Thu·Oct 25, 2007Thursday·October 25, 2007

1. 01*

   Bulk thermodynamics and charge fluctuations at non-vanishing baryon density

   Chuan Miao🇩🇪 · Christian Schmidt🇩🇪

   We present results on bulk thermodynamic quantities as well as net baryon number, strangeness and electric charge fluctuations in QCD at non-zero density and temperature obtained from lattice calculations with almost physical quark masses for two values of the lattice cut-off $aT=1/4$ and 1/6 . We show that with our improved p4fa3-action the cut-off effects are under control when using lattices with a temporal extent of 6 or larger and that the contribution to the equation of state, which is due to a finite chemical potential is small for ${\mu }_q/T<1$. Moreover, at vanishing chemical potential, i.e. under conditions almost realized at RHIC and the LHC, quartic fluctuations of net baryon number and strangeness are large in a narrow temperature interval characterizing the transition region from the low to high temperature phase. At non-zero baryon number density, strangeness fluctuations are enhanced and correlated to fluctuations of the net baryon number. If strangeness is furthermore forced to vanish, as it may be the case in systems created in heavy ion collisions, strangeness fluctuations are significantly smaller than baryon number fluctuations.

   hep-latPoS(2007)·10 citations
2. 02*

   Heavy-Quark Masses from the Fermilab Method in Three-Flavor Lattice QCD

   Elizabeth D. Freeland · Andreas S. Kronfeld · James N. Simone · Ruth S. Van de Water · Fermilab Lattice · MILC Collaborations

   We report on heavy quark mass calculations using Fermilab heavy quarks. Lattice calculations of heavy-strange meson masses are combined with one-loop (automated) lattice perturbation theory to arrive at the quark mass. Mesons are constructed from Fermilab heavy quarks and staggered light quarks. We use the MILC ensembles at three lattice spacings and sea quark mass ratios of $m_{\mathrm{u},\mathrm{d}}/m_{\mathrm{s}}=0.1$ to 0.4. Preliminary results for the bottom quark are given in the potential subtracted scheme.

   hep-latPoS(2007)·5 citations
3. 03*

   Charm Quarks and the QCD Equation of State

   Michael Cheng (for the RBC-Bielefeld Collaboration)🇺🇸

   We present a study of the effect of charm quarks on the QCD equation of state using partially-quenched p4 charm quarks on a dynamically generated 2+1 flavor background, at zero chemical potential. We show preliminary results for the charm quark contribution to the energy density and pressure in the high temperature region ($T_c<T<4T_c$) and compare it to the free-field calculation. The charm quark mass is determined by measuring the charmonium spectrum.

   hep-latPoS(2007)·31 citations
4. 04*

   Lattice QCD approach to nuclear force

   N.Ishii (Tsukuba U., CCS)🇯🇵 · S.Aoki (Tsukuba U., GSPAS)🇯🇵 · T.Hatsuda (Tokyo U.)🇯🇵

   We present our updated results of the nucleon-nucleon potential in quenched lattice QCD simulations with the plaquette gauge action and the Wilson quark action on the 32^4(\simeq (4.4 fm)^4) lattice. From the equal-time Bethe-Salpeter (BS) wave function, the NN potential is constructed through the Schroedinger-type equation. Resulting NN potential has all the qualitative features which phenomenological potentials commonly have: the repulsive core at short distance and the attractive well at medium and long distances. In the L \to \infty limit, our NN potential is guaranteed to reproduce the scattering length obtained from the Luescher's formula. The quark mass dependence of the NN potential is studied with m_{pi} \sim 380, 529, 731 MeV. The results suggest that both the repulsive core at short distance and the attractive well at medium distance are enhanced in the light quark mass region.

   hep-latPoS(2007)·10 citations
5. 05*

   Transverse momentum distributions of quarks from the lattice using extended gauge links

   Bernhard U. Musch (1) · Philipp Hägler (1) · Andreas Schäfer (2) · Meinulf Göckeler (2) · Dru B. Renner (3) · John W. Negele (4) · LHPC Collaboration ((1) Technische Universität München, (2) Universität Regensburg, (3) University of Arizona, (4) Massachusetts Institute of Technology)

   We present preliminary numerical studies in Lattice QCD related to the intrinsic transverse momentum distribution of partons in the nucleon. We employ non-local operators, consisting of spatially separated quark creation and annihilation operators connected by a straight Wilson line. A clear signal is already obtained from a small number of configurations at a pion mass of about 600 MeV. As an example, we demonstrate that we can obtain the first x-moment of the transverse momentum dependent parton distribution function f_1^{n=1}(k_T) from our data. Our results, which are not renormalized, show a Gaussian-like distribution. The root mean squared transverse momentum is about 560 MeV for a Gaussian fit, close to phenomenological values.

   hep-latPoS(2007)·20 citations
6. 06*

   Hadron spectrum of QCD with one quark flavor

   F. Farchioni🇩🇪 · I. Montvay🇩🇪 · G. Munster🇩🇪 · E.E. Scholz🇺🇸 · T. Sudmann🇩🇪 · J. Wuilloud🇩🇪

   The hadron spectrum of one flavor QCD is studied by Monte Carlo simulations. The Symanzik tree-level-improved Wilson action is used for the gauge field and the Wilson action for the fermion. The theory is simulated by a polynomial hybrid Monte Carlo algorithm (PHMC). The mass spectrum of hadronic bound states is investigated at two different lattice spacings: a ~ 0.37r_0 and a ~ 0.27r_0, corresponding to ~0.19fm and ~0.13fm in ordinary QCD. The lattice extension is fixed to L ~ 4.4r_0 (~2.2fm). The lightest simulated quark mass corresponds to a pion with mass ~270MeV. Properties of the theory are analyzed by making use of the ideas of partially quenched chiral perturbation theory (PQChPT). The symmetry of the single flavor theory can be artificially enhanced by adding extra valence quarks, which can be interpreted as u and d quarks. Operators in the valence pion sector can be built. Masses and decay constants are analyzed by using PQChPT formulae at next-to-leading order.

   hep-latPoS(2006)·4 citations
7. 07*

   Theta vacuum physics from QCD at fixed topology

   Sinya Aoki🇯🇵 · Hidenori Fukaya🇯🇵 · Shoji Hashimoto🇯🇵 · Tetsuya Onogi🇯🇵

   We propose a method to obtain physical quantities in the theta vacuum from those at fixed topology, which are different by finite size effects. Extending the work by Brower et al., we derive the formula to estimate these finite size corrections for arbitrary correlators in terms of the topological susceptibility and the theta dependence. Applying this formula, we show that topological susceptibility can be measured through two-point functions of pseudoscalar operator.

   hep-latPoS(2007)·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.