Nucleon structure from Lattice QCD using a nearly physical pion mass

Green, Jeremy R.; Engelhardt, Michael; Krieg, Stefan; Negele, John W.; Pochinsky, Andrew; Syritsyn, Sergey

doi:10.1016/j.physletb.2014.05.075

Cited by 81 publications

(140 citation statements)

References 44 publications

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“…However, they are so far restricted to moderately low Q 2 and still carry sizeable statistical errors; for example, the necessary precision for an unambiguous determination of the proton's charge radius is not yet within reach. Among other nucleon properties of interest are the axial coupling constant g A , which has been traditionally hard to reproduce on the lattice, as well as moments of structure functions and generalized parton distributions [257,397,465,466]. Concerning form factors, most efforts up to now have concentrated on the ground state octet baryons in the positive parity sector.…”

Section: Methodological Overviewmentioning

confidence: 99%

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Baryons as relativistic three-quark bound states

Eichmann

Sanchis-Alepuz

Williams

et al. 2016

Progress in Particle and Nuclear Physics

436

530

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We review the spectrum and electromagnetic properties of baryons described as relativistic three-quark bound states within QCD. The composite nature of baryons results in a rich excitation spectrum, whilst leading to highly non-trivial structural properties explored by the coupling to external (electromagnetic and other) currents. Both present many unsolved problems despite decades of experimental and theoretical research. We discuss the progress in these fields from a theoretical perspective, focusing on nonperturbative QCD as encoded in the functional approach via Dyson-Schwinger and Bethe-Salpeter equations. We give a systematic overview as to how results are obtained in this framework and explain technical connections to lattice QCD. We also discuss the mutual relations to the quark model, which still serves as a reference to distinguish 'expected' from 'unexpected' physics. We confront recent results on the spectrum of non-strange and strange baryons, their form factors and the issues of two-photon processes and Compton scattering determined in the DysonSchwinger framework with those of lattice QCD and the available experimental data. The general aim is to identify the underlying physical mechanisms behind the plethora of observable phenomena in terms of the underlying quark and gluon degrees of freedom.

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Section: Methodological Overviewmentioning

confidence: 99%

“…with m π = 138 MeV, have been performed in the past years for some selected observables, see e.g. [157][158][159]257] for reviews and results. Many other quantities, however, are just too cost-intensive and will be discussed later also for a range of heavier pion masses, some even as large as m π = 600 MeV.…”

Section: Extracting the Hadron Spectrum From Qcdmentioning

confidence: 99%

Baryons as relativistic three-quark bound states

Eichmann

Sanchis-Alepuz

Williams

et al. 2016

Progress in Particle and Nuclear Physics

436

530

View full text Add to dashboard Cite

show abstract

“…Recently, lattice QCD simulations for the nucleon became available for Q 2 = 0 [69][70][71][72][73][74][75][76], for finite Q 2 [77][78][79][80][81][82][83], and also for the octet baryons [84][85][86][87]. These studies are very important to understand the role of the valence quarks and of the meson cloud dressing.…”

Section: Introductionmentioning

confidence: 99%

Axial form factors of the octet baryons in a covariant quark model

Ramalho

Tsushima

2016

Phys. Rev. D

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We study the weak interaction axial form factors of the octet baryons, within the covariant spectator quark model, focusing on the dependence of four-momentum transfer squared, Q 2 . In our model the axial form factors GA(Q 2 ) (axial-vector form factor) and GP (Q 2 ) (induced pseudoscalar form factor), are calculated based on the constituent quark axial form factors and the octet baryon wave functions. The quark axial current is parametrized by the two constituent quark form factors, the axial-vector form factor g q A (Q 2 ), and the induced pseudoscalar form factor g q P (Q 2 ). The baryon wave functions are composed of a dominant S-state and a P -state mixture for the relative angular momentum of the quarks. First, we study in detail the nucleon case. We assume that the quark axial-vector form factor g q A (Q 2 ) has the same function form as that of the quark electromagnetic isovector form factor. The remaining parameters of the model, the P -state mixture and the Q 2 -dependence of g q P (Q 2 ), are determined by a fit to the nucleon axial form factor data obtained by lattice QCD simulations with large pion masses. In this lattice QCD regime the meson cloud effects are small, and the physics associated with the valence quarks can be better calibrated. Once the valence quark model is calibrated, we extend the model to the physical regime, and use the low Q 2 experimental data to estimate the meson cloud contributions for GA(Q 2 ) and GP (Q 2 ). Using the calibrated quark axial form factors, and the generalization of the nucleon wave function for the other octet baryon members, we make predictions for all the possible weak interaction axial form factors GA(Q 2 ) and GP (Q 2 ) of the octet baryons. The results are compared with the corresponding experimental data for GA(0), and with the estimates of baryon-meson models based on SU (6) symmetry.

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“…Most attempts have resulted in values ∼10% below the experimental number for the axial-vector coupling [1][2][3][4][5][6][7][8], while a few claim that their results could be consistent with experiment [9][10][11][12]. For the quark momentum fraction x u−d , overestimation by ∼20 -30% is common in most of the calculations [3,7,[13][14][15] except [8].…”

Section: Introductionmentioning

confidence: 99%

“…For the quark momentum fraction x u−d , overestimation by ∼20 -30% is common in most of the calculations [3,7,[13][14][15] except [8].…”

Section: Introductionmentioning

confidence: 99%

Stochastic method with low mode substitution for nucleon isovector matrix elements

et al. 2016

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We introduce a stochastic method with low-mode substitution to evaluate the connected threepoint functions. The isovector matrix elements of the nucleon for the axial-vector coupling g 3 A , scalar couplings g 3 S and the quark momentum fraction x u−d are calculated with overlap fermion on 2+1 flavor domain-wall configurations on a 24 3 ×64 lattice at mπ = 330 MeV with lattice spacing a = 0.114 fm.

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Nucleon structure from Lattice QCD using a nearly physical pion mass

Cited by 81 publications

References 44 publications

Baryons as relativistic three-quark bound states

Baryons as relativistic three-quark bound states

Axial form factors of the octet baryons in a covariant quark model

Stochastic method with low mode substitution for nucleon isovector matrix elements

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