HEP Lattice·hep-lat

Tue·Oct 9, 2007Tuesday·October 9, 2007

16 papers—16 primary·0 cross-listed·reconstructed*

01*
Effects of the disconnected flavor singlet corrections on the hyperfine splitting in charmonium
C. DeTar🇺🇸 · L. Levkova🇺🇸
Experimentally the charmonium hyperfine splitting is $M_{J / ψ} - M_{η_{c}} = 117$ MeV and current lattice results are generally below this value. The difference could be due to the effects of the disconnected flavor singlet diagrams which have not been included in these calculations. Previous attempts to determine the disconnected flavor singlet corrections have led just to rough estimates in the range of $\pm 20$ MeV. We present preliminary results for these corrections calculated on fine ( $a \approx 0.09$ fm) Asqtad 2+1 flavor lattices provided by the MILC Collaboration.
hep-latPoS(2007)·6 citations
02*
QCD thermodynamics with 2+1 flavors at nonzero chemical potential
C. Bernard🇺🇸 · C. DeTar🇺🇸 · Steven Gottlieb🇺🇸 · U.M. Heller🇺🇸 · J.E. Hetrick🇺🇸 · L.Levkova · R. Sugar🇺🇸 · D. Toussaint🇺🇸
We present results for the QCD equation of state, quark densities and susceptibilities at nonzero chemical potential, using 2+1 flavor asqtad ensembles with $N_{t} = 4$ . The ensembles lie on a trajectory of constant physics for which $m_{u d} \approx 0.1 m_{s}$ . The calculation is performed using the Taylor expansion method with terms up to sixth order in $μ / T$ .
hep-latPRD(2008)·58 citations
03*
Generalized parton distributions from domain wall valence quarks and staggered sea quarks
LHPC Collaboration: D. B. Renner🇺🇸 · J. Bratt🇺🇸 · R. G. Edwards🇺🇸 · M. Engelhardt🇺🇸 · G. Fleming🇺🇸 · Ph. Hägler🇩🇪 · B. Musch🇩🇪 · J. W. Negele🇺🇸 · K. Orginos🇺🇸 · A. V. Pochinsky🇺🇸 · D. G. Richards🇺🇸 · W. Schroers🇩🇪
Moments of the generalized parton distributions of the nucleon, calculated with a mixed action of domain wall valence quarks and asqtad staggered sea quarks, are presented for pion masses extending down to 359 MeV. Results for the moments of the unpolarized, helicity, and transversity distributions are given and compared to the available experimental measurements. Additionally, a selection of the generalized form factors are shown and the implications for the spin decomposition and transverse structure of the nucleon are discussed. Particular emphasis is placed on understanding systematic errors in the lattice calculation and exploring a variety of chiral extrapolations.
hep-latPoS(2007)·11 citations
04*
Twisted mass QCD in the charm sector
B. Blossier🇩🇪 · G. Herdoiza🇮🇹 · S. Simula🇮🇹
We present preliminary results for the charm quark mass $m_{c}$ and the $D$ and $D_{s}$ mesons decay constants $f_{D}$ and $f_{D_{s}}$ from a lattice QCD calculation with $N_{f}$ = 2 dynamical fermions. We use the twisted mass fermionic action defined at maximal twist so that physical quantities are automatically $O (a)$ improved. Two lattice spacings are considered. The charm quark mass has been renormalised in the RI-MOM scheme. After a matching to the $\msb$ scheme, we obtain from the simulation at a fine lattice ( $a \sim 0.09$ fm) $m_{c}^{\msb} (m_{c}) = 1.481 \pm 0.022 \pm 0.092$ GeV, $f_{D} = 205 \pm 13 \pm 17$ MeV, $f_{D_{s}} = 271 \pm 6 \pm 6$ MeV and from the simulation at the finer lattice ( $a \sim 0.07$ fm) $m_{c}^{\msb} (m_{c}) = 1.474 \pm 0.041 \pm 0.132$ GeV, $f_{D} = 230 \pm 31 \pm 8$ MeV and $f_{D_{s}} = 264 \pm 5 \pm 8$ MeV. We chose three renormalisation conditions to determine $m_{c}$ : the spread between the final results contributes to the systematic error. At both lattice spacings, particularly at the finer one, the error on $m_{c}$ is dominated by present uncertainty on the renormalisation constant $Z_{P}$ , which should be reduced before performing a reliable continuum limit.
hep-latPoS(2007)·7 citations
05*
Charm and bottom heavy baryon mass spectrum from lattice QCD with 2+1
Heechang Na🇺🇸 · Steven Gottlieb🇺🇸
We present results for the mass spectrum of charm and bottom heavy baryons, using MILC coarse lattice configurations with 2+1 flavors. Clover heavy quark propagators with the Fermilab interpretation and improved staggered light quark propagators are used to construct two point functions with local operators for different flavor and spin states.
