Thu·Sep 22, 2005Thursday·September 22, 2005

1. 01*

   Magnetic polarizability of hadrons from lattice QCD in the background field method

   F.X. Lee🇺🇸 · L. Zhou🇺🇸 · W. Wilcox🇺🇸 · J. Christensen🇺🇸

   We present a calculation of hadron magnetic polarizability using the techniques of lattice QCD. This is carried out by introducing a uniform external magnetic field on the lattice and measuring the quadratic part of a hadron's mass shift. The calculation is performed on a $24^4$ lattice with standard Wilson actions at beta=6.0 (spacing $a=0.1$ fm) and pion mass down to about 500 MeV. Results are obtained for 30 particles covering the entire baryon octet ($n$, $p$, ${\Sigma }^0$, ${\Sigma }^{-}$, ${\Sigma }^{+}$, ${\Xi }^{-}$, ${\Xi }^0$, $\Lambda$) and decuplet (${\Delta }^0$, ${\Delta }^{-}$, ${\Delta }^{+}$, ${\Delta }^{++}$, ${\Sigma }^{\ast 0}$, ${\Sigma }^{\ast -}$, ${\Sigma }^{\ast +}$, ${\Xi }^{\ast 0}$, ${\Xi }^{\ast -}$, ${\Omega }^{-}$), plus selected mesons (${\pi }^0$, ${\pi }^{+}$, ${\pi }^{-}$, $K^0$, $K^{+}$, $K^{-}$, ${\rho }^0$, ${\rho }^{+}$, ${\rho }^{-}$, $K^{\ast 0}$, $K^{\ast +}$, $K^{\ast -}$). The results are compared with available values from experiments and other theoretical calculations.

   hep-lathep-exhep-phnucl-ex+1PRD(2006)·81 citations
2. 02*

   Coherent Topological Charge Structure in $C{P}^{N-1}$ Models and QCD

   Saeed Ahmad🇺🇸 · Jonathan T. Lenaghan🇺🇸 · H. B. Thacker🇺🇸

   In an effort to clarify the significance of the recent observation of long-range topological charge coherence in QCD gauge configurations, we study the local topological charge distributions in two-dimensional $C{P}^{N-1}$ sigma models, using the overlap Dirac operator to construct the lattice topological charge. We find long-range sign coherence of topological charge along extended one-dimensional structures in two-dimensional spacetime. We discuss the connection between the long range topological structure found in $C{P}^{N-1}$ and the observed sign coherence along three-dimensional sheets in four-dimensional QCD gauge configurations. In both cases, coherent regions of topological charge form along membrane-like surfaces of codimension one. We show that the Monte Carlo results, for both two-dimensional and four-dimensional gauge theory, support a view of topological charge fluctuations suggested by Luscher and Witten. In this framework, the observed membranes are associated with boundaries between ``k-vacua,'' characterized by an effective local value of $\theta$ which jumps by $\pm 2\pi$ across the boundary.

   hep-lathep-thPRD(2005)·44 citations
3. 03*

   Baryon magnetic moments in the background field method

   F.X. Lee🇺🇸 · R. Kelly🇺🇸 · L. Zhou🇺🇸 · W. Wilcox🇺🇸

   We present a calculation of the magnetic moments for the baryon octet and decuplet using the background-field method and standard Wilson gauge and fermion actions in the quenched approximation of lattice QCD. Progressively smaller static magnetic fields are introduced on a $24^4$ lattice at beta=6.0 and the pion mass is probed down to about 500 MeV. Magnetic moments are extracted from the linear response of the masses to the background field.

   hep-lathep-phnucl-thPLB(2005)·97 citations
4. 04*

   QCD Phases in Lattice QCD

   Sinya Aoki🇯🇵

   I review the recent status of lattice QCD calculations at non-zero density.

   hep-latInt.J.Mod.Phys.A(2006)·12 citations
5. 05*

   Lattice construction of Cho-Faddeev-Niemi decomposition and gauge invariant monopole

   S. Kato🇯🇵 · K.-I. Kondo🇯🇵 · T. Murakami🇯🇵 · A. Shibata🇯🇵 · T. Shinohara🇯🇵 · S. Ito🇯🇵

   We present the first implementation of the Cho--Faddeev--Niemi decomposition of the SU(2) Yang-Mills field on a lattice. Our construction retains the color symmetry (global SU(2) gauge invariance) even after a new type of Maximally Abelian gauge, as explicitly demonstrated by numerical simulations. Moreover, we propose a gauge-invariant definition of the magnetic monopole current using this formulation and compare the new definition with the conventional one by DeGrand and Toussaint to exhibit its validity.

   hep-lathep-phPLB(2006)·71 citations
6. 06*

   Localized eigenmodes of the covariant lattice Laplacian

   J. Greensite🇺🇸 · S. Olejnik🇸🇰 · M.I. Polikarpov🇷🇺 · S.N. Syritsyn🇷🇺 · V.I. Zakharov🇩🇪

   We study numerically the eigenmode spectrum of the covariant lattice Laplacian, in the fundamental SU(2) color group representation. It is found that eigenmodes at the lower and upper ends of the spectrum are localized, and that the localization volume scales. In contrast, the eigenmodes of the lattice Faddeev-Popov operator are all extended rather than localized (as required for confinement) despite the similarity of the kinetic and Faddeev-Popov operators.

