Mon·Oct 3, 2005Monday·October 3, 2005

1. 01*

   Series representation; Pade' approximants and critical behavior in QCD at nonzero T and $m{u}_B$

   M.P. Lombardo🇮🇹

   We discuss the analytic continuation beyond $\mu /T\simeq 1$ in QCD at nonzero T and $\mu$ by use of the Pade' approximants. The slope of the critical line obtained in this way increases at large $\mu$ with respect to the second order Taylor result.In the hot phase Pade' and Taylor approximants coincide, suggesting a very large, and possibly infinite, radius of convergence of the Taylor series in this thermodynamic region.

   hep-latPoS(2006)·30 citations
2. 02*

   Light hadron spectroscopy in quenched QCD with overlap fermions

   Ronald Babich (1)🇺🇸 · Federico Berruto (2)🇺🇸 · Nicolas Garron (3)🇩🇪 · Christian Hoelbling (4)🇩🇪 · Joseph Howard (1)🇺🇸 · Laurent Lellouch (5)🇫🇷 · Claudio Rebbi (1)🇺🇸 · Noam Shoresh (6) ((1) Boston University, (2) BNL, (3) DESY Zeuthen, (4) Wuppertal, (5) CPT Marseille, (6) Harvard University)🇺🇸

   A simulation of quenched QCD with the overlap Dirac operator has been carried out using 100 Wilson gauge configurations at beta = 6 on an 18^3 x 64 lattice and at beta = 5.85 on a 14^3 x 48 lattice. Here we present results for meson masses, meson final state "wave functions," decay constants, and other observables, as well as details on our algorithmic and data analysis techniques. We also summarize results for baryon masses and quark and diquark propagators in the Landau gauge.

   hep-latPoS(2006)·4 citations
3. 03*

   QED_3 on a space-time lattice: a comparison between compact and noncompact formulation

   Roberto Fiore🇮🇹 · Pietro Giudice🇮🇹 · Domenico Giuliano🇮🇹 · Donatella Marmottini🇮🇹 · Alessandro Papa🇮🇹 · Pasquale Sodano🇮🇹

   Quantum electrodynamics in a (2+1)-dimensional space-time has been object of studies both as effective theory for the pseudogap phase of high-T_c superconductors and for the theoretical investigation of mechanisms of confinement in presence of matter fields. We discretize the theory using both compact and noncompact formulations, analyze the behavior of the chiral condensate and of the monopole density and compare them. Finally we draw some conclusions about the possible equivalence of the two lattice formulations.

   hep-latPoS(2006)·2 citations
4. 04*

   Parameter dependence of the topology change and the scaling properties of the topology conserving gauge action

   H. Fukaya🇯🇵 · T. Onogi (YITP, Kyoto U.)🇯🇵 · S. Hashimoto (KEK/Sokendai)🇯🇵 · T. Hirohashi (Kyoto U.)🇯🇵 · K. Ogawa (Sokendai)🇯🇵

   The topology conserving gauge action proposed by Luescher is expected to reduce the number of non-smooth gauge configurations as well as the topology change compared to the conventional actions for the same lattice spacings. We report our quenched QCD study of the topological stability and the scaling violation of the static quark potential. We find that the the topology change is indeed suppressed when the parameter epsilon is of order one. We also find that the scaling violation in the static quark potential remain reasonably small in the parameter range of our study. Our study is done at the inverse lattice spacing a^{-1}=1.4-2.5 GeV with the lattice size L=1.0-1.6fm.

   hep-latPoS(2006)·2 citations
5. 05*

   Hadron structure with light dynamical quarks

   LHPC Collaboration: Robert G. Edwards (1)🇺🇸 · George Taminga Fleming (2)🇺🇸 · Philipp Hagler (3)🇳🇱 · John W. Negele (4)🇺🇸 · Kostas Orginos (4)🇺🇸 · Andrew V. Pochinsky (4)🇺🇸 · Dru B. Renner (5)🇺🇸 · David G. Richards (1)🇺🇸 · Wolfram Schroers (6) ((1) JLAB, (2) Yale University, (3) Vrije Universiteit Amsterdam, (4) MIT, (5) Arizona University, (6) NIC Zeuthen)🇩🇪

   Generalized parton distributions encompass a wealth of information concerning the three-dimensional quark and gluon structure of the nucleon, and thus provide an ideal focus for the study of hadron structure using lattice QCD. The special limits corresponding to form factors and parton distributions are well explored experimentally, providing clear tests of lattice calculations, and the lack of experimental data for more general cases provides opportunities for genuine predictions and for guiding experiment. We present results from hybrid calculations with improved staggered (Asqtad) sea quarks and domain wall valence quarks at pion masses down to 350 MeV.

