Non-perturbative tests of continuum HQET through small-volume two-flavour QCD

Fritzsch, Patrick; Garrón, Nicolas; Heitger, Jochen

doi:10.1007/jhep01(2016)093

Cited by 6 publications

(7 citation statements)

References 75 publications

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“…Although not necessary for O(a) improvement of physical quantities [23] (at maximal twist), it has been shown to reduce O(a 2 ) artifacts in some cases [25], and more importantly gives us access to the wide range of renormalization factors that have been determined non-perturbatively in the past. In particular we benefit from the knowledge of the critical mass m cr [26,27] and the axial current and pseudoscalar density renormalization factors Z A [28][29][30] and Z P [26,31]. Since one of our goals is a detailed understanding of charm related lattice artifacts, we simulate also at very fine lattice spacings, much finer than what is currently feasible in simulations that include light quarks.…”

Section: Actions and Algorithmsmentioning

confidence: 99%

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How much do charm sea quarks affect the charmonium spectrum?

2019

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The properties of charmonium states are or will be intensively studied by the B-factories Belle II and BESIII, the LHCb and PANDA experiments and at a future Super-c-τ Factory. Precise lattice calculations provide valuable input and several results have been obtained by simulating up, down and strange quarks in the sea. We investigate the impact of a charm quark in the sea on the charmonium spectrum, the renormalization group invariant charm-quark mass M c and the scalar charm-quark content of charmonium. The latter is obtained by the direct computation of the mass-derivatives of the charmonium masses. We do this investigation in a model, QCD with two degenerate charm quarks. The absence of light quarks allows us to reach very small lattice spacings down to 0.023 fm. By comparing to pure gauge theory we find that charm quarks in the sea affect the hyperfine splitting at a level below 2%. The most significant effects are 5% in M c and 3% in the value of the charm quark content of the η c meson. Given that we simulate two charm quarks these estimates are upper bounds for the contribution of a single charm quark. We show that lattice spacings < 0.06 fm are needed for safe continuum extrapolations of the charmonium spectrum with O(a) improved Wilson quarks. A useful relation for the projection to the desired parity of operators in two-point functions computed with twisted mass fermions is proven.

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Section: Actions and Algorithmsmentioning

confidence: 99%

“…It is given by the value at which m PCAC = 0. Instead of determining it ourselves, we use very precise critical masses obtained in [26,27]. These were computed from slightly different correlation functions in a finite volume, and differ from ours by an O(a) lattice artifact.…”

Section: Pcac Massmentioning

confidence: 99%

How much do charm sea quarks affect the charmonium spectrum?

2019

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“…The spatial dimensions are kept periodic. Moreover, for the production of our ensembles we benefit from the knowledge of the critical mass m cr [30,31] and the axial current and pseudoscalar density renormalization factors Z A [32][33][34] and Z P [30,35]. For further details about the simulations we refer to our previous works [12,22] and references therein.…”

Section: Numerical Setupmentioning

confidence: 99%

Charm sea effects on charmonium decay constants and heavy meson masses

et al. 2021

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We 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.

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“…To achieve maximal twist, the hopping parameter κ has been set to its critical value by interpolating the data published in Refs. [6,7]. Open boundary conditions in the temporal direction are imposed to keep auto-correlation times associated with the topological charge manageable [8].…”

Section: Numerical Setupmentioning

confidence: 99%

Comparison between models of QCD with and without dynamical charm quarks

Calì¹,

Knechtli²,

Korzec³

2019

Proceedings of the 36th Annual International Symposium on Lattice Field Theory — PoS(LATTICE2018)

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We investigate the influence of dynamical charm quarks on observables that depend explicitly on the charm quark fields, like the pseudo-scalar and vector masses m η c and m J/ψ , the hyperfine splitting (m J/ψ − m η c)/m η c , the charm quark mass and the meson decay constants. For this purpose, instead of working in full QCD we study a simplified setup. We simulate two theories: N f = 0 QCD and QCD with N f = 2 dynamical quarks at the charm mass. The absence of light quarks allows us to reach extremely fine lattice spacings (0.02 fm < a < 0.05 fm) which are crucial for reliable continuum extrapolations. Our main result is a comparison of various quantities in the continuum limit. For the hyperfine splitting we find that the effects of a dynamical charm quark are below our statistical precision of 2%.

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Non-perturbative tests of continuum HQET through small-volume two-flavour QCD

Cited by 6 publications

References 75 publications

How much do charm sea quarks affect the charmonium spectrum?

How much do charm sea quarks affect the charmonium spectrum?

Charm sea effects on charmonium decay constants and heavy meson masses

Comparison between models of QCD with and without dynamical charm quarks

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