Mon·Oct 6, 2003Monday·October 6, 2003

1. 01*

   A study of colour field distributions in the baryon

   F. Okiharu (Nihon U.)🇯🇵 · R. M. Woloshyn (TRIUMF)🇨🇦

   The distributions of chromo-electric and chromo-magnetic field associated with flux tubes in the baryon are studied in SU(3) lattice QCD. Maximal Abelian projection is used to reduce the statistical fluctuations. For a fixed source geometry, many different string configurations are possible. We investigated whether the string configuration, that is the choice of operator, biases the observed flux distribution.

   hep-latNucl.Phys.B Proc.Suppl.(2004)·39 citations
2. 02*

   Heavy quark masses from finite volume effects

   Nazario Tantalo🇮🇹

   I discuss the results of a new calculation of the charm and bottom quark masses in the quenched approximation and in the continuum limit of lattice QCD. The work has been done by the APE group at the ``Tor Vergata'' University making use of the step scaling method, previously introduced to deal with two scale problems, that allows to take the continuum limit of the lattice data. We have computed the RGI quark masses and then we have connected the results to the MSbar scheme. The continuum numbers are m_b^{RGI} = 6.73(16) GeV for the b-quark and m_c^{RGI} = 1.681(36) GeV for the c-quark, corresponding respectively to m_b^{MSbar}(m_b^{MSbar}) = 4.33(10) GeV and m_c^{MSbar}(m_c^{MSbar}) = 1.319(28) GeV. The latter result, in agreement with current estimates, is for us a check of the method.

   hep-latNucl.Phys.B Proc.Suppl.(2004)·1 citation
3. 03*

   Heavy-light decay constants from the step scaling method

   Filippo Palombi🇮🇹

   We discuss results for the heavy-light decay constants in the continuum limit of quenched lattice QCD from finite size scaling techniques. We disentangle the simultaneous presence of the different energy scales characterizing heavy-light physics by first performing simulations at the unphysical volume L_0=0.4 fm, and then evolving the results towards the infinite volume. We find f_{Bs}= 192(6)(4) MeV and f_{Ds}=240(5)(5) MeV. The approach has been developed by the APE group at the University of Rome ``Tor Vergata''.

   hep-latNucl.Phys.B Proc.Suppl.(2004)·1 citation
4. 04*

   Hadronic transitions from the lattice

   Chris Michael🇬🇧

   I discuss strategies to determine hadronic decay couplings from lattice studies. As a check of the methods, I explore the decay of a vector meson to two pseudoscalar mesons with $N_f=2$ flavours of sea quark. Although we are working with quark masses that do not allow a physical decay, I show how the transition rate can be evaluated from the amplitude for $\rho \to \pi \pi$ and from the annihilation component of $\pi \pi \to \pi \pi$. I explore the decay amplitude for two different pion momenta and find consistent results. The coupling strength found is in agreement with experiment. I also find evidence for a shift in the $\rho$ mass caused by mixing with two pion states. I also present results for the decay of a hybrid meson, for the case of heavy valence quarks.

   hep-latNucl.Phys.B Proc.Suppl.(2004)·2 citations
5. 05*

   Dynamics of Monopoles and Flux Tubes in Two-Flavor Dynamical QCD

   V.G. Bornyakov🇷🇺 · H. Ichie🇯🇵 · Y. Koma🇩🇪 · Y. Mori🇯🇵 · Y. Nakamura🇯🇵 · D. Pleiter🇩🇪 · M.I. Polikarpov🇷🇺 · G. Schierholz🇩🇪 · T. Streuer🇩🇪 · H. Stüben🇩🇪 · T. Suzuki🇯🇵

   We investigate the confining properties of the QCD vacuum with $N_f=2$ flavors of dynamical quarks, and compare the results with the properties of the quenched theory. We use non-perturbatively $\mathcal{O}(a)$ improved Wilson fermions to keep cut-off effects small. We focus on color magnetic monopoles. Among the quantities we study are the monopole density and the monopole screening length, the static potential and the profile of the color electric flux tube. We furthermore derive the low-energy effective monopole action. Marked differences between the quenched and dynamical vacuum are found.

   hep-lathep-thPRD(2004)·53 citations
6. 06*

   Unphysical Operators in Partially Quenched QCD

   Stephen R. Sharpe🇺🇸 · Ruth S. Van de Water🇺🇸

   We point out that the chiral Lagrangian describing pseudo-Goldstone bosons in partially quenched QCD has one more four-derivative operator than that for unquenched QCD with three flavors. The new operator can be chosen to vanish in the unquenched sector of the partially quenched theory. Its contributions begin at next-to-leading order in the chiral expansion. At this order it contributes only to unphysical scattering processes, and we work out some examples. Its contributions to pseudo-Goldstone properties begin at next-to-next-to-leading order, and we determine their form. We also determine all the zero and two derivative operators in the $O(p^6)$ partially quenched chiral Lagrangian, finding three more than in unquenched QCD, and use these to give the general form of the analytic next-to-next-to-leading order contributions to the pseudo-Goldstone mass and decay constant. We discuss the general implications of such additional operators for the utility of partially quenched simulations

   hep-latPRD(2004)·35 citations
7. 07*

   Glueball Matrix Elements on Anisotropic Lattices

   Y. Chen🇨🇳 · S.-J. Dong🇺🇸 · T. Draper🇺🇸 · I. Horvath🇺🇸 · F.-X. Lee🇺🇸 · 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 in the range 0.1fm -- 0.2fm. These matrix elements are needed to predict the glueball branching ratios in $J/\psi$ radiative decays which will help to 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 also studied. The lattice spacing dependence of our results is very small and the continuum limits are reliably extrapolated.

   hep-latNucl.Phys.B Proc.Suppl.(2004)·2 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.