Fri·Oct 14, 2005Friday·October 14, 2005

1. 01*

   Onium Masses with Three Flavors of Dynamical Quarks

   Steven Gottlieb🇺🇸 · L. Levkova (Indiana U.)🇺🇸 · M. DiPierro (DePaul U.)🇺🇸 · A. El-Khadra🇺🇸 · D. Menscher (U. Illinois)🇺🇸 · A. S. Kronfeld🇺🇸 · P. B. Mackenzie🇺🇸 · J. Simone (Fermilab)🇺🇸

   We have greatly extended an earlier calculation of the charmonium spectrum on three flavor dynamical quark ensembles by using more recent ensembles generated by the MILC collaboration. The heavy quarks are treated using the Fermilab formulation. The charmonium state masses are in reasonable agreement with the observed spectrum; however, some of the spin splittings may still be too small.

   hep-latPoS(2006)·15 citations
2. 02*

   Towards a chiral gauge theory by deconstruction in AdS5

   Tanmoy Bhattacharya (1)🇺🇸 · Rajan Gupta (1)🇺🇸 · Matthew R. Martin (1)🇺🇸 · Yuri Shirman (1)🇺🇸 · Csaba Csaki (2)🇺🇸 · John Terning (3) ((1) Los Alamos National Laboratory, (2) Cornell University, (3) University of California, Davis)🇺🇸

   We describe an implementation of a deconstructed gauge theory with charged fermions defined on an interval in five dimensional AdS space. The four dimensional slices are Minkowski, and the end slices support four dimensional chiral zero modes. In such a theory, the energy scales warp down as we move along the fifth dimension. If we augment this theory with localized neutral 4-dimensional Majorana fermions on the low energy end, and implement a Higgs mechanism there, we can arrange the theory such that the lightest gauge boson mode and the chiral mode on the wall at the high energy end are parametrically lighter than all the other states in the theory. If this semiclassical construction does not run into problems at the quantum level, this may provide an explicit construction of a chiral gauge theory. Instanton effects are expected to make the gauge boson heavy only if the resulting effective theory is anomalous.

   hep-latPoS(2006)·2 citations
3. 03*

   Glueball Spectrum and Matrix Elements on Anisotropic Lattices

   Y. Chen🇨🇳 · A. Alexandru🇺🇸 · S.J. Dong🇺🇸 · T. Draper🇺🇸 · I. Horvath🇺🇸 · F.X. Lee🇺🇸 · K.F. Liu🇺🇸 · N. Mathur🇺🇸 · C. Morningstar🇺🇸 · M. Peardon🇮🇪 · S. Tamhankar🇺🇸 · B.L. Young🇺🇸 · J.B. Zhang🇦🇺

   The glueball-to-vacuum matrix elements of local gluonic operators in scalar, tensor, and pseudoscalar channels are investigated numerically on several anisotropic lattices with the spatial lattice spacing ranging from 0.1fm - 0.2fm. These matrix elements are needed to predict the glueball branching ratios in $J/\psi$ radiative decays which will help identify the glueball states in experiments. Two types of improved local gluonic operators are constructed for a self-consistent check and the finite volume effects are studied. We find that lattice spacing dependence of our results is very weak and the continuum limits are reliably extrapolated, as a result of improvement of the lattice gauge action and local operators. We also give updated glueball masses with various quantum numbers.

   hep-lathep-phPRD(2006)·769 citations
4. 04*

   Locality and Scaling of Quenched Overlap Fermions

   Terrence Draper🇺🇸 · Nilmani Mathur🇺🇸 · Jianbo Zhang🇦🇺 · Andrei Alexandru🇺🇸 · Ying Chen🇨🇳 · Shao-Jing Dong🇺🇸 · Ivan Horvath🇺🇸 · Frank Lee🇺🇸 · Sonali Tamhankar🇺🇸

   The overlap fermion offers the tremendous advantage of exact chiral symmetry on the lattice, but is numerically intensive. This can be made affordable while still providing large lattice volumes, by using coarse lattice spacing, given that good scaling and localization properties are established. Here, using overlap fermions on quenched Iwasaki gauge configurations, we demonstrate directly that the overlap Dirac operator's range is comfortably small in lattice units for each of the lattice spacings 0.20 fm, 0.17 fm, and 0.13 fm (and scales to zero in physical units in the continuum limit). In particular, our direct results contradict recent speculation that an inverse lattice spacing of $1\mathrm{GeV}$ is too low to have satisfactory localization. Furthermore, hadronic masses (available on the two coarser lattices) scale very well.

   hep-latPoS(2006)·12 citations
5. 05*

   Two--dimensional lattice Gross--Neveu model with Wilson twisted mass fermions

   Kei-ichi Nagai🇩🇪 · Karl Jansen (NIC/DESY-Zeuthen)🇩🇪

   We study the two-dimensional lattice Gross--Neveu model with Wilson twisted mass fermions in order to explore the phase structure in this setup. In particular, we investigate the behaviour of the phase transitions found earlier with standard Wilson fermions as a function of the twisted mass parameter $\mu$. We find that qualitatively the dependence of the phase transitions on $\mu$ is very similar to the case of lattice QCD.

   hep-latPLB(2006)·5 citations
6. 06*

   The QCD phase diagram at zero and small baryon density

   Owe Philipsen (Munster U., ITP)🇩🇪

   I review recent developments in determining the QCD phase diagram by means of lattice simulations. Since the invention of methods to side-step the sign problem a few years ago, a number of additional variants have been proposed, and progress has been made towards understanding some of the systematics involved. All available techniques agree on the transition temperature as a function of density in the regime \mu_q/T < 1. There are by now four calculations with signals for a critical point, two of them at similar parameter values and with consistent results. However, it also emerges that the location of the critical point is exceedingly quark mass sensitive. At the same time sizeable finite volume, cut-off and step size effects have been uncovered, demanding additional investigations with exact algorithms on larger and finer lattices before quantitative conclusions can be drawn. Depending on the sign of these corrections, there is ample room for the eventual phase diagram to look as expected or also quite different, with no critical point at all.

   hep-latPoS(2006)·106 citations
7. 07*

   Unified chiral analysis of the vector meson spectrum from lattice QCD

   W. Armour🇬🇧 · C. R. Allton🇬🇧 · D. B. Leinweber🇦🇺 · A. W. Thomas🇺🇸 · R. D. Young🇺🇸

   The chiral extrapolation of the vector meson mass calculated in partially-quenched lattice simulations is investigated. The leading one-loop corrections to the vector meson mass are derived for partially-quenched QCD. A large sample of lattice results from the CP-PACS Collaboration is analysed, with explicit corrections for finite lattice spacing artifacts. To incorporate the effect of the opening decay channel as the chiral limit is approached, the extrapolation is studied using a necessary phenomenological extension of chiral effective field theory. This chiral analysis also provides a quantitative estimate of the leading finite volume corrections. It is found that the discretisation, finite-volume and partial quenching effects can all be very well described in this framework, producing an extrapolated value of M_\rho in excellent agreement with experiment. This procedure is also compared with extrapolations based on polynomial forms, where the results are much less enlightening.

   hep-latJ.Phys.G(2006)·34 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.