Roland Hoffmann

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A non–perturbative determination of the axial current improvement coefficient cA is performed with two flavors of dynamical improved Wilson fermions and plaquette gauge action. The improvement condition is formulated with Schrödinger functional boundary conditions and enforced at constant physical volume. Large sensitivity is obtained by using two different(More)
The realization of global symmetries can depend on the geometry of the underlying space. In particular, compactification can lead to spontaneous breaking of such symmetries. Four–dimensional QCD with fundamental representation fermions embedded in a space with one compact spatial dimension has a critical length, at which the theory undergoes a phase(More)
The running of renormalized quark masses is computed in lattice QCD with two massless O(a) improved Wilson quarks. The regularization and flavor independent factor that relates running quark masses to the renormalization group invariant ones is evaluated in the Schrödinger Functional scheme. Using existing data for the scale r0 and the pseudoscalar meson(More)
We present a new normalization condition for the axial current, derived from the PCAC relation with non–vanishing quark mass. This condition is expected to reduce mass effects in the chiral extrapolation of the results for the normalization factor ZA. The application to the two–flavor theory with improved Wilson fermions shows that this expectation is(More)
Large cutoff effects of dynamical Wilson fermions ∗ R. Sommer, S. Aoki, M. Della Morte, R. Hoffmann, T. Kaneko, F. Knechtli, J. Rolf, I. Wetzorke and U. Wolff (ALPHA, CP-PACS and JLQCD Collaborations) DESY Zeuthen, Platanenallee 6, 15738 Zeuthen, Germany CERN–TH, CH–1211 Geneva 23, Switzerland Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki(More)
Accurate measurement of neutrino energies is essential to many of the scientific goals of large-volume neutrino telescopes. The fundamental observable in such detectors is the Cherenkov light produced by the transit through a medium of charged particles created in neutrino interactions. The amount of light emitted is proportional to the deposited energy,(More)
Using Schrödinger functional techniques, we determine the coefficient of the clover term necessary for non-perturbative O(a) improvement of hypercubic smeared Wilson fermions on a quenched plaquette action background. Unlike for unsmeared Wilson fermions, the resulting clover coefficients are close to the tree–level value even at coarse lattice spacings,(More)
Evidence for an extraterrestrial flux of high-energy neutrinos has now been found in multiple searches with the IceCube detector. The first solid evidence was provided by a search for neutrino events with deposited energies 30  TeV and interaction vertices inside the instrumented volume. Recent analyses suggest that the extraterrestrial flux extends to(More)
We compute the topological susceptibility χt in SU(3) lattice gauge theory using fermionic methods based on the Atiyah-Singer index theorem. Near the phase transition we find a smooth crossover behavior for χt with values decreasing from (191(5) MeV) 4 to (100(5) MeV) as we increase the temperature from 0.88 Tc to 1.31 Tc, showing that topological(More)