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The gluon mass generation mechanism： A concise primer

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Frontiers of physics 2016年第2期11卷 131-148页

作者： A. C. Aguilar D. binosi J. Papavassilioua University of Campinas (UNICAMP) "Gleb Wataghin" Institute of Physics 13083-859 Campinas SP Brazil European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT^＊) and Fondazione Bruno Kessler Villa Tambosi Strada delle Tabarelle 286 1-38123 Villazzano (TN) Italy Department of Theoretical Physics and IFIC University of Valencia and CSIC E-46100 Valencia Spain

We present a pedagogical overview of the nonperturbative mechanism that endows gluons with a dynamical mass. This analysis is performed based on pure Yang-Mills theories in the Landau gauge, within the theoretical framework that emerges from the combination of the pinch technique with the background field method. In particular, we concentrate on the Schwinger-Dyson equation satisfied by the gluon propagator and examine the necessary conditions for obtaining finite solutions within the infrared region. The role of seagull diagrams receives particular attention, as do the identities that enforce the cancellation of all potential quadratic divergences. We stress the necessity of introducing nonperturbative massless poles in the fully dressed vertices of the theory in order to trigger the Schwinger mechanism, and explain in detail the instrumental role of these poles in maintaining the Becchi-Rouet-Stora-Tyutin symmetry at every step of the mass-generating procedure. The dynamical equation governing the evolution of the gluon mass is derived, and its solutions are determined numerically following implementation of a set of simplifying assumptions. The obtained mass function is positive definite, and exhibits a power law running that is consistent with general arguments based on the operator product expansion in the ultraviolet region. A possible connection between confinement and the presence of an inflection point in the gluon propagator is briefly discussed.

关键词： nonperturbative physics Schwinger-Dyson equations dynamical mass generation

Valence Quark Ratio in the Proton

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Chinese Physics Letters 2022年第4期39卷 1-6页

作者： Zhu-Fang Cui Fei Gao da.iele binosi Lei Chang Craig D.Roberts Sebastian M.Schmidt School of Physics Nanjing UniversityNanjing 210093China Institute for Nonperturbative Physics Nanjing UniversityNanjing 210093China Centre for High Energy Physics Peking UniversityBeijing 100871China European Centre for Theoretical Studies in Nuclear Physics and Related Areas Villa TambosiStrada delle Tabarelle 286I-38123 Villazzano(TN)Italy School of Physics Nankai UniversityTianjin 300071China Helmholtz-Zentrum Dresden-Rossendorf Dresden D-01314Germany RWTH Aachen University III.Physikalisches Institut BAachen D-52074Germany

Beginning with precise data on the ratio of structure functions in deep inelastic scattering(DIS)from ^3He and ^3H,collected on the domain 0.19≤xB≤0.83,where xBis the Bjorken scaling variable,we employ a robust method for extrapolating such data to arrive at a model-independent result for the xB=1 value of the ratio of neutron and proton structure *** this with information obtained in analyses of DIS from nuclei,corrected for target-structure dependence,we arrive at a prediction for the proton valence-quark ratio:d_(v)/u_(v)|_(xB→1)=0.230(57).Requiring consistency with this result presents a challenge to many descriptions of proton structure.

关键词： structure functions precise

Hadron and light nucleus radii from electron scattering

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Chinese Physics C 2022年第12期46卷 1-15页

作者： Zhu-Fang Cui da.iele binosi Craig D.Roberts Sebastian M.Schmidt School of Physics Nanjing UniversityNanjing 210093China Institute for Nonperturbative Physics Nanjing UniversityNanjing 210093China European Centre for Theoretical Studies in Nuclear Physics and Related Areas Villa Tambosi Strada delle Tabarelle 286I-38123 Villazzano(TN)Italy Helmholtz-Zentrum Dresden-Rossendorf Dresden D-01314Germany RWTH Aachen University Ⅲ.Physikalisches Institut BAachen D-52074Germany

Conceptually,radii are amongst the simplest Poincaré-invariant properties that can be associated with hadrons and light *** values of these quantities are necessary so that one may judge the character of putative solutions to the strong interaction problem within the Standard ***,limiting their ability to serve in this role,recent measurements and new analyses of older data have revealed uncertainties and imprecisions in the radii of the proton,pion,kaon,and *** the context of radius measurement using electron+hadron elastic scattering,the past decade has shown that reliable extraction requires minimisation of bias associated with practitioner-dependent choices of data fitting *** answers to that challenge have been offered;and this perspective describes the statistical Schlessinger point method(SPM),in unifying applications to proton,pion,kaon,and deuteron *** in analytic function theory,independent of assumptions about underlying dynamics,free from practitioner-induced bias,and applicable in the same form to diverse systems and observables,the SPM returns an objective expression of the information contained in any data under *** robust nature and versatility make it suitable for use in many branches of experiment and theory.

