QCD with dynamical Wilson fermions. II

Gupta, Rajan; Baillie, C.F.; Brickner, Ralph G.; Kilcup, Gregory W.; Patel, Apoorva; Sharpe, Stephen R.

doi:10.1103/physrevd.44.3272

Cited by 62 publications

(84 citation statements)

References 24 publications

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“…5 represent data obtained in two-flavor full QCD using the nucleon mass derivative dm N /dm q [18], showing an agreement with quenched estimates (filled circles and diamonds) in the region of heavy quark with m π /m ρ > 0.7 − 0.8. We find these results to be quite encouraging.…”

Section: π-N σ Term -Recent Lattice Resultssupporting

confidence: 55%

“…[18]), which are a factor 2 − 3 smaller than in the quenched case. Since values of matrix elements are similar between the two cases, this means that the σ term is also small σ ≈ 20MeV in full QCD.…”

Section: π-N σ Term -Recent Lattice Resultsmentioning

confidence: 97%

“…It does not seem to arise from the effect of quenching since full QCD estimates plotted by upward triangles [18] do not deviate from quenched results. Effects of scaling violations also seem small since results from two values of β at 5.7 [13] and at 6.0 [18,30,31] are in agreement. One may suspect a possible ambiguity in the choice of the renormalization constant Z A , especially because the ratio F A /D A agrees with experiments.…”

Section: Isovector Axial Coupling G Amentioning

confidence: 93%

“…In particular the anomaly relation (5) fails in quenched QCD due to the double pole in the η ′ meson propagator connecting the disconnected quark loop and the nucleon [19]. For these reasons, only a few attempts have been made with these methods in the past [18,17].…”

Section: Other Methodsmentioning

confidence: 99%

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New developments in lattice QCD: Calculation of flavor singlet nucleon matrix elements and hadron scattering lengths

Okawa

1996

Nuclear Physics B - Proceedings Supplements

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Recent developments in lattice QCD calculation of flavor singlet nucleon matrix elements are reviewed. Substantial sea quark contributions are found in the π-N σ term and the quark spin content of the nucleon such that the total magnitude including valence contributions is in reasonable agreement with experiments. Some problems with flavor non-singlet nucleon matrix elements are pointed out. Recent work on lattice QCD calculation of hadron scattering length is also discussed.

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Section: π-N σ Term -Recent Lattice Resultssupporting

confidence: 55%

Section: π-N σ Term -Recent Lattice Resultsmentioning

confidence: 97%

Section: Isovector Axial Coupling G Amentioning

confidence: 93%

Section: Other Methodsmentioning

confidence: 99%

See 2 more Smart Citations

New developments in lattice QCD: Calculation of flavor singlet nucleon matrix elements and hadron scattering lengths

Okawa

1996

Nuclear Physics B - Proceedings Supplements

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“…Technically the fit formulae that we employ, eqs. (6,8) are true only for the complete correlation function. The best way to circumvent this problem and others is to make simulations at different strange quark masses; differentiation as in eq.…”

Section: Discussionmentioning

confidence: 99%

The πN sigma term — an evaluation using staggered fermions

Altmeyer

Göckeler

Horsley

et al. 1994

Nuclear Physics B - Proceedings Supplements

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A lattice calculation of the πN sigma term is described using dynamical staggered fermions. Preliminary results give a sea term comparable in magnitude to the valence term. Theoretical DiscussionPreprint HLRZ 93-70 November 1993 The πN sigma term, σ πN , is defined as that part of the mass of the nucleon coming from the expectation value of the up (u) and down (d) quark mass terms in the QCD Hamiltonian,where we have taken these quarks to have equal current mass (= m). Other contributions to the nucleon mass come from the chromo-electric and chromo-magnetic gluon pieces and the sea terms due to the s quarks. Experimentally this matrix element has been measured from low energy π-N scattering, [1]. A delicate extrapolation to the chiral limit [2] gives a result for the isospin even amplitude of Σ/f 2 π with Σ = σ πN , from which the πN sigma term may be found. The precise value obtained this way has been under discussion for many years. For orientation we shall just quote a range of results from later analyses of σ πN ≈ 56MeV, [3], down to 45MeV, [4].To estimate valence and sea contributions to σ πN , classical current algebra analyses assume octet dominance and make first order perturbation theory about the SU F (3) flavour symmetric Hamiltonian. This gives where we have first assumed that the nucleon wavefunction does not change much around the symmetric point. We then subtract and add a strange component. At the symmetric point the u and d quarks each have equal valence and sea part, while the s quark matrix element only has a sea component. Thus in the first term the sea contribution cancels, justifying the definitions given in eq. (2). Using first order perturbation theory for the baryon mass splittings σ val πN may be calculated to give σ val πN ≈ 25MeV and so σ sea πN ≈ 31 ∼ 20MeV. This in turn means that m s N |ss|N ≈ 400 ∼ 250MeV, which would indicate a sizeable portion of the nucleon mass (938MeV) comes from the strange quark contribution. Measuring σ πNWe now turn to our lattice calculation. We have generated configurations using dynamical staggered fermions on a 16 3 × 24 lattice at β = 5.35, m = 0.01 (plus some larger masses), [5]. Practically there are several possibilities open to us for the evaluation of the matrix element. The easiest is simply to differentiate the shift operator S 4 giving(the Feynman-Hellmann theorem). Thus we need to measure M N for different masses m and numerically estimate the gradient. This leads to σ πN ≈ 11.9(8)m| m=0.01 ≈ 0.12(1),

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Light hadron physics from the lattice

Negele

Chiral Dynamics: Theory and Experiment

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QCD with dynamical Wilson fermions. II

Cited by 62 publications

References 24 publications

New developments in lattice QCD: Calculation of flavor singlet nucleon matrix elements and hadron scattering lengths

New developments in lattice QCD: Calculation of flavor singlet nucleon matrix elements and hadron scattering lengths

The πN sigma term — an evaluation using staggered fermions

Light hadron physics from the lattice

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