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We present a dispersion theoretical analysis of the experimental data on the electromagnetic form factors of the nucleon covering both the space- and time-like regions. The nucleon form factors over the full range of momentum transfers and…

High Energy Physics - Phenomenology · Physics 2022-02-18 Yong-Hui Lin

In the light of the new data on the various neutron and proton electromagnetic form factors taken in recent years, we update the dispersion-theoretical analysis of the nucleon electromagnetic form factors from the mid-nineties. The…

High Energy Physics - Phenomenology · Physics 2007-05-23 H. -W. Hammer , Ulf-G. Meißner

We review the dispersion-theoretical analysis of the electromagnetic form factors of the nucleon. We emphasize in particular the role of unitarity and analyticity in the construction of the isoscalar and isovector spectral functions. We…

High Energy Physics - Phenomenology · Physics 2021-08-27 Yong-Hui Lin , Hans-Werner Hammer , Ulf-G. Meißner

We update a recent dispersion--theoretical fit to the nucleon electromagnetic form factors by