hep-latPoS(2007)·42 citations
06*
The gluon propagator from large asymmetric lattices
O. Oliveira🇵🇹 · P. J. Silva🇵🇹 · E.-M. Ilgenfritz🇩🇪 · A. Sternbeck🇦🇺
The Landau-gauge gluon propagator is computed for the SU(3) gauge theory on lattices up to a size of $3 2^{3} \times 200$ . We use the standard Wilson action at $β = 6.0$ and compare our results with previous computations using large asymmetric and symmetric lattices. In particular, we focus on the impact of the lattice geometry and momentum cuts to achieve compatibility between data from symmetric and asymmetric lattices for a large range of momenta.
hep-latPoS(2007)·28 citations
07*
Perturbative matching of heavy-light currents at one-loop
Aida X. El-Khadra🇺🇸 · Elvira Gámiz🇺🇸 · Andreas S. Kronfeld🇺🇸 · Matthew A. Nobes🇺🇸
We present results of a perturbative matching calculation performed at one-loop for heavy-light currents. We use the Fermilab action for the heavy quarks, the Asqtad action for the light quarks, and an improved gluon action. We also present results for heavy-heavy currents with Fermilab heavy quarks and improved glue.
hep-latPoS(2007)·18 citations
08*
Perturbing QCD with external fields
Paolo Cea🇮🇹 · Leonardo Cosmai🇮🇹 · Massimo D'Elia🇮🇹
We present some up-to-date results on QCD phase transition in a chromomagnetic constant background field and in an abelian monopole background field. Our results indicate that the QCD critical temperature is not modified by a monopole background field, whilst it is modified by a constant chromomagnetic field. We improve our earlier estimate of the QCD critical parameters in a chromomagnetic background field by performing lattice simulations with weaker fields.
hep-latPoS(2007)·2 citations
09*
Study of Hadron Scattering Using an Asymmetric Box
C. Liu🇨🇳 · Y. Shen🇨🇳 · X. Li🇺🇸 · G.Z. Meng🇨🇳 · X. Feng🇨🇳 · M. Gong🇨🇳 · S. He🇨🇳 · Y. Chen🇨🇳 · G. Li🇨🇳 · Y.B. Liu🇨🇳 · X.F. Meng🇨🇳 · J.P. Ma🇨🇳 · J.B. Zhang🇨🇳
We propose to study hadron-hadron scattering using lattice QCD in an asymmetric box which allows one to access more non-degenerate low-momentum modes for a given volume. The conventional Lüscher's formula applicable in a symmetric box is modified accordingly. To illustrate the feasibility of this approach, pion-pion elastic scattering phase shifts in the I=2, J=0 channel are calculated within quenched approximation using improved gauge and Wilson fermion actions on anisotropic lattices in an asymmetric box. After the chiral and continuum extrapolation, we find that our quenched results for the scattering phase shifts in this channel are consistent with the experimental data when the three-momentum of the pion is below 300MeV. Agreement is also found when compared with previous theoretical results from lattice and other means. Moreover, with the usage of asymmetric volume, we are able to compute the scattering phases in the low-momentum range (pion three momentum less than about 350MeV in the center of mass frame) for over a dozen values of the pion three-momenta, much more than using the conventional symmetric box with comparable volume.
hep-latPoS(2007)·2 citations
10*
Critical Behavior of CP^1 at theta = pi, Haldane's Conjecture and the Universality Class
V. Azcoiti🇪🇸 · G. Di Carlo🇮🇹 · A. Galante🇮🇹
Using an approach to analyze the theta dependence of systems with a theta-term we recently proposed, the critical behavior of CP^1 at theta=pi is studied. We find a region outside the strong coupling regime where Haldane's conjecture is verified. The critical line however does not belong to the universality class of the Wess-Zumino-Novikov-Witten model at topological coupling k=1 since it shows continuously varying critical exponents.
hep-latcond-mat.stat-mechPRL(2007)·29 citations
11*
Lattice QCD with two light Wilson quarks and maximally twisted mass
Carsten Urbach🇬🇧
We summarise status and recent results of the European Twisted Mass collaboration (ETMC). The collaboration has generated gauge configurations for three different values of the lattice spacing smaller or equal 0.1 fm and values of the charged pseudo scalar mass as low as 300 MeV with two flavours of maximally twisted mass quarks. We provide evidence that O(a) improvement works very well with maximally twisted mass fermions and that also higher order lattice artifacts appear to be small. The currently only quantity in the light meson and baryon sector where cut-off effects are visible is the neutral pseudo scalar meson mass and we present an attempt to understand this from a theoretical point of view. We describe finite size effects and quark mass dependence of the mass and decay constant of the (charged) pseudo scalar meson with chiral perturbation theory formulae and our current estimate for the low energy constants l_{3,4} is l_3=3.44(8)(35) and l_4=4.61(4)(11). Results for the average up-down, the strange and the charm quark mass and the chiral condensate are also presented.