关键词： elastic electromagnetic form factors lepton scattering from hadrons and light nuclei emergence of mass muonic atoms proton Nambu-Goldstone modes-pion and kaon deuteron strong interactions in the standard model of particle physics

Drawing insights from pion parton distributions

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Chinese Physics C 2020年第3期44卷 12-17页

作者： Minghui Ding Khépani Raya da.iele binosi Lei Chang C.D.Roberts S.M.Schmidt School of Physics Nankai UniversityTianjin 300071China European Centre for Theoretical Studies in Nuclear Physics and Related Areas(ECT^*)and Fondazione Bruno Kessler Villa Tambosi Strada delle Tabarelle 286I-38123 Villazzano(TN)Italy School of Physics Nanjing UniversityNanjingJiangsu 210093China Institute for Nonperturbative Physics Nanjing UniversityNanjingJiangsu 210093China Institute for Advanced Simulation Forschungszentrum Jülich and JARAD-52425 JülichGermany

A symmetry-preserving continuum approach to the two valence-body bound-state problem is used to calculate the valence, glue and sea distributions within the pion; unifying them with, inter alia, electromagnetic pion elastic and transition form factors. The analysis reveals the following momentum fractions at the scale ζ2:= 2GeV :〈xvalence〉 = 0.48（3）, 〈xglue〉 = 0.41（2）, 〈xsea〉 = 0.11（2）;and despite hardening induced by the emergent phenomenon of dynamical chiral symmetry breaking, the valence-quark distribution function, qπ（x）, exhibits the x ≈ 1 behaviour predicted by quantum chromodynamics（QCD）. After evolution to o ζ = 5.2 GeV, the prediction for qπ（x） matches that obtained using lattice-regularised QCD. This confluence should both stimulate improved analyses of existing data and aid in planning efforts to obtain new data on the pion distribution functions.

关键词： pion parton distribution bound state Dyson-Schwinger equations

Effective charge from lattice QCD

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Chinese Physics C 2020年第8期44卷 23-32页

作者： Z.-F.Cui J.-L.Zhang D.binosi F.De Soto C.Mezrag J.Papavassiliou C.D.Roberts J.Rodríguez-Quintero J.Segovia S.Zafeiropoulos School of Physics Nanjing UniversityNanjing 210093China Institute for Nonperturbative Physics Nanjing UniversityNanjing 210093China Department of Physics Nanjing Normal UniversityNanjing 210023China European Centre for Theoretical Studies in Nuclear Physics and Related Areas Villa TambosiStrada delle Tabarelle 286I-38123 Villazzano(TN)Italy Dpto.Sistemas Físicos Químicos y NaturalesUniv.Pablo de OlavideE-41013 SevillaSpain 6.IRFUCEAUniversitéParis-SaclayF-91191 Gif-sur-YvetteFrance Department of Theoretical Physics and IFIC University of Valencia and CSICE-46100ValenciaSpain Department of Integrated Sciences and Center for Advanced Studies in Physics Mathematics and Computation University of Huelva E-21071 HuelvaSpain Aix Marseille Univ Universitéde ToulonCNRSCPTMarseilleFrance

Using lattice configurations for quantum chromodynamics(QCD)generated with three domain-wall fermions at a physical pion mass,we obtain a parameter-free prediction of QCD’s renormalisation-group-invariant process-independent effective charge,α^(k2).Owing to the dynamical breaking of scale invariance,evident in the emergence of a gluon mass-scale,m0=0.43(1)GeV,this coupling saturates at infrared momenta:α^(0)/π=0.97(4).Amongst other things:α^(k2)is almost identical to the process-dependent(PD)effective charge defined via the Bjorken sum rule;and also that PD charge which,employed in the one-loop evolution equations,delivers agreement between pion parton distribution functions computed at the hadronic scale and *** diversity of unifying roles played byα^(k^2)suggests that it is a strong candidate for that object which represents the interaction strength in QCD at any given momentum scale;and its properties support a conclusion that QCD is a mathematically well-defined quantum field theory in four dimensions.

关键词： running coupling quantum chromodynamics Dyson-Schwinger equations lattice field theory emer-gence of mass confinement