Thu·Sep 29, 2005Thursday·September 29, 2005

1. 01*

   Scaling behavior of discretization errors in renormalization and improvement constants

   Tanmoy Bhattacharya🇺🇸 · Rajan Gupta🇺🇸 · Weonjong Lee🇰🇷 · Stephen R. Sharpe🇺🇸

   Non-perturbative results for improvement and renormalization constants needed for on-shell and off-shell O(a) improvement of bilinear operators composed of Wilson fermions are presented. The calculations have been done in the quenched approximation at beta=6.0, 6.2 and 6.4. To quantify residual discretization errors we compare our data with results from other non-perturbative calculations and with one-loop perturbation theory.

   hep-latPRD(2006)·14 citations
2. 02*

   B_s meson excited states from the lattice

   UKQCD Collaboration · A. M. Green · J. Ignatius · M. Jahma · J. Koponen · C. McNeile · C. Michael

   This is a follow-up to our earlier work [Phys. Rev. D 65, 014512 (2002); Eur. Phys. J. C 28, 79 (2003); Phys. Rev. D 69, 094505 (2004)] for the energies and the charge (vector) and matter (scalar) distributions for S-wave states in a heavy-light meson, where the heavy quark is static and the light quark has a mass about that of the strange quark. We study the radial distributions of higher angular momentum states, namely P- and D-wave states. In nature the closest equivalent of this heavy-light system is the B_s meson. The calculation is carried out with dynamical fermions on a 16^3 times 32 lattice with a lattice spacing of about 0.10 fm generated with the non-perturbatively improved clover action. It is shown that several features of the energies and radial distributions are in qualitative agreement with what one expects from a simple one-body Dirac equation interpretation.

   hep-latPoS(2006)·7 citations
3. 03*

   Field Theory Simulations on a Fuzzy Sphere - an Alternative to the Lattice

   Julieta Medina🇲🇽 · Wolfgang Bietenholz🇩🇪 · Frank Hofheinz🇩🇪 · Denjoe O'Connor🇮🇪

   We explore a new way to simulate quantum field theory, without introducing a spatial lattice. As a pilot study we apply this method to the 3d \lambda \phi^4 model. The regularisation consists of a fuzzy sphere with radius R for the two spatial directions, plus a discrete Euclidean time. The fuzzy sphere approximates the algebra of functions of the sphere with a matrix algebra, and the scalar field is represented by a Hermitian N x N matrix at each time site. We evaluate the phase diagram, where we find a disordered phase and an ordered regime, which splits into phases of uniform and non-uniform order. We discuss the behaviour of the model in different limits of large N and R, which lead to a commutative or to a non-commutative \lambda \phi^4 model in flat space.

   hep-lathep-thPoS(2006)·19 citations
4. 04*

   Renormalization-group blocking the fourth root of the staggered determinant

   Yigal Shamir🇮🇱

   Lattice QCD simulations with staggered fermions rely on the ``fourth-root trick.'' The validity of this trick has been proved for free staggered fermions using renormalization-group block transformations. I review the elements of the construction and discuss how it might be generalized to the interacting case.

   hep-latPoS(2006)·3 citations
5. 05*

   Localization properties of the topological charge density and the low lying eigenmodes of overlap fermions

   Y. Koma🇩🇪 · E.-M. Ilgenfritz🇩🇪 · K. Koller🇩🇪 · G. Schierholz🇩🇪 · T. Streuer🇩🇪 · V. Weinberg🇩🇪

   Overlap fermions, which preserve exact chiral symmetry on the lattice, provide a powerful tool for investigating the topological structure of the vacuum. Applying this formulation to zero-temperature quenched SU(3) configurations generated by means of the Luescher-Weisz action, we define the topological charge density with and without UV filtering and study its properties by looking at the density profile and the two-point correlation function. We observe that the density possesses global sign coherent structures, which get increasingly tangled as more and more modes are included. This change of the structure is also detected by the increasing negative tail of the two-point function. We also study the inverse participation ratio of the eigenmodes and discuss their dimensionality.

