Accelerating Hasenbusch's acceleration of Hybrid Monte Carlo

Hasenbusch has proposed splitting the pseudo-fermionic action into two parts, in order to speed-up Hybrid Monte Carlo simulations of QCD. We have tested a different splitting, also using clover-improved Wilson fermions. An additional speed-up between 5 and 20% over the original proposal was achieved in production runs.Comment: Poster presented by H. Stueben at Lattice2003, meta-data correcte

Quark structure from the lattice Operator Product Expansion

We have reported elsewhere in this conference on our continuing project to determine non-perturbative Wilson coefficients on the lattice, as a step towards a completely non-perturbative determination of the nucleon structure. In this talk we discuss how these Wilson coefficients can be used to extract Nachtmann moments of structure functions, using the case of off-shell Landau-gauge quarks as a first simple example. This work is done using overlap fermions, because their improved chiral properties reduce the difficulties due to operator mixing.Comment: 7 pages, 3 figures. Talk given at the XXVII International Symposium on Lattice Field Theory, July 26-31 2009, Peking University, Beijing, Chin

The nucleon mass in N_f=2 lattice QCD: finite size effects from chiral perturbation theory

In the framework of relativistic SU(2)_f baryon chiral perturbation theory we calculate the volume dependence of the nucleon mass up to and including O(p^4). Since the parameters in the resulting finite size formulae are fixed from the pion mass dependence of the large volume nucleon masses and from phenomenology, we obtain a parameter-free prediction of the finite size effects. We present mass data from the recent N_f=2 simulations of the UKQCD and QCDSF collaborations and compare these data as well as published mass values from the dynamical simulations of the CP-PACS and JLQCD collaborations with the theoretical expectations. Remarkable agreement between the lattice data and the predictions of chiral perturbation theory in a finite volume is found.Comment: 23 pages, 5 figures; references added + minor corrections; one more reference added, typo in eq.(25) corrected, additional clarifying remark

Axial and tensor charge of the nucleon with dynamical fermions

We present preliminary results for the axial and tensor charge of the nucleon obtained from simulations with N_f=2 clover fermions. A comparison with chiral perturbation theory is attempted.Comment: Talk presented at Lattice2004(weak), Fermilab, June 21-26, 2004, 3 pages, 3 figures, v2: one reference added, v3: acknowledgement extende

Finite volume corrections to the electromagnetic current of the nucleon

We compute corrections to both the isovector anomalous magnetic moment and the isovector electromagnetic current of the nucleon to $O(p^3)$ in the framework of covariant two-flavor Baryon Chiral Perturbation Theory. We then apply these corrections to lattice data for the anomalous magnetic moment from the LHPC, RBC & UKQCD and QCDSF collaborations

The axial charge of the nucleon on the lattice and in chiral perturbation theory

We present recent Monte Carlo data for the axial charge of the nucleon obtained by the QCDSF-UKQCD collaboration for N_f=2 dynamical quarks. We compare them with formulae from chiral perturbation theory in finite and infinite volume and find a remarkably consistent picture.Comment: 6 pages, 3 figures, talk presented at Lattice2005 (weak matrix elements), needs PoS.cl

Nucleon electromagnetic form factors on the lattice and in chiral effective field theory

We compute the electromagnetic form factors of the nucleon in quenched lattice QCD, using non-perturbatively improved Wilson fermions, and compare the results with phenomenology and chiral effective field theory