Gravitational form factors and angular momentum densities in light-front quark-diquark model

Kumar, Narinder; Mondal, Chandan; Sharma, Neetika

doi:10.1140/epja/i2017-12433-0

“…It is well known that both a scalar diquark and an axialvector diquark are needed to describe the phenomenology of up quarks and down quarks in the nucleon-see, for instance, Refs. [116][117][118]. In this section, we therefore explore contributions from the axial-vector diquark.…”

Section: Axial-vector Diquark Resultsmentioning

confidence: 99%

Exploring twist-2 GPDs through quasidistributions in a diquark spectator model

Bhattacharya

¹

,

Cocuzza

²

,

Metz

³

2020

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Quasi parton distributions (quasi-PDFs) are currently under intense investigation. Quasi-PDFs are defined through spatial correlation functions and are thus accessible in lattice QCD. They gradually approach their corresponding standard (light-cone) PDFs as the hadron momentum increases. Recently, we investigated the concept of quasi-distributions in the case of generalized parton distributions (GPDs) by calculating the twist-2 vector GPDs in the scalar diquark spectator model. In the present work, we extend this study to the remaining six leading-twist GPDs. For large hadron momenta, all quasi-GPDs analytically reduce to the corresponding standard GPDs. We also study the numerical mismatch between quasi-GPDs and standard GPDs for finite hadron momenta. Furthermore, we present results for quasi-PDFs, and explore higher-twist effects associated with the parton momentum and the longitudinal momentum transfer to the target. We study the dependence of our results on the model parameters as well as the type of diquark. Finally, we discuss the lowest moments of quasidistributions, and elaborate on the relation between quasi-GPDs and the total angular momentum of quarks. The moment analysis suggests a preferred definition of several quasidistributions.

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“…Here we can proceed "backwards" and integrate Eqs. (45), (46) to obtainDðrÞ. This is most conveniently done by integrating the expressions (45), (46) twice over the radial distances from r to infinity, where all densities vanish.…”

Section: B the D-term Form Factormentioning

confidence: 99%

Effects of long-range forces on the D -term and the energy-momentum structure

Varma

¹

,

Schweitzer

²

2020

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The hadronic form factors of the energy-momentum tensor (EMT) have attracted considerable interest in recent literature. This concerns especially the D-term form factor DðtÞ with its appealing interpretation in terms of internal forces. With their focus on hadron structure, theoretical studies so far have concentrated mainly on strongly interacting systems with short-range forces. Effects on the EMT due to long-range forces like the electromagnetic interaction have not yet been studied. Electromagnetic forces play a small role in the balance of forces inside the proton, but their long-range nature introduces new features which are not present in systems with short-range forces. We use a simple but consistent classical field theoretical model of the proton to show how the presence of long-range forces alters some notions taken for granted in short-range systems. Our results imply that a more careful definition of the D-term is required when longrange forces are present.

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“…Thus, several modeling frameworks have been used in the last few decades, each one having its advantages. For instance, we have the Nambu-Jona-Lasinio (NJL) model [63][64][65][66][67][68], the constituent quark model [69][70][71], the light-front holographic model [72][73][74], the light-front quark-diquark model [75][76][77], the AdS/QCD model [78][79][80], the chiral quark model [81,82] and the Dyson-Schwinger equations (DSEs) [7,8,83]. The NJL model has an effective Lagrangian of relativistic fermions interacting through local fermion-fermion couplings, and especially, it preserves one of the most important fundamental symmetries of QCD, namely, chiral symmetry.…”

Section: (): V-volmentioning

confidence: 99%

Kaon generalized parton distributions and light-front wave functions in the Nambu–Jona-Lasinio model

Zhang

¹

,

Ping

²

2021

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Kaon generalized parton distributions (GPDs) and the leading Fock state light-front wave functions are investigated in the framework of Nambu–Jona-Lasinio model with proper time regularization. In addition, we compared the form factors, parton distribution functions, and generalized form factors obtained from them, respectively. The first Mellin moments of GPDs result in the form factors of local currents. The second Mellin moments of vector GPDs are related to gravitational form factors, the quark mass distribution $$\theta _2$$ θ 2 and the quark pressure distribution $$\theta _1$$ θ 1 . When taking a Fourier transform of GPDs in impact parameter space, we can get the mean-squared impact parameter for the quarks of the kaon: $$\langle {\varvec{b}}_{\bot }^2\rangle _K^u=0.149$$ ⟨ b ⊥ 2 ⟩ K u = 0.149 fm$$^2$$ 2 , $$\langle {\varvec{b}}_{\bot }^2\rangle _K^s=0.088$$ ⟨ b ⊥ 2 ⟩ K s = 0.088 fm$$^2$$ 2 . This means that the kaon s quark is nearer to the center of transverse momentum than the u quark. We also give the light-cone energy radius for the quarks of the kaon from the mass distribution $$\theta _2$$ θ 2 : $$r_{E,LC}^{u,K}=0.187 $$ r E , L C u , K = 0.187 fm, $$ r_{E,LC}^{s,K}=0.167$$ r E , L C s , K = 0.167 fm, and the light-cone charge radius from quark form factors of the kaon: $$r_{c,LC}^{u,K}=0.390 $$ r c , L C u , K = 0.390 fm, $$r_{c,LC}^{s,K}=0.296 $$ r c , L C s , K = 0.296 fm, which means that the s quark has a smaller extent than the u quark. The light-front transverse-spin distributions $$\rho _u^1\left( {\varvec{b}}_{\bot },{\varvec{s}}_{\perp }\right) $$ ρ u 1 b ⊥ , s ⊥ and $$\rho _u^2\left( {\varvec{b}}_{\bot },{\varvec{s}}_{\perp }\right) $$ ρ u 2 b ⊥ , s ⊥ show distortions, the average shift are $$\langle b_{\bot }^y\rangle _1^u=0.116$$ ⟨ b ⊥ y ⟩ 1 u = 0.116 fm and $$\langle b_{\bot }^y\rangle _2^u=0.083$$ ⟨ b ⊥ y ⟩ 2 u = 0.083 fm. On the kinematic domain associated with the valence-quark dominance, the unpolarized Wigner distribution from light-front wave functions is sharply peaked. It extends as the transverse position variable increases in magnitude and has a domain of negative support. Through the comparison of distributions from the two methods, we find that they give the same multi-dimensional mapping of the kaon in the Nambu–Jona-Lasinio model.

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Gravitational form factors and angular momentum densities in light-front quark-diquark model

Cited by 23 publications

References 89 publications

Exploring twist-2 GPDs through quasidistributions in a diquark spectator model

Exploring twist-2 GPDs through quasidistributions in a diquark spectator model

Effects of long-range forces on the D -term and the energy-momentum structure

Kaon generalized parton distributions and light-front wave functions in the Nambu–Jona-Lasinio model

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