arXiv subjects
Publications and source records attributed to George T. Fleming.
We compute the pion electromagnetic form factor in a hybrid calculation with domain wall valence quarks and improved staggered (asqtad) sea quarks. This method can easily be extended to rho-to-gamma-pi transition form factors.
We present preliminary results for $ε'/ε$ calculated using HYP staggered fermions in the quenched approximation. We compare different choices of quenched penguin operators.
We have started a program to compute the electromagnetic form factors of mesons. We discuss the techniques used to compute the pion form factor and present preliminary results computed with domain wall valence fermions on MILC asqtad lattices, as well as Wilson fermions on quenched lattices. These methods can easily be extended to rho-to-gamma-pi transition form factors.
A ratio of lattice correlation functions is identified from which the pion form factor can be obtained directly. Preliminary results from quenched Wilson simulations are presented.
A different lattice fermion method is introduced. Staggered domain wall fermions are defined in 2n+1 dimensions and describe 2^n flavors of light lattice fermions with exact U(1) x U(1) chiral symmetry in 2n dimensions. As the size of the extra dimension becomes large, 2^n chiral flavors with the same chiral charge are expected to be localized on each boundary and the full SU(2^n) x SU(2^n) flavor chiral symmetry is expected to be recovered. SDWF give a different perspective into the inherent flavor mixing of lattice fermions and by design present an advantage for numerical simulations of lattice QCD thermodynamics. The chiral and topological index properties of the SDWF Dirac operator are investigated. And, there is a surprise ending...
Last year, we reported our first results on the determination of Gasser-Leutwyler coefficients using partially quenched lattice QCD with three flavors of dynamical staggered quarks. We give an update on our progress in determining two of these coefficients, including an exhaustive effort to estimate all sources of systematic error. At this conference, we have heard about algorithmic techniques to reduce staggered flavor symmetry breaking and a method to incorporate staggered flavor breaking into the partially quenched chiral Lagrangian. We comment on our plans to integrate these developments into our ongoing program.
A standing mystery in the Standard Model is the unnatural smallness of the strong CP violating phase. A massless up quark has long been proposed as one potential solution. A lattice calculation of the constants of the chiral Lagrangian essential for the determination of the up quark mass, 2 alpha_8 - alpha_5, is presented. We find 2 alpha_8 - alpha_5 = 0.29 +/- 0.18, which corresponds to m_u / m_d = 0.410 +/- 0.036. This is the first such calculation using a physical number of dynamical light quarks, N_f = 3.
The behavior of staggered domain wall fermions in the presence of gauge fields is presented. In particular, their response to gauge fields with nontrivial topology is discussed.
Several lattice calculations of a combination of the low energy constants of the chiral Lagrangian, 2α_8-α_5, are presented. This combination is critical for the preclusion of a massless up quark. The result found is 2α_8-α_5 = 0.115 \pm 0.051^{stat} \pm 0.25^{syst}, which is well outside of the range allowed by a massless up quark.
Supersymmetry, like Poincare symmetry, is softly broken at finite lattice spacing provided the gaugino mass term is strongly suppressed. Domain wall fermions provide the mechanism for suppressing this term by approximately imposing chiral symmetry. We present the first numerical simulations of N=1 supersymmetric SU(2) Yang-Mills on the lattice in four dimensions using domain wall fermions.
Supersymmetry, like Poincare symmetry, is softly broken at finite lattice spacing provided the gaugino mass term is strongly suppressed. Domain wall fermions provide the mechanism for suppressing this term by approximately imposing chiral symmetry on the lattice. We present the first numerical simulations of N=1 supersymmetric SU(2) Yang-Mills on the lattice in d=4 dimensions using domain wall fermions.
Studies of non-interacting lattice fermions give an estimate of the size of discretization errors and finite size effects for more interesting problems like finite temperature QCD. We present a calculation of the thermodynamic equation of state for free domain wall and overlap fermions.
We present results from simulations of two flavor QCD thermodynamics at N_t=4 with domain wall fermions. In contrast to other lattice fermion formulations, domain wall fermions preserve the full chiral symmetry of the continuum at finite lattice spacing (up to terms exponentially small in an extra parameter). Just above the phase transition, we find that the axial U(1) symmetry is broken only by a small amount. We discuss an ongoing calculation to determine the order and properties of the phase transition using domain wall fermions, since the global symmetries of the theory are expected to be important here.