A. Shindler

Dynamical Twisted Mass Fermions with Light Quarks: Simulation and Analysis Details

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.

Light Meson Physics from Maximally Twisted Mass Lattice QCD

We present a comprehensive investigation of light meson physics using maximally twisted mass fermions for Nf = 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 ≲ mPS ≲ 650MeV we control the major systematic effects of our calculation. This enables us to confront our Nf = 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.

Dynamical twisted mass fermions with light quarks

We present results of dynamical simulations with 2 flavours of degenerate Wilson twisted mass quarks at maximal twist in the range of pseudo scalar masses from 300 to 550 MeV. The simulations are performed at one value of the lattice spacing a lesssim 0.1 fm. In order to have O(a) improvement and aiming at small residual cutoff effects, the theory is tuned to maximal twist by requiring the vanishing of the untwisted quark mass. Precise results for the pseudo scalar decay constant and the pseudo scalar mass are confronted with chiral perturbation theory predictions and the low energy constants F, bar{l}_3 and bar{l}_4 are evaluated with small statistical errors.

HMC algorithm with multiple time scale integration and mass preconditioning

Abstract We present a variant of the HMC algorithm with mass preconditioning (Hasenbusch acceleration) and multiple time scale integration. We have tested this variant for standard Wilson fermions at β = 5.6 and at pion masses ranging from 380 to 680 MeV. We show that in this situation its performance is comparable to the recently proposed HMC variant with domain decomposition as preconditioner. We give an update of the “Berlin Wall” figure, comparing the performance of our variant of the HMC algorithm to other published performance data. Advantages of the HMC algorithm with mass preconditioning and multiple time scale integration are that it is straightforward to implement and can be used in combination with a wide variety of lattice Dirac operators.

On lattice actions for static quarks

We introduce new discretizations of the action for static quarks. They achieve an exponential improvement (compared to the Eichten-Hill regularization) on the signal to noise ratio in static-light correlation functions. This is explicitly checked in a quenched simulation and it is understood quantitatively in terms of the self energy of a static quark and the lattice heavy quark potential at zero distance. We perform a set of scaling tests in the Schroedinger functional and find scaling violations in the O(a) improved theory to be rather small -- for one observable significantly smaller than with the Eichten-Hill regularization. In addition we compute the improvement coefficients of the static light axial current up to O(g_0^4) corrections and the corresponding renormalization constants non-perturbatively. The regularization dependent part of the renormalization of the b-quark mass in static approximation is also determined.

B-physics from Nf = 2 tmQCD: the Standard Model and beyond

A bstractWe present a lattice QCD computation of the b-quark mass, the B and Bs decay constants, the B-mixing bag prameters for the full four-fermion operator basis as well as determinations for ξ and fBq

Pseudoscalar decay constants of kaon and D-mesons from N f = 2 twisted mass Lattice QCD

sqrt{{B_i^{(q) }}}

Light quark masses and pseudoscalar decay constants from Nf = 2 lattice QCD with twisted mass fermions

extrapolated to the continuum limit and to the physical pion mass. We used Nf = 2 twisted mass Wilson fermions at four values of the lattice spacing with pion masses ranging from 280 to 500 MeV. Extrapolation in the heavy quark mass from the charm to the bottom quark region has been carried out on ratios of physical quantities computed at nearby quark masses, exploiting the fact that they have an exactly known infinite mass limit. Our results are mb(mb,

Light baryon masses with dynamical twisted mass fermions

overline{mathrm{MS}}

Twisted mass quarks and the phase structure of lattice QCD

) = 4.29(12) GeV, fBs = 228(8) MeV, fB = 189(8) MeV and fBs/fB = 1.206(24). Moreover with our results for the bag-parameters we find ξ = 1.225(31),