Disconnected contributions to hadronic structure: a new method for stochastic noise reduction

Collins, Sara

doi:10.22323/1.042.0141

Cited by 13 publications

(17 citation statements)

References 7 publications

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“…[24]. Valence quark masses are taken as fractional ratios of the tuned strange quark masses given in Table V [58] in an AMA setup [59] with 20 configurations solved with full precision and 1540 configurations solved with a residual of 10 −4 . The 20 full-precision solves are used to correct the bias introduced by this procedure, which was tuned to have negligible impact on the results.…”

Section: Numerical Setupmentioning

confidence: 99%

Consistency of hadronic vacuum polarization between lattice QCD and the R ratio

2020

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There are emerging tensions for theory results of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment both within recent lattice QCD calculations and between some lattice QCD calculations and R-ratio results. In this paper we work towards scrutinizing critical aspects of these calculations. We focus in particular on a precise calculation of Euclidean position-space windows defined by RBC/UKQCD that are ideal quantities for cross-checks within the lattice community and with R-ratio results. We perform a lattice QCD calculation using physical up, down, strange, and charm sea quark gauge ensembles generated in the staggered formalism by the MILC collaboration. We study the continuum limit using inverse lattice spacings from a −1 ≈ 1.6 GeV to 3.5 GeV, identical to recent studies by FNAL/HPQCD/MILC and Aubin et al. and similar to the recent study of BMW. Our calculation exhibits a tension for the particularly interesting window result of a ud,conn.,isospin,W µ from 0.4 fm to 1.0 fm with previous results obtained with a different discretization of the vector current on the same gauge configurations. Our results may indicate a difficulty related to estimating uncertainties of the continuum extrapolation that deserves further attention. In this work we also provide results for a ud,conn.,isospin µ , a s,conn.,isospin µ , a SIB,conn. µ for the total contribution and a large set of windows. For the total contribution, we find a HVP LO µ = 714(27)(13)10 −10 , a ud,conn.,isospin µ = 657(26)(12)10 −10 , a s,conn.,isospin µ = 52.83(22)(65)10 −10 , and a SIB,conn. µ = 9.0(0.8)(1.2)10 −10 , where the first uncertainty is statistical and the second systematic. We also comment on finite-volume corrections for the strong-isospin-breaking corrections.

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Section: Numerical Setupmentioning

confidence: 99%

Consistency of hadronic vacuum polarization between lattice QCD and the R ratio

2020

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“…Obviously, it is favorable in terms of the total computer time spent to increase the number of configurations instead of the number of inversions per configuration. We remark that the total number of exact inversions necessary to achieve a given error can be considerably reduced by methods like the hopping parameter expansion [60,61], truncated eigenmode substitution [62][63][64], the truncated solver method [65][66][67] and, in the case of Wilson-like fermions, employing spin-explicit stochastic sources [68][69][70].…”

Section: Statistical Accuracy and Disconnected Contributionsmentioning

confidence: 99%

Hadronic vacuum polarization and muong−2from magnetic susceptibilities on the lattice

Bali

Endrődi

2015

Phys. Rev. D

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We present and test a new method to compute the hadronic vacuum polarization function in lattice simulations. This can then be used, e.g., to determine the leading hadronic contribution to the anomalous magnetic moment of the muon. The method is based on computing susceptibilities with respect to external electromagnetic plane wave fields and allows for a precision determination of both the connected and the disconnected contributions to the vacuum polarization. We demonstrate that the statistical errors obtained with our method are much smaller than those quoted in previous lattice studies, primarily due to a very effective suppression of the errors of the disconnected terms. These turn out to vanish within small errors, enabling us to quote an upper limit. We also comment on the accuracy of the vacuum polarization function determined from present experimental -ratio data.

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“…Finally, a new method called the truncated solver method (TSM) introduced in [CBS07], was used to improve the computation of the stochastic estimates. In its basic form, it is based on two independent sets (set 1 and set 2) of noise sources with numbers of sources equal to N η,1 and N η,2 .…”

Section: Disconnected Contributionsmentioning

confidence: 99%

“…The numerical studies in [CBS07] were based on a mixed action approach using the Wilson action for the valence fermions together with gauge configurations for n f = 2 + 1 stout-link improved (rooted) staggered sea quarks and a Symanzik improved gauge action, for a lattice spacing of a ≈ 0.127 fm, and a physical volume of V ≈ (2.0 fm) 3 . Using a standard ratio of the disconnected parts of the three-point to the two-point function, the disconnected contribution to the nucleon spin, ∆q disc , was estimated for three different quark masses in the quark loop and 2 different quark masses in the nucleon 2-point correlators, corresponding to pion masses in the range of ≈ 300 MeV to ≈ 600 MeV.…”

Section: Disconnected Contributionsmentioning

confidence: 99%

Hadron structure from lattice quantum chromodynamics

2010

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This is a review of hadron structure physics from lattice QCD. Throughout this report, we place emphasis on the contribution of lattice results to our understanding of a number of fundamental physics questions related to, e.g., the origin and distribution of the charge, magnetization, momentum and spin of hadrons. Following an introduction to some of the most important hadron structure observables, we summarize the methods and techniques employed for their calculation in lattice QCD. We briefly discuss the status of relevant chiral perturbation theory calculations needed for controlled extrapolations of the lattice results to the physical point. In the main part of this report, we give an overview of lattice calculations on hadron form factors, moments of (generalized) parton distributions, moments of hadron distribution amplitudes, and other important hadron structure observables. Whenever applicable, we compare with results from experiment and phenomenology, taking into account systematic uncertainties in the lattice computations. Finally, we discuss promising results based on new approaches, ideas and techniques, and close with remarks on future perspectives of the field.

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Disconnected contributions to hadronic structure: a new method for stochastic noise reduction

Cited by 13 publications

References 7 publications

Consistency of hadronic vacuum polarization between lattice QCD and the R ratio

Consistency of hadronic vacuum polarization between lattice QCD and the R ratio

Hadronic vacuum polarization and muong−2from magnetic susceptibilities on the lattice

Hadron structure from lattice quantum chromodynamics

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