Flavor singlet meson mass in the continuum limit in two-flavor lattice QCD

We suggest a new (dynamical) Abelian projection of the lattice QCD. It contains no gauge condition imposed on gauge fields so that Gribov copying is avoided. Configurations of gauge fields that turn into monopoles in the Abelian projection can be classified in a gauge-invariant way. In the continuum limit, the theory respects the Lorentz invariance. A similar dynamical reduction of the gauge symmetry is proposed for studies of gauge-variant correlators (like a gluon propagator) in the lattice QCD. Though the procedure is harder for numerical simulations, it is free of gauge-fixing artifacts, like the Gribov horizon and copies.

Download Full-text

Charm sea effects on charmonium decay constants and heavy meson masses

The European Physical Journal C ◽

10.1140/epjc/s10052-021-09520-y ◽

2021 ◽

Vol 81 (8) ◽

Author(s):

Salvatore Calì ◽

Kevin Eckert ◽

Jochen Heitger ◽

Francesco Knechtli ◽

Tomasz Korzec

Keyword(s):

Lattice Qcd ◽

Continuum Limit ◽

Charm Quark ◽

Heavy Meson ◽

Charm Quarks ◽

Decay Constants ◽

Derivatives Of ◽

Charm Mass ◽

The Continuum

AbstractWe estimate the effects on the decay constants of charmonium and on heavy meson masses due to the charm quark in the sea. Our goal is to understand whether for these quantities $${N_\mathrm{f}}=2+1$$ N f = 2 + 1 lattice QCD simulations provide results that can be compared with experiments or whether $${N_\mathrm{f}}=2+1+1$$ N f = 2 + 1 + 1 QCD including the charm quark in the sea needs to be simulated. We consider two theories, $${N_\mathrm{f}}=0$$ N f = 0 QCD and QCD with $${N_\mathrm{f}}=2$$ N f = 2 charm quarks in the sea. The charm sea effects (due to two charm quarks) are estimated comparing the results obtained in these two theories, after matching them and taking the continuum limit. The absence of light quarks allows us to simulate the $${N_\mathrm{f}}=2$$ N f = 2 theory at lattice spacings down to 0.023 fm that are crucial for reliable continuum extrapolations. We find that sea charm quark effects are below 1% for the decay constants of charmonium. Our results show that decoupling of charm works well up to energies of about 500 MeV. We also compute the derivatives of the decay constants and meson masses with respect to the charm mass. For these quantities we again do not see a significant dynamical charm quark effect, albeit with a lower precision. For mesons made of a charm quark and a heavy antiquark, whose mass is twice that of the charm quark, sea effects are only about 1‰ in the ratio of vector to pseudoscalar masses.

Download Full-text

THE CHIRAL U(1) SYMMETRY IN LATTICE QCD WITH WILSON FERMIONS

International Journal of Modern Physics A ◽

10.1142/s0217751x95001108 ◽

1995 ◽

Vol 10 (15) ◽

pp. 2269-2290 ◽

Cited By ~ 3

Author(s):

CARLO UNGARELLI

Keyword(s):

Lattice Qcd ◽

Chiral Symmetry ◽

Continuum Limit ◽

Axial Current ◽

Numerical Results ◽

Ward Identities ◽

Definition Of ◽

The Continuum ◽

Wilson Fermions

The properties of singlet flavor chiral symmetry of lattice QCD with Wilson fermions are analyzed. We show that a suitable U(1) axial current can be defined, satisfying, in the continuum limit, the Adler-Bell-Jackiw anomaly. Moreover, the renormalization properties of composite operators which appear in U(1) chiral Ward identities are discussed. Finally, starting from the renormalized Ward identities for the axial U(1) current, we analyze a definition of topological susceptibility suitable for nonperturbative studies and discuss preliminary numerical results.

Download Full-text

A STUDY OF GLUON PROPAGATOR ON COARSE LATTICE

Modern Physics Letters A ◽

10.1142/s0217732300000220 ◽

2000 ◽

Vol 15 (04) ◽

pp. 229-244 ◽

Cited By ~ 11

Author(s):

J. P. MA

Keyword(s):

Lattice Qcd ◽

Smooth Function ◽

Qualitative Agreement ◽

Lattice Spacing ◽

Continuum Limit ◽

Gluon Propagator ◽

Landau Gauge ◽

Lattice Action ◽

Lattice Volume ◽

The Continuum

We study gluon propagator in Landau gauge with lattice QCD, where we use an improved lattice action. The calculation of gluon propagator is performed on lattices with the lattice spacing from 0.40 fm to 0.24 fm and with the lattice volume from (2.40 fm )4 to (4.0 fm )4. We find that the rotation invariance is approximately restored in the q2-range, indicated by the fact that the propagator is a smooth function of the continuum momentum q2. We try to fit our results by two different ways, in the first one we interpret the calculated gluon propagators as a function of the continuum momentum, while in the second we interpret the propagators as a function of the lattice momentum. In both cases we use models which are the same in continuum limit. A qualitative agreement between two fittings is found.

Download Full-text