � = 2.5115). We confirm that at these weak couplings there continues to be one monopole cluster that is very much longer than the rest and that the string tension, K, is entirely due to it. The remaining clus ters are compact objects whose population as a function of radius follows a power law that deviates from the scale invariant form, but much too weakly to suggest a link with the analytically calculable size distribution of small instantons. We also search for traces of Z(2) vortices in the Abelian pro jected fields; either as closed loops of 'magnetic' flux or through appropriate correlations amongst the monopoles. We find, by direct calculation, that there is no confining condensate of such flux loops. We also find, through the calculation of doubly charged Wilson loops within the monopole fields, that there is no suppression of the q = 2 effective string tension out to at distances of at least r ≃ 1.6/ √ K, suggesting that if there are any vortices  [show abstract] [hide abstract]
ABSTRACT: We study the impact of hypercubic (HYP) smearing on the size of tastebreaking for staggered fermions, comparing to unimproved and to asqtadimproved staggered fermions. As in previous studies, we find a substantial reduction in tastebreaking compared to unimproved staggered fermions (by a factor of 4–7 on lattices with spacing a≈0.1 fm). In addition, we observe that discretization effects of nexttoleading order in the chiral expansion (O(a2p2)) are markedly reduced by HYP smearing. Compared to asqtad valence fermions, we find that tastebreaking in the pion spectrum is reduced by a factor of 2.5–3, down to a level comparable to the expected size of generic O(a2) effects. Our results suggest that, once one reaches a lattice spacing of a≈0.09 fm, tastebreaking will be small enough after HYP smearing that one can use a modified power counting in which O(a2)≪O(p2), simplify fitting to phenomenologically interesting quantities.Physical review D: Particles and fields 05/2008; 77(9).  [show abstract] [hide abstract]
ABSTRACT: We use perturbative Symanzik improvement to create a new staggeredquark action (HISQ) that has greatly reduced oneloop tasteexchange errors, no treelevel order a^2 errors, and no treelevel order (am)^4 errors to leading order in the quark's velocity v/c. We demonstrate with simulations that the resulting action has tasteexchange interactions that are at least 34 times smaller than the widely used ASQTAD action. We show how to estimate errors due to taste exchange by comparing ASQTAD and HISQ simulations, and demonstrate with simulations that such errors are no more than 1% when HISQ is used for light quarks at lattice spacings of 1/10 fm or less. The suppression of (am)^4 errors also makes HISQ the most accurate discretization currently available for simulating c quarks. We demonstrate this in a new analysis of the psieta_c mass splitting using the HISQ action on lattices where a m_c=0.43 and 0.66, with fullQCD gluon configurations (from MILC). We obtain a result of~111(5) MeV which compares well with experiment. We discuss applications of this formalism to D physics and present our first highprecision results for D_s mesons.Physical review D: Particles and fields 11/2006;
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