   hep-latPoS(2006)·30 citations
6. 06*

   B_s-\bar{B_s} mixing with a chiral light quark action

   D. Becirevic🇫🇷 · B. Blossier🇫🇷 · Ph. Boucaud🇫🇷 · J.P. Leroy🇫🇷 · A. Le Yaouanc🇫🇷 · O. Pene🇫🇷

   We study the $B_s^0-\overline{B_s^0}$ mixing amplitude in Standard Model by computing the relevant hadronic matrix element in the static limit of lattice HQET with the Neuberger light quark action. In the quenched approximation, and after matching to the $\overline{\mathrm{MS}}$ scheme in QCD, we obtain $B_{B_s}^{\overline{\mathrm{MS}}}(m_b)=0.940(16)(22)$.

   hep-latPoS(2006)·5 citations
7. 07*

   Real-time dynamics of proton decay

   Dmitri Grigoriev🇮🇪

   Substituting Skyrmion for nucleon, one can potentially see -- in real time -- how the monopole is catalysing the proton (or neutron) decay, and even obtain a plausible estimate for catalysis cross-section. Here we discuss the key aspects of a practical implementation of such approach and demonstrate how one can overcome the main technical problems: Gauss constraint violation and reflections at the boundaries.

   hep-latPoS(2006)·0 citations
8. 08*

   The high density region of QCD in a large mass and chemical potential model

   Roberto De Pietri🇮🇹 · Alessandra Feo (Dip. di Fisica, Univ. di Parma)🇮🇹 · Erhard Seiler (MPI fuer Physik, Muenchen)🇩🇪 · Ion-Olimpiu Stamatescu (FEST, Heidelberg and Inst. Theor. Physik, Univ. Heidelberg)🇩🇪

   We study the high density region of QCD within an effective model obtained in the frame of the hopping parameter expansion. The model still acknowledges the sign problem peculiar to non-zero chemical potential, but it permits the development of refined algorithms which ensure a good overlap of the Monte Carlo ensemble with the true one. We review the main features of the model, including the most explicit form of the resumed expansion, and present calculations concerning the dependence of various observables on the chemical potential and on the temperature, in particular of the charge density and the diquark susceptibility, which may be used to characterize the various phases expected at high baryonic density.

   hep-latPoS(2006)·4 citations
9. 09*

   Cutoff effects in maximally twisted LQCD

   Giancarlo Rossi🇮🇹 · Roberto Frezzotti🇮🇹 · Guido Martinelli🇮🇹 · Mauro Papinutto🇩🇪

   The Symanzik analysis of correlators in lattice QCD with maximally twisted Wilson fermions reveals that there exist cutoff artifacts which tend to become large as the quark mass gets small. We show that these effects can be reduced to a negligible level by either introducing the clover term in the action or, as already suggested in the literature, by a suitable choice of the critical mass. Recent simulation data support these conclusions.

   hep-latPoS(2006)·1 citation
10. 10*

    Predictions from Lattice QCD

    Andreas S. Kronfeld🇺🇸 · I.F. Allison🇬🇧 · C. Aubin🇺🇸 · C. Bernard🇺🇸 · C.T.H. Davies🇬🇧 · C. DeTar🇺🇸 · M. Di Pierro🇺🇸 · E.D. Freeland🇺🇸 · Steven Gottlieb🇺🇸 · A. Gray🇺🇸 · E. Gregory · U.M. Heller🇺🇸 and 15 other authors

    In the past year, we calculated with lattice QCD three quantities that were unknown or poorly known. They are the $q^2$ dependence of the form factor in semileptonic $D\to Kl\nu$ decay, the decay constant of the $D$ meson, and the mass of the $B_c$ meson. In this talk, we summarize these calculations, with emphasis on their (subsequent) confirmation by experiments.

    hep-lathep-exhep-phInt.J.Mod.Phys.A(2006)·19 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.