On the flavour interpretations of staggered fermions (original) (raw)

Self-energy and flavor interpretation of staggered fermions

Nuclear Physics B, 1984

We investigate the symmetries of the staggered fermlon formulation and the construchon of local hadron fields on the lattice The one-loop fermlon self-energy ~s calculated w~th a general non-degenerate mass matrix and the ~mphcatlons of the results are discussed

The flavour projection of staggered fermions and the quarter-root trick

Journal of High Energy Physics, 2007

It is shown that the flavour projection of staggered fermions can be written as a projection between the fields on four separate, but parallel, lattices, where the fields on each are modified forms of the standard staggered fermion field. Because the staggered Dirac operator acts equally on each lattice, it respects this flavour projection. We show that the system can be gauged in the usual fashion and that this does not interfere with flavour projection. We also consider the path integral, showing that, prior to flavour projection, it evaluates to the same form on each lattice and that this form is equal to that used in the quarter-root trick. The flavour projection leaves a path integral for a single flavour of field on each lattice.

Probing technicolor theories with staggered fermions

Arxiv preprint arXiv: …, 2008

One exciting possibility of new physics beyond the Standard Model is that the fundamental Higgs sector is replaced by a strongly-interacting gauge theory, known as technicolor. A viable theory must break chiral symmetry dynamically, like in QCD, to generate Goldstone bosons which become the longitudinal components of the W ± and Z. By measuring the eigenvalues of the Dirac operator, one can determine if chiral symmetry is in fact spontaneously broken. We simulate SU(3) gauge theory with n s = 2 and 3 staggered flavors in the fundamental representation, corresponding to N f = 8 and 12 flavors in the continuum limit. Although our first findings show that both theories are consistent with dynamically broken chiral symmetry and QCD-like behavior, flavor breaking effects in the spectrum may require further clarifications before final conclusions can be drawn. We also compare various improved staggered actions, to suppress this potentially large flavor breaking. Figure 1: The conformal window for SU(N) gauge theories with N f techniquarks in various representations, from [3]. The shaded regions are the windows, for fundamental (gray), 2-index antisymmetric (blue), 2-index symmetric (red) and adjoint (green) representations.

Flavor constraints on split fermion models

Physical Review D, 2003

We examine the contributions to rare processes that arise in models where the Standard Model fermions are localized at distinct points in compact extra dimensions. Tree-level flavor changing neutral current interactions for the Kaluza-Klein (KK) gauge field excitations are induced in such models, and hence strong constraints are thought to exist on the size of the additional dimensions. We find a general parameterization of the model which does not depend on any specific fermion geography and show that typical values of the parameters can reproduce the fermion hierarchy pattern. Using this parameterization, we reexamine the contributions to neutral meson mixing, rare meson decays, and single top-quark production in e+e−e^+e^-e+e− collisions. We find that is it possible to evade the stringent bounds for natural regions of the parameters, while retaining finite separations between the fermion fields and without introducing a new hierarchy. The resulting limits on the size of the compact dimension can be as low as TeV$^{-1}$.

The QCD equation of state from improved staggered fermions

2009

We calculate the equation of state in 2+1 flavor QCD at finite temperature with physical strange quark mass and almost physical light quark masses using lattices with temporal extent Ntau=8N_{\tau}=8Ntau=8. Calculations have been performed with two different improved staggered fermion actions, the asqtad and p4 actions. Overall, we find good agreement between results obtained with these two O(a2)O(a^2)O(a2) improved staggered fermion discretization schemes. A comparison with earlier calculations on coarser lattices is performed to quantify systematic errors in current studies of the equation of state. We also present results for observables that are sensitive to deconfining and chiral aspects of the QCD transition on Ntau=6N_\tau=6Ntau=6 and 8 lattices. We find that deconfinement and chiral symmetry restoration happen in the same narrow temperature interval.

The phase diagram of QCD with two and four flavors: results with HYP fermions

Nuclear Physics B - Proceedings Supplements, 2002

We study the finite temperature phase transition of four and two flavor staggered fermions with hypercubic smeared link actions. These preliminary studies suggest that the improved flavor symmetry of the fermionic action can have a significant effect on the finite temperature phase diagram.