Meson Form Factors and Deep Exclusive Meson Production Experiments

Horn, T.

doi:10.1051/epjconf/201713705005

Cited by 7 publications

(6 citation statements)

References 52 publications

(48 reference statements)

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“…For example, measuring the pions electromagnetic size and mapping its charge distribution have long been central problems in nuclear physics. The radius is known [6], banner experiments at the Thomas Jefferson National Accelerator Facility (JLab) have provided precise data on the elastic electromagnetic form factor out to Q 2 ≈ 2.5 GeV 2 [42][43][44][45][46], planned experiments will extend this upper bound to Q 2 ≈ 8.5 GeV 2 [47][48][49], and continuum-and lattice-QCD analyses are making predictions that connect these properties to the origin of mass, through the pion's leptonic decay constant and the distribution amplitudes in Fig. 1.…”

Section: Mass Budgetsmentioning

confidence: 99%

Pion and kaon structure at the electron-ion collider

et al. 2019

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Understanding the origin and dynamics of hadron structure and in turn that of atomic nuclei is a central goal of nuclear physics. This challenge entails the questions of how does the roughly 1 GeV mass-scale that characterizes atomic nuclei appear; why does it have the observed value; and, enigmatically, why are the composite Nambu-Goldstone (NG) bosons in quantum chromodynamics (QCD) abnormally light in comparison? In this perspective, we provide an analysis of the mass budget of the pion and proton in QCD; discuss the special role of the kaon, which lies near the boundary between dominance of strong and Higgs mass-generation mechanisms; and explain the need for a coherent effort in QCD phenomenology and continuum calculations, in exa-scale computing as provided by lattice QCD, and in experiments to make progress in understanding the origins of hadron masses and the distribution of that mass within them. We compare the unique capabilities foreseen at the electron-ion collider (EIC) with those at the hadron-electron ring accelerator (HERA), the arXiv:1907.08218v2 [nucl-ex] Rikutaro Yoshida (ryoshida@jlab.org) INTRODUCTIONAtomic nuclei lie at the core of everything we can see; and at the first level of approximation, their atomic weights are simply the sum of the masses of all the neutrons and protons (nucleons) they contain. Each nucleon has a mass m N ∼ 1 GeV, i.e. approximately 2000-times the electron mass. The Higgs boson produces the latter, but what produces the masses of the neutron and proton? This is the crux: the vast majority of the mass of a nucleon is lodged with the energy needed to hold quarks together inside it; and that is supposed to be explained by QCD, the strong-interaction piece within the Standard Model.QCD is unique. It is a fundamental theory with the capacity to sustain massless elementary degrees-of-freedom, viz. gluons and quarks; yet gluons and quarks are predicted to acquire mass dynamically [1][2][3], and nucleons and almost all other hadrons likewise, so that the only massless systems in QCD are its composite NG bosons [4,5], e.g. pions and kaons. Responsible for binding systems as diverse as atomic nuclei and neutron stars, the energy associated with the gluons and quarks within these Nambu-Goldstone (NG) modes is not readily apparent. This is in sharp and fascinating contrast with all other "everyday" hadronic bound states, viz. systems constituted from up = u, down = d, and/or strange = s quarks, which possess nuclear-size masses far in excess of anything that can directly be tied to the Higgs boson. 1

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Section: Mass Budgetsmentioning

confidence: 99%

Pion and kaon structure at the electron-ion collider

et al. 2019

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“…(18). For comparison: an average of computed ρ-meson results tabulated elsewhere [25] yields rρ = 0.67(12) fm, µρ = 2.17 (21), Qρ = −0.55 (28); and using an interaction similar to that defined by Eqs. (10), (11), Ref.…”

Section: A Static Propertiesmentioning

confidence: 99%

“…Electromagnetic form factors should also shed light on the environment sensitivity of phenomena deriving from the emergence of mass. For the pion, despite the experimental challenges, elastic [6][7][8][9][10] and transition [11][12][13][14] form factors have been measured; and the theoretical discussion of these data continues to provide novel insights [15][16][17][18][19][20] and plans for new measurements [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Elastic electromagnetic form factors of vector mesons

Binosi

Cui

et al. 2019

Phys. Rev. D

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A symmetry-preserving approach to the two valence-body continuum bound-state problem is used to calculate the elastic electromagnetic form factors of the ρ-meson and subsequently to study the evolution of vector-meson form factors with current-quark mass. To facilitate a range of additional comparisons, K * form factors are also computed. The analysis reveals that: vector mesons are larger than pseudoscalar mesons; composite vector mesons are non-spherical, with magnetic and quadrupole moments that deviate ∼ 30% from point-particle values; in many ways, vector-meson properties are as much influenced by emergent mass as those of pseudoscalars; and vector meson electric form factors possess a zero at spacelike momentum transfer. Qualitative similarities between the electric form factors of the ρ and the proton, G p E , are used to argue that the character of emergent mass in the Standard Model can force a zero in G p E . Morover, the existence of a zero in vector meson electric form factors entails that a single-pole vector meson dominance model can only be of limited use in estimating properties of off-shell vector mesons, providing poor guidance for systems in which the Higgs-mechanism of mass generation is dominant. *

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“…(1) has yet been claimed. Consequently, experiments planned and approved at the upgraded Jefferson Lab [JLab 12] aim for precision measurements of F π (Q 2 ) to Q 2 = 6 GeV 2 and have the potential to reach Q 2 ≈ 8.5 GeV 2 [14][15][16]. Eq.…”

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confidence: 99%

Mass dependence of pseudoscalar meson elastic form factors

et al. 2018

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A continuum approach to quark-antiquark bound-states is used to determine the electromagnetic form factors of pion-like mesons with masses m 0 − /GeV = 0.14, 0.47, 0.69, 0.83 on a spacelike domain that extends to Q 2 10 GeV 2 . The results enable direct comparisons with contemporary lattice-QCD calculations of heavy-pion form factors at large values of momentum transfer and aid in understanding them. They also reveal, inter alia, that the form factor of the physical pion provides the best opportunity for verification of the factorised hard-scattering formula relevant to this class of exclusive processes and that this capacity diminishes steadily as the meson mass increases. arXiv:1808.09461v1 [nucl-th]

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Meson Form Factors and Deep Exclusive Meson Production Experiments

Cited by 7 publications

References 52 publications

Pion and kaon structure at the electron-ion collider

Pion and kaon structure at the electron-ion collider

Elastic electromagnetic form factors of vector mesons

Mass dependence of pseudoscalar meson elastic form factors

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