[Show abstract][Hide abstract] ABSTRACT: We present results for the masses of pseudoscalar mesons in twisted mass
lattice QCD with a degenerate doublet of u and d quarks and a non-degenerate
doublet of s and c quarks in the framework of next-to-leading order chiral
perturbation theory, including lattice effects up to O(a^2). The masses depend
on the two twist angles for the light and heavy sectors. For maximal twist in
both sectors, O(a)-improvement is explicitly exhibited. The mixing of
flavour-neutral mesons is also discussed, and results in the literature for the
case of degenerate s and c quarks are corrected.
Journal of High Energy Physics 03/2011; 2011(4). DOI:10.1007/JHEP04(2011)116 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present a comprehensive investigation of light meson physics using maximally twisted mass fermions for N f =2 mass-degenerate quark flavours. By employing four values of the lattice spacing, spatial lattice extents ranging from 2.0 fm to 2.5 fm and pseudo scalar masses in the range 280≲m PS ≲650 MeV we control the major systematic effects of our calculation. This enables us to confront our N f =2 data with SU(2) chiral perturbation theory and extract low energy constants of the effective chiral Lagrangian and derived quantities, such as the light quark mass.
Journal of High Energy Physics 08/2010; 2010(8). DOI:10.1007/JHEP08(2010)097 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The latest results of an ongoing project for the lattice simulation of QCD with a single quark flavor are presented. The Symanzik tree-level-improved Wilson action is adopted in the gauge sector and the (unimproved) Wilson action for the fermion. Results from new simulations with one step of Stout-smearing (rho=0.15) in the fermion action are discussed. The one-flavor theory is simulated by a polynomial hybrid Monte Carlo algorithm (PHMC) at beta=4.0 corresponding to a = 0.13fm, on 16^3x32 and 24^3x48 lattices; the box-size is L = 2.1fm and L = 3.1fm, respectively. At the lightest simulated quark mass the (partially quenched) pion mass is ~300 MeV. The masses of the lightest bound states are computed, including the flavor singlet scalar and pseudoscalar mesons sigma_s and eta_s, the scalar glueball 0^++, and the Delta^++ baryon. Relics of SUSY in the mass spectrum, expected from a large N_c orientifold equivalence with the N=1 supersymmetric Yang-Mills theory, are discussed. Comment: 7 pages, 2 figures, talk presented at the XXVI International Symposium on Lattice Field Theory, July 14-19, 2008, Williamsburg, Virginia, USA
[Show abstract][Hide abstract] ABSTRACT: In a recent paper [ETMC, P. Boucaud et al., Phys. Lett. B 650 (2007) 304, hep-lat/0701012] we presented precise lattice QCD results of our European Twisted Mass Collaboration (ETMC). They were obtained by employing two mass-degenerate flavours of twisted mass fermions at maximal twist. In the present paper we give details on our simulations and the computation of physical observables. In particular, we discuss the problem of tuning to maximal twist, the techniques we have used to compute correlators and error estimates. In addition, we provide more information on the algorithm used, the autocorrelation times and scale determination, the evaluation of disconnected contributions and the description of our data by means of chiral perturbation theory formulae.
[Show abstract][Hide abstract] ABSTRACT: The hadron spectrum of one flavor QCD is studied by Monte Carlo simulations. The Symanzik tree-level-improved Wilson action is used for the gauge field and the Wilson action for the fermion. The theory is simulated by a polynomial hybrid Monte Carlo algorithm (PHMC). The mass spectrum of hadronic bound states is investigated at two different lattice spacings: a ~ 0.37r_0 and a ~ 0.27r_0, corresponding to ~0.19fm and ~0.13fm in ordinary QCD. The lattice extension is fixed to L ~ 4.4r_0 (~2.2fm). The lightest simulated quark mass corresponds to a pion with mass ~270MeV. Properties of the theory are analyzed by making use of the ideas of partially quenched chiral perturbation theory (PQChPT). The symmetry of the single flavor theory can be artificially enhanced by adding extra valence quarks, which can be interpreted as u and d quarks. Operators in the valence pion sector can be built. Masses and decay constants are analyzed by using PQChPT formulae at next-to-leading order. Comment: 14 pages, 4 figures; Proceedings of the XXV International Symposium on Lattice Field Theory "Lattice 2007", Regensburg, Germany
[Show abstract][Hide abstract] ABSTRACT: One-flavour QCD – a gauge theory with SU(3) colour gauge group and a fermion in the fundamental representation – is studied
by Monte Carlo simulations. The mass spectrum of the hadronic bound states is investigated in a volume with extensions of
L≃4.4r0 (≃ 2.2fm) at two different lattice spacings: a≃0.37r0 (≃ 0.19fm) and a≃0.27r0 (≃ 0.13fm). The lattice action is a Symanzik tree-level improved Wilson action for the gauge field and an (unimproved) Wilson
action for the fermion.
European Physical Journal C 09/2007; 52(2):305-314. DOI:10.1140/epjc/s10052-007-0394-4 · 5.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Quantum Chromodynamics on a lattice with Wilson fermions and a chirally twisted mass term is considered in the framework of chiral perturbation theory. For two and three numbers of quark flavours, respectively, with non-degenerate quark masses the pseudoscalar meson masses and decay constants are calculated in next-to-leading order including lattice effects quadratic in the lattice spacing a. Comment: 9 pages, LaTeX2e, reference added
Journal of High Energy Physics 03/2006; 2006(8). DOI:10.1088/1126-6708/2006/08/085 · 6.11 Impact Factor