   hep-latPoS(2006)·61 citations
6. 06*

   The pressure and a possible hidden Hagedorn transition at large-N

   Barak Bringoltz🇬🇧 · Michael Teper (Oxford U., Theor. Phys.)🇬🇧

   In the first part of this contribution we present a numerical study motivated by recent attempts to understand the nonperturbative aspects of QCD at temperatures T~ a few times the deconfinement temperature Tc. We focus on the pure gauge theory, and ask whether the deficit in pressure and entropy, with respect to their free-gas values, is particular to SU(3). We find that the deficit in SU(4),SU(8) for T>= 2Tc,1.6 Tc, respectively, is remarkably close to that of SU(3). This suggests a similar deficit for SU(oo), which is fortunate since this theory is simpler, and can serve to constrain the possible dynamics underlying the deficits. In the second part we seek for signs of a Hagedorn temperature T_H in pure lattice SU(N) gauge theories with N=8,10,12. Since one expects T_H>Tc, we measure masses of strings in the metastable confined phase above Tc, and extrapolatethem to zero to estimate T_H. For SU(12) we find that T_H/Tc=1.116(9), when we extrapolate with a critical exponentof the three dimensional XY model, which seems to be preferred over a mean field exponent by our data.

   hep-latPoS(2006)·3 citations
7. 07*

   Applying Groebner Bases to Solve Reduction Problems for Feynman Integrals

   A.V. Smirnov🇷🇺 · V.A. Smirnov🇷🇺

   We describe how Groebner bases can be used to solve the reduction problem for Feynman integrals, i.e. to construct an algorithm that provides the possibility to express a Feynman integral of a given family as a linear combination of some master integrals. Our approach is based on a generalized Buchberger algorithm for constructing Groebner-type bases associated with polynomials of shift operators. We illustrate it through various examples of reduction problems for families of one- and two-loop Feynman integrals. We also solve the reduction problem for a family of integrals contributing to the three-loop static quark potential.

   hep-lathep-phhep-thmath-ph+1JHEP(2006)·75 citations
8. 08*

   Dynamical determination of B_K from improved staggered quarks

   E. Gamiz🇬🇧 · S. Collins🇬🇧 · C. T. H. Davies🇬🇧 · J. Shigemitsu🇺🇸 · M. Wingate (HPQCD and UKQCD collaborations)🇺🇸

   The scaling corrections that affected previous staggered calculations of B_K have been proved to be reduced by using improved actions (HYP, Asqtad) in the quenched approximation. This improved behaviour allows us to perform a reliable dynamical calculation of B_K including quark vacuum polarization effects using the MILC (2+1) flavour dynamical configurations. We report here on the results from such dynamical calculation. We also discuss the renormalization effects with the Asqtad action.

   hep-latPoS(2006)·5 citations
9. 09*

   Low-energy J/psi-Hadron Interactions from Quenched Lattice QCD

   K. Yokokawa🇯🇵 · S. Sasaki🇺🇸 · A. Hayashigaki🇩🇪 · T. Hatsuda🇯🇵

   The J/psi-hadron interaction is a key ingredient in analyzing the J/psi suppression in hot hadronic matter as well as the propagation of J/psi in nuclei. As a first step to clarify the J/psi-hadron interactions at low energies, we have calculated J/psi-pi, J/psi-rho and J/psi-nucleon scattering lengths by the quenched lattice QCD simulations with Wilson fermions for beta=6.2 on 24^3*48 and 32^3*48 lattices. Using the Luscher's method to extract the scattering length from the simulations in a finite box, we find an attractive interaction in the S-wave channel for all three systems: Among others, the J/psi-nucleon interaction is most attractive. Possibility of the J/psi-nucleon bound state is also discussed.

   hep-lathep-phnucl-thPoS(2006)·2 citations
10. 10*

    Double poles in Lattice QCD with mixed actions

    Maarten Golterman (SFSU)🇺🇸 · Taku Izubuchi (RIKEN-BNL and Kanazawa)🇺🇸 · Yigal Shamir (Tel-Aviv)🇮🇱

    We consider effects resulting from the use of different discretizations for the valence and the sea quarks, considering Wilson and/or Ginsparg--Wilson fermions. We assume that such effects appear through scaling violations that can be studied using effective-lagrangian techniques. We show that a double pole is present in flavor-neutral Goldstone meson propagators, even if the flavor non-diagonal Goldstone mesons made out of valence or sea quark have equal masses. We then consider some observables known to be anomalously sensitive to the presence of a double pole. We find that the double-pole enhanced scaling violations may turn out to be rather small in practice.

    hep-latPoS(2006)·1 citation
11. 11*

    Dimensional regularization of Schrodinger Functional correlation functions

    Eduardo Obeso (Madrid, Autonoma U.)🇪🇸

    The matching between Schrodinger Functional renormalization schemes and conventional perturbative schemes is usually done using an intermediate lattice scheme. We propose to do the matching directly. This requires the perturbative evaluation of Schrodinger Functional correlation functions in the continuum. We use dimensional regularization but due to the lack of translational invariance in the Euclidean time direction, we employ a general technique introduced by Luscher. In this talk I describe this technique and its application to the one-loop expansion of correlation functions used in the definition of the renormalized quark mass in the Schrodinger Functional scheme. The divergent parts are identified and the computation of finite parts is in progress.

    hep-latPoS(2006)·1 citation
12. 12*

    Critical Behaviour in Statistical QCD

    Helmut Satz🇩🇪

    We survey the critical behaviour of strongly interacting matter, as determined in finite temperature lattice QCD.

    hep-latInt.J.Mod.Phys.A(2006)·16 citations
13. 13*

    Pseudoscalar singlet physics with staggered fermions

    Eric B. Gregory🇬🇧 · Alan C. Irving🇬🇧 · Craig McNeile🇬🇧 · Steven Miller🇬🇧 · Zbigniew Sroczynski🇬🇧

    We report on progress in measuring disconnected correlators associated with pseudoscalar flavor-singlet mesons. This will eventually allow us to compute the masses of the eta and eta' mesons. Flavor-singlet physics also presents an interesting test of the staggered fermion formulation, as disconnected correlators are sensitive to whether the same action governs both sea quarks and valence quarks. It can also help test the validity of the ``fourth-root trick'' used in unquenched lattice calculations where the number of flavors $N_f<4$.

    hep-latPoS(2006)·5 citations
14. 14*

    Scaling test of quenched Wilson twisted mass QCD at maximal twist

    K. Jansen🇩🇪 · M. Papinutto🇩🇪 · A. Shindler🇩🇪 · C. Urbach🇩🇪 · I. Wetzorke🇩🇪

    We present the results of an extended scaling test of quenched Wilson twisted mass QCD. We fix the twist angle by using two definitions of the critical mass, the first obtained by requiring the vanishing of the pseudoscalar meson mass m_PS for standard Wilson fermions and the second by requiring restoration of parity at non-zero value of the twisted mass mu and subsequently extrapolating to mu=0. Depending on the choice of the critical mass we simulate at values of beta in [5.7,6.45], for a range of pseudoscalar meson masses 250 MeV < m_PS < 1 GeV and we perform the continuum limit for the pseudoscalar meson decay constant f_PS and various hadron masses (vector meson m_V, baryon octet m_oct and baryon decuplet m_dec) at fixed value of r_0 m_PS. For both definitions of the critical mass, lattice artifacts are consistent with O(a) improvement. However, with the second definition, large O(a^2) discretization errors present at small quark mass with the first definition are strongly suppressed. The results in the continuum limit are in very good agreement with those from the Alpha and CP-PACS Collaborations.

    hep-latPoS(2006)·1 citation
15. 15*

    The Kaon B-Parameter in Staggered Chiral Perturbation Theory

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

    We calculate the kaon B-parameter, B_K, to next-to-leading order in staggered chiral perturbation theory. We extend the usual power counting to include the effects of using perturbative (rather than non-perturbative) matching factors. Taste breaking enters through the O(a^2) terms in the effective action, through mixing with higher-dimension operators, and through the truncation of matching factors. These effects cause mixing with several additional operators, complicating the chiral and continuum extrapolations. We summarize the results here; all details can be found in hep-lat/0507012.

    hep-latPoS(2006)·4 citations
16. 16*

    Meson decay constants from Nf=2 clover fermions

    M. Göckeler🇩🇪 · R. Horsley🇬🇧 · D. Pleiter🇩🇪 · P. E. L. Rakow🇬🇧 · G. Schierholz🇩🇪 · W. Schroers🇩🇪 · H. Stüben🇩🇪 · J. M. Zanotti🇩🇪

    We present recent results for meson decay constants calculated on configurations with two flavours of O(a)-improved Wilson fermions. Non-perturbative renormalisation is applied and quark mass dependencies as well as finite volume and discretisation effects are investigated. In this work we also present a computation of the coupling of the light vector mesons to the tensor current using dynamical fermions.

    hep-latPoS(2006)·16 citations
17. 17*

    NRQCD results on the MILC extra coarse ensemble

    I. F. Allison🇬🇧 · C.T.H. Davies🇬🇧 · A. Gray🇺🇸

    We present preliminary results using NRQCD to describe heavy quarks on the MILC 2+1 flavour dynamical extra coarse ensemble. We calculate the spectra of low lying states in bottomonium to complement earlier results on the finer MILC ensembles. We then exploit the coarseness of the lattices to calculate charm propagators using NRQCD. These are used to examine the charmonium spectrum and to calclate the mass of the $B_c$ using NRQCD. Finally we look breifly at the $B_d$ and $B_s$ systems using the imporoved staggered formalism to describe the light valence quarks.

    hep-latPoS(2006)·0 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.