   hep-lathep-phhep-thPoS(2006)·3 citations
7. 07*

   Gauge theories on a five-dimensional orbifold

   Francesco Knechtli🇩🇪 · Burkhard Bunk🇩🇪 · Nikos Irges🇬🇷

   We present a construction of non-Abelian gauge theories on the R^4 x S^1/Z_2 orbifold. We show that no divergent boundary mass term for the Higgs field, identified with some of the fifth dimensional components of the gauge field, is generated. The formulation of the theories on the lattice requires only Dirichlet boundary conditions that specify the breaking of the gauge group. The first simulations in order to resolve the issue whether these theories can be used at low energy as weakly interacting effective theories have been performed. In case of a positive answer, these theories could provide us with a new framework for studying electroweak symmetry breaking.

   hep-lathep-phPoS(2006)·11 citations
8. 08*

   Perturbative renormalisation of quark bilinear operators for overlap fermions with and without stout links and improved gauge action

   R. Horsley (Edinburgh)🇬🇧 · H. Perlt (Regensburg, Leipzig)🇩🇪 · P.E.L. Rakow (Liverpool)🇬🇧 · G. Schierholz (DESY)🇩🇪 · A. Schiller (Leipzig)🇩🇪

   We calculate lattice renormalisation constants of local and one-link quark operators for overlap fermions and improved gauge actions in one-loop perturbation theory. For the local operators we stout smear the SU(3) links in the fermionic action. Using the popular tadpole improved Lüscher-Weisz actions at $\beta =8.45$ and $\beta =8.0$ we present numerical values for the Z factors in the $\overline{MS}$ scheme (partly as function of the stout smearing strength). We compare various levels of mean field (tadpole) improvement which have been applied to our results.

   hep-latPoS(2006)·1 citation
9. 09*

   Towards a non-perturbative computation of the RGI strange quark mass with two dynamical flavors

   Michele Della Morte🇩🇪 · Roland Hoffmann🇩🇪 · Francesco Knechtli🇩🇪 · Juri Rolf🇩🇪 · Rainer Sommer🇩🇪 · Ines Wetzorke🇩🇪 · Ulli Wolff🇩🇪

   The non-perturbative running of the quark mass in the Schroedinger functional scheme is computed over a large energy range (covering scales differing by two orders of magnitude). This allows to relate lattice estimates of the running quark mass to the renormalization group invariant mass. The result is used in a preliminary computation of the strange quark mass in the theory with two flavors of non-perturbatively improved Wilson quarks. A more detailed discussion of the calculation can be found in [1].

   hep-latPoS(2006)·5 citations
10. 10*

    Large N reduction on a twisted torus

    A. Gonzalez-Arroyo (UAM)🇪🇸 · R. Narayanan (FIU)🇺🇸 · H. Neuberger (Rutgers)🇺🇸

    We consider SU(N) lattice gauge theory at infinite N defined on a torus with a CP invariant twist. Massless fermions are incorporated in an elegant way, while keeping them quenched. We present some numerical results which suggest that twisting can make numerical simulations of planar QCD more efficient.

    hep-latPLB(2005)·14 citations
11. 11*

    Lattice calculation of SU(3) flavor breaking ratios in B - anti-B mixing

    Valeriya Gadiyak🇺🇸 · Oleg Loktik🇺🇸

    We present an unquenched lattice calculation for the SU(3) flavor breaking ratios of the heavy-light decay constants and the $\Delta B=2$ matrix elements. The calculation was performed on $16^3\times 32$ lattices with two dynamical flavors of domain-wall quarks and inverse lattice spacing $1/a=1.69(5)$ GeV. Heavy quarks were implemented using an improved lattice formulation of the static approximation. In the infinite heavy-quark mass limit we obtain $f_{B_s}/f_{B_d}=1.29(4)(6)$, $B_{B_s}/B_{B_d}=1.06(6)(4)$, $\xi =1.33(8)(8)$ where the first error is statistical and the second systematic.

    hep-latPRD(2005)·14 citations
12. 12*

    Probing Unquenching Effects in the Gluon Polarisation in Light Mesons

    C. S. Fischer🇬🇧 · P. Watson🇩🇪 · W. Cassing🇩🇪

    We introduce an extension to the ladder truncated Bethe-Salpeter equation for mesons and the rainbow truncated quark Dyson-Schwinger equations which includes quark-loop corrections to the gluon propagator. This truncation scheme obeys the axialvector Ward-Takahashi identity relating the quark self-energy and the Bethe-Salpeter kernel. Two different approximations to the Yang-Mills sector are used as input: the first is a sophisticated truncation of the full Yang-Mills Dyson-Schwinger equations, the second is a phenomenologically motivated form. We find that the spectra and decay constants of pseudoscalar and vector mesons are overall described well for either approach. Meson mass results for charge eigenstate vector and pseudoscalar meson masses are compared to lattice data. The effects of unquenching the system are small but not negligible.

    ↳ hep-phhep-latnucl-thPRD(2005)·134 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.