Lattice Calculations of Nucleon Form Factors

Syritsyn, Sergey; Armstrong, David; Burkert, Volker; Chen, Jianping; Detmold, Will; Dudek, Jo; Melnitchouk, Wally; Richards, David

doi:10.1063/1.3647148

Cited by 6 publications

(20 citation statements)

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“…C depend on a particular γ 5 definition in terms of γ µ , but the numerical lattice results are invariant as long as the same [γ 5 ] Euc is used in both Eqs. (54) and (30).…”

Section: Appendix A: Conventionsmentioning

confidence: 99%

“…We compute nucleon-current three-and four-point correlators with two source-sink separation values t sep = {8, 10}a = {0.91, 1.15} fm for the 16 3 × 32 ensemble, and three t sep = {8, 10, 12}a = {0.88, 1.11, 1.33} fm for the 24 3 × 64 ensemble. For the 24 3 × 64 lattice, we use the Gaussian-smeared sources with APE-smeared gauge links using parameters optimized for overlap with the ground state [30], while for the 16 3 × 32 ensemble we used the smearing parameters from Ref. [11].…”

Section: A Parity-even and -Odd Nucleon Correlatorsmentioning

confidence: 99%

“…The system of equations for form factors is reduced by combining equivalent equations to reduce the system dimension and make estimation of the covariance matrix more stable (see, e.g., Ref. [30] for details). The quark current operator is renormalized using renormalization constants Z V = 0.71408 for 24 3 ×64 [27] and the chiral-limit value Z V = Z A = 0.7162 for 16 3 × 32 [31] ensembles.…”

Section: B Nucleon Form Factorsmentioning

confidence: 99%

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Lattice calculation of electric dipole moments and form factors of the nucleon

et al. 2017

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We analyze commonly used expressions for computing the nucleon electric dipole form factors (EDFF) F3 and moments (EDM) on a lattice and find that they lead to spurious contributions from the Pauli form factor F2 due to inadequate definition of these form factors when parity mixing of lattice nucleon fields is involved. Using chirally symmetric domain wall fermions, we calculate the proton and the neutron EDFF induced by the CP-violating quark chromo-EDM interaction using the corrected expression. In addition, we calculate the electric dipole moment of the neutron using background electric field that respects time translation invariance and boundary conditions, and find that it decidedly agrees with the new formula but not the old formula for F3. Finally, we analyze some selected lattice results for the nucleon EDM and observe that after the correction is applied, they either agree with zero or are substantially reduced in magnitude, thus reconciling their difference from phenomenological estimates of the nucleon EDM.

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“…C depend on a particular γ 5 definition in terms of γ µ , but the numerical lattice results are invariant as long as the same [γ 5 ] Euc is used in both Eqs. (54) and (30).…”

Section: Appendix A: Conventionsmentioning

confidence: 99%

Section: A Parity-even and -Odd Nucleon Correlatorsmentioning

confidence: 99%

Section: B Nucleon Form Factorsmentioning

confidence: 99%

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Lattice calculation of electric dipole moments and form factors of the nucleon

et al. 2017

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“…Lattice QCD provides a systematically improvable technique to study nonperturbative features of QCD, and hence offers significant potential to give valuable insight into the spin decomposition of the nucleon. Recent results have been published in [6][7][8][9] -also see the lattice review [10]. Nevertheless, there are still challenges in the lattice formulation, particularly those associated with the simulation of so-called "disconnected" quantities.…”

mentioning

confidence: 99%

Feynman-Hellmann approach to the spin structure of hadrons

et al. 2014

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We perform a N f = 2 + 1 lattice QCD simulation to determine the quark spin fractions of hadrons using the Feynman-Hellmann theorem. By introducing an external spin operator to the fermion action, the matrix elements relevant for quark spin fractions are extracted from the linear response of the hadron energies. Simulations indicate that the Feynman-Hellmann method offers statistical precision that is comparable to the standard three-point function approach, with the added benefit that it is less susceptible to excited state contamination. This suggests that the Feynman-Hellmann technique offers a promising alternative for calculations of quark line disconnected contributions to hadronic matrix elements. At the SU(3)-flavour symmetry point, we find that the connected quark spin fractions are universally in the range 55-70% for vector mesons and octet and decuplet baryons. There is an indication that the amount of spin suppression is quite sensitive to the strength of SU (3) breaking.

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“…Although the availability of several longitudinal proton momenta in the gathered data set allowed for an ad hoc estimation of the large-ζ limit, calculations at larger proton momenta are clearly desirable. In this respect, the improved proton sources explored in [41,42] provide a perspective for generating data that permit a more quantitative treatment of the large-ζ limit.…”

Section: Discussionmentioning

confidence: 99%

Quark orbital dynamics in the proton from lattice QCD: From Ji to Jaffe-Manohar orbital angular momentum

Engelhardt

2017

Phys. Rev. D

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Given a Wigner distribution simultaneously characterizing quark transverse positions and momenta in a proton, one can directly evaluate their cross-product, i.e., quark orbital angular momentum. The aforementioned distribution can be obtained by generalizing the proton matrix elements of quark bilocal operators which define transverse momentum-dependent parton distributions (TMDs); the transverse momentum information is supplemented with transverse position information by introducing an additional nonzero momentum transfer. A gauge connection between the quarks must be specified in the quark bilocal operators; the staple-shaped gauge link path used in TMD calculations yields the Jaffe-Manohar definition of orbital angular momentum, whereas a straight path yields the Ji definition. An exploratory lattice calculation, performed at the pion mass mπ = 518 MeV, is presented which quasi-continuously interpolates between the two definitions and demonstrates that their difference can be clearly resolved. The resulting Ji orbital angular momentum is confronted with traditional evaluations based on Ji's sum rule. Jaffe-Manohar orbital angular momentum is enhanced in magnitude compared to its Ji counterpart.

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Lattice Calculations of Nucleon Form Factors

Cited by 6 publications

References 0 publications

Lattice calculation of electric dipole moments and form factors of the nucleon

Lattice calculation of electric dipole moments and form factors of the nucleon

Feynman-Hellmann approach to the spin structure of hadrons

Quark orbital dynamics in the proton from lattice QCD: From Ji to Jaffe-Manohar orbital angular momentum

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