hep-latPoS(2007)·74 citations
12*
Determination of the running coupling in pure SU(4) Yang-Mills theory
Biagio Lucini🇬🇧 · Gregory Moraitis🇬🇧
The Schrodinger functional is used to define a renormalised coupling for pure SU(4) Yang-Mills theory, with Wilson action and suitably selected boundary conditions on the link field. The coupling, which runs with the size of the lattice, is then determined by a finite-size scaling technique through a large range of momenta, thereby allowing a connection to be made between the high energy regime and the low energy non-perturbative regime, where contact is made with the physical scale of the theory. Using data from previous SU(2) and SU(3) simulations obtained with the same technique, the running of the 't Hooft coupling defined through the Schrodinger functional is studied, and we check whether the large-N expectation that g^2*N is a universal function of the energy scale E holds down to energies of the order of the string tension. Finally, we determine Lambda_SF in units of the string tension as a function of N at leading order in 1/N^2.
hep-latPoS(2007)·12 citations
13*
Moments of generalized parton distributions and quark angular momentum of the nucleon
QCDSF/UKQCD Collaboration: M. Ohtani (1)🇩🇪 · D. Brommel (1 and 2)🇩🇪 · M. Gockeler (1)🇩🇪 · Ph. Hagler (3)🇩🇪 · R. Horsley (4)🇬🇧 · Y. Nakamura (5)🇩🇪 · D. Pleiter (5)🇩🇪 · P.E.L. Rakow (6)🇬🇧 · A. Schafer (1)🇩🇪 · G. Schierholz (2 and 5)🇩🇪 · W. Schroers (5)🇩🇪 · H. Stuben (7)🇩🇪 · J.M. Zanotti (4) ((1) Regensburg U., (2) DESY, (3) Munich, Tech. U., (4) Edinburgh U., (5) NIC, Zeuthen, (6) Liverpool U., (7) Konrad Zuse Zent. Informationstech.)
The internal structure of hadrons is important for a variety of topics, including the hadron form factors, proton spin and spin asymmetry in polarized proton scattering. For a systematic study generalized parton distributions (GPDs) encode important information on hadron structure in the entire impact parameter space. We report on a computation of nucleon GPDs based on simulations with two dynamical non-perturbatively improved Wilson quarks with pion masses down to 350MeV. We present results for the total angular momentum of quarks with chiral extrapolation based on covariant baryon chiral perturbation theory.
hep-latPoS(2007)·84 citations
14*
Heavy-light decay constant at the 1/m order of HQET
Benoît Blossier🇩🇪 · Michele Della Morte🇨🇭 · Nicolas Garron🇩🇪 · Rainer Sommer🇩🇪
Following the strategy developed by the ALPHA collaboration, we present a method to compute non-perturbatively the decay constant of a heavy-light meson in HQET including the 1/m corrections. We start by a matching between HQET and QCD in a small volume to determine the parameters of the effective theory non-perturbatively. Observables in the effective theory are then evolved to larger volumes. In two steps a large enough volume is reached to determine the physical decay constant. Some preliminary results in the quenched approximation are shown.
hep-latPoS(2007)·6 citations
15*
Moments of meson distribution functions with dynamical twisted mass fermions
Rémi Baron🇫🇷 · Stefano Capitani🇩🇪 · Jaume Carbonell🇫🇷 · Karl Jansen🇩🇪 · Zhaofeng Liu🇫🇷 · Olivier Pène🇫🇷 · Carsten Urbach (for the ETM Collaboration)🇬🇧
We present our preliminary results on the lowest moment <x> of quark distribution functions of the pion using two flavor dynamical simulations with Wilson twisted mass fermions at maximal twist. The calculation is done in a range of pion masses from 300 to 500 MeV. A stochastic source method is used to reduce inversions in calculating propagators. Finite volume effects at the lowest quark mass are examined by using two different lattice volumes. Our results show that we achieve statistical errors of only a few percent. We plan to compute renormalization constants non-perturbatively and extend the calculation to two more lattice spacings and to the nucleons.
hep-latPoS(2007)·16 citations
16*
Results from overlap valence quarks on a twisted mass sea
Nicolas Garron🇩🇪 · Luigi Scorzato🇮🇹
We present results of lattice computations using overlap fermions on a twisted mass background. $N_{f} = 2$ full QCD gauge configurations have been produced by the ETM Collaboration with very light pions (down to less than 300 MeV), with small lattice spacing ( $a \approx 0.09$ fm) and large volumes ( $V / a^{4} = 2 4^{3} \times 48$ ). By profiting of the good chiral properties of the overlap operator for the valence quarks, it is also possible to have a precise (and unquenched) determination of those physical quantities where the chiral properties are crucial. In order to have unquenched results, we match the valence quark mass with the sea quark mass. We also perform computations with different quark masses in order to simulate (partially quenched) Strange and Charm quarks. A typical application is the computation of $B_{K}$ , for which we present first results.
hep-latPoS(2007)·9 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.