Nucleon form factors and root-mean-square radii on a 
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 lattice at the physical point

Shintani, Eigo; Ishikawa, Ken-ichi; Kuramashi, Y.; Sasaki, Shoichi; Yamazaki, Takeshi

doi:10.1103/physrevd.99.014510

Cited by 90 publications

(69 citation statements)

References 57 publications

(170 reference statements)

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“…Given our demonstration in Sec. VII that a large part of the difference between data obtained by various collaborations is an artifact of scale setting, the major advantage of the PACS'18A [56] calculation is that the large volume provides data at Q 2 < 0.1 GeV 2 ; the agreement between data from different collaborations presented in Sec. VII indicates that finite volume corrections are already small for M π L ≈ 4.…”

Section: Discussionmentioning

confidence: 99%

Nucleon electromagnetic form factors in the continuum limit from ( 2+1+1 )-flavor lattice QCD

et al. 2020

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We present results for the isovector (p−n) electromagnetic form factors of the nucleon using eleven ensembles of gauge configurations generated by the MILC collaboration using the highly improved staggered quark (HISQ) action with 2+1+1 dynamical flavors. These ensembles span four lattice spacings a ≈ 0.06, 0.09, 0.12 and 0.15 fm and three values of the light-quark masses corresponding to the pion masses Mπ ≈ 135, 225 and 315 MeV. High-statistics estimates using the truncated solver method method allow us to quantify various systematic uncertainties and perform a simultaneous extrapolation in the lattice spacing, lattice volume and light-quark masses. We analyze the Q 2 dependence of the form factors calculated over the range 0.05 Q 2 ∼ 1.4 GeV 2 using both the model independent z-expansion and the dipole ansatz. Our final estimates, using the z-expansion fit, for the isovector root-mean-square radius of nucleon are rE = 0.769 (27)(30) fm, rM = 0.671(48)(76) fm and µ p−n = 3.939(86)(138) Bohr magneton. The first error is the combined uncertainty from the leading-order analysis, and the second is an estimate of the additional uncertainty due to using the leading order chiral-continuum-finite-volume fits. The estimates from the dipole ansatz, rE = 0.765(11)(8) fm, rM = 0.704(21)(29) fm and µ p−n = 3.975(84)(125) Bohr magneton, are consistent with those from the z-expansion but with smaller errors. Our analysis highlights three points. First, all our data for form factors from the eleven ensembles and existing lattice data on, or close to, physical mass ensembles from other collaborations collapses more clearly onto a single curve when plotted versus Q 2 /M 2 N as compared to Q 2 with the scale set by quantities other than MN . The difference between these two ways of analyzing the data is indicative of discretization errors, some of which presumably cancel when the data are plotted versus Q 2 /M 2 N . Second, the size of the remaining deviation of this common curve from the Kelly curve is small and can be accounted for by statistical and possible systematic uncertainties. Third, to improve lattice estimates for r 2 E , r 2 M and µ, high statistics data for Q 2 < 0.1 GeV 2 are needed.

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Section: Discussionmentioning

confidence: 99%

Nucleon electromagnetic form factors in the continuum limit from ( 2+1+1 )-flavor lattice QCD

et al. 2020

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“…Conclusions.-All previous lattice calculations of the three form factors G A ,G P , and G P showed significant violations of the PCAC relation, Eq. (3) [6][7][8][9][10][11][12]. This failure had cast doubts on the lattice methodology for extracting nucleon form factors.…”

Section: -4mentioning

confidence: 99%

“…(9). The A 4 correlators have traditionally [6][7][8][9][10][11][12] been neglected because fits with E i and M i obtained from C 2pt are poor, as shown in Fig. 2 (top left panel).…”

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confidence: 99%

Axial Vector Form Factors from Lattice QCD that Satisfy the PCAC Relation

et al. 2020

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Previous lattice QCD calculations of axial vector and pseudoscalar form factors show significant deviation from the partially conserved axial current (PCAC) relation between them. Since the original correlation functions satisfy PCAC, the observed deviations from the operator identity cast doubt on whether all of the systematics in the extraction of form factors from the correlation functions are under control. We identify the problematic systematic as a missed excited state, whose energy as a function of the momentum transfer squared Q 2 is determined from the analysis of the three-point functions themselves. Its energy is much smaller than those of the excited states previously considered, and including it impacts the extraction of all of the ground state matrix elements. The form factors extracted using these mass and energy gaps satisfy PCAC and another consistency condition, and they validate the pion-pole dominance hypothesis. We also show that the extraction of the axial charge g A is very sensitive to the value of the mass gaps of the excited states used, and current lattice data do not provide an unambiguous determination of these, unlike the Q 2 ≠ 0 case. To highlight the differences and improvement between the conventional vs the new analysis strategy, we present a comparison of results obtained on a physical pion mass ensemble at a ≈ 0.0871 fm. With the new strategy, we find g A ¼ 1.30ð6Þ and axial charge radius r A ¼ 0.74ð6Þ fm, both extracted using the z expansion to parametrize the Q 2 behavior of G A ðQ 2 Þ, and g Ã P ¼ 8.06ð44Þ, obtained using the pion-pole dominance ansatz to fit the Q 2 behavior of the induced pseudoscalar form factor G P ðQ 2 Þ. These results are consistent with current phenomenological values.

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“…A representative set of recent work can be found in Refs. [60][61][62][63][64][65][66][67][68][69][70][71][72][73][74] Significant improvements have been made to investigate the quark-mass, finite-volume, and finite-lattice-spacing dependence, and the effects of excited-state contamination in the correlation functions. With these technical and algorithmic advances, lattice QCD can calculate not only the isovector contribution but also the computationally more demanding isoscalar and strange-quark contributions, which are needed for neutral-current processes, discussed below.…”

Section: A Nucleon Form Factorsmentioning

confidence: 99%

Lattice QCD and neutrino-nucleus scattering

et al. 2019

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This document is one of a series of whitepapers from the USQCD collaboration. Here, we discuss opportunities for lattice QCD in neutrino-oscillation physics, which inevitably entails nucleon and nuclear structure. In addition to discussing pertinent lattice-QCD calculations of nucleon and nuclear matrix elements, the interplay with models of nuclei is discussed. This program of lattice-QCD calculations is relevant to current and upcoming neutrino experiments, becoming increasingly important on the timescale of LBNF/DUNE and HyperK. * Editor, ask@fnal.gov † Editor, dgr@jlab.org arXiv:1904.09931v1 [hep-lat]

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Nucleon form factors and root-mean-square radii on a (10.8 fm)4 lattice at the physical point

Cited by 90 publications

References 57 publications

Nucleon electromagnetic form factors in the continuum limit from ( 2+1+1 )-flavor lattice QCD

Nucleon electromagnetic form factors in the continuum limit from ( 2+1+1 )-flavor lattice QCD

Axial Vector Form Factors from Lattice QCD that Satisfy the PCAC Relation

Lattice QCD and neutrino-nucleus scattering

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