Baryonic and mesonic 3-point functions with open spin indices

Bali, Gunnar S.; Collins, Sara; Gläßle, Benjamin; Heybrock, Simon; Korcyl, Piotr; Löffler, Marius; Rödl, Rudolf; Schäfer, Andreas

doi:10.1051/epjconf/201817506014

Cited by 11 publications

(12 citation statements)

References 9 publications

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“…Using the common sequential source method [92] the computational cost of evaluating three-point functions is high because a new inversion is necessary for each sink setup (timeslice, momentum and interpolating current). To reduce the computational cost and maximize synergies in calculating matrix elements we implemented a stochastic algorithm [93,94] which circumvents this limitations. The implementation we propose parallelizes the computations in such a way that those for multiple source positions and multiple insertion positions can be done simultaneously.…”

Section: Appendix B: Operators and Matrix Element Decompositionmentioning

confidence: 99%

Mellin moments of spin dependent and independent PDFs of the pion and rho meson

Löffler,

Wein,

Wurm

et al. 2021

Preprint

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We compute the second moments of pion and rho parton distribution functions (PDFs) in lattice QCD with N f = 2 + 1 flavors of improved Wilson fermions. We determine both singlet and nonsinglet flavor combinations and, for the first time, take disconnected contributions fully into account. In the case of the rho, we also calculate the additional contribution arising from the b1 structure function. The numerical analysis includes 26 ensembles, mainly generated by the CLS effort, with pion masses ranging from 420 MeV down to 214 MeV and with 5 different lattice spacings in the range of 0.1 fm to 0.05 fm. This enables us to take the continuum limit, as well as to resolve the quark mass dependencies reliably. Additionally we discuss the contaminations of rho correlation functions by two-pion states.

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Section: Appendix B: Operators and Matrix Element Decompositionmentioning

confidence: 99%

Mellin moments of spin dependent and independent PDFs of the pion and rho meson

Löffler,

Wein,

Wurm

et al. 2021

Preprint

Self Cite

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“…We used a modified version of the Chroma [160] software package along with the LibHadronAnalysis library [161] and improved inverters [88,[162][163][164]. The configurations were generated as part of the CLS effort [86,92] using openQCD (https://luscher.web.cern.ch/luscher/openQCD/) [88].…”

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confidence: 99%

Nucleon axial structure from lattice QCD

Bali

Barca

Collins

et al. 2020

J. High Energ. Phys.

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We present a new analysis method that allows one to understand and model excited state contributions in observables that are dominated by a pion pole. We apply this method to extract axial and (induced) pseudoscalar nucleon isovector form factors, which satisfy the constraints due to the partial conservation of the axial current up to expected discretization effects. Effective field theory predicts that the leading contribution to the (induced) pseudoscalar form factor originates from an exchange of a virtual pion, and thus exhibits pion pole dominance. Using our new method, we can recover this behavior directly from lattice data. The numerical analysis is based on a large set of ensembles generated by the CLS effort, including physical pion masses, large volumes (with up to 96 3 × 192 sites and Lm π = 6.4), and lattice spacings down to 0.039 fm, which allows us to take all the relevant limits. We find that some observables are much more sensitive to the choice of parametrization of the form factors than others. On the one hand, the z-expansion leads to significantly smaller values for the axial dipole mass than the dipole ansatz (M z-exp A = 1.02(10) GeV versus M dipole A = 1.31(8) GeV). On the other hand, we find that the result for the induced pseudoscalar coupling at the muon capture point is almost independent of the choice of parametrization (g z-exp P = 8.68(45) and g dipole P = 8.30(24)), and is in good agreement with both, chiral perturbation theory predictions and experimental measurement via ordinary muon capture. We also determine the axial coupling constant g A .

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“…where 3m = tr M. We non-perturbatively determine the renormalization with respect to the intermediate RI'-SMOM scheme and employ the improvement coefficients b J (g 2 ) of [11], where first estimates ofb J were found to be compatible with zero. With the exception of the m = m s ensembles the three-point correlation functions are computed using the stochastic method described in [12] (see also [13,14,15,16]), estimating a timeslice-to-all propagator (depicted as a wiggly line in figure 1). This allows us to factorize the three-point correlation function into two parts, the spectator part S and the insertion part I,…”

Section: Definitions Numerical Methods and The Fit Proceduresmentioning

confidence: 99%

Hyperon couplings from $N_f = 2 + 1$ lattice QCD

Simon¹,

Bali²,

Collins³

et al. 2019

Proceedings of 37th International Symposium on Lattice Field Theory — PoS(LATTICE2019)

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We compute various (generalized) isovector charges of the octet baryons. These include g A , g T and g S as well as the unpolarized, polarized and transversity parton distribution function (PDF) momentum fractions x u + −d + , x ∆u − −∆d − and x δ u + −δ d +. The simulations are carried out on a subset of the (isospin symmetric) N f = 2 + 1 flavour Coordinated Lattice Simulations (CLS) gauge ensembles with lattice spacings ranging from a ≈ 0.086 fm down to a ≈ 0.050 fm. First results on the breaking of flavour symmetry and the low energy constants F and D are presented. While SU(3) flavour symmetry violations are found to be sizeable for g A = 1 ∆u + −∆d + , these are quite small for g T = 1 δ u − −δ d − and x u + −d + .

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Baryonic and mesonic 3-point functions with open spin indices

Cited by 11 publications

References 9 publications

Mellin moments of spin dependent and independent PDFs of the pion and rho meson

Mellin moments of spin dependent and independent PDFs of the pion and rho meson

Nucleon axial structure from lattice QCD

Hyperon couplings from $N_f = 2 + 1$ lattice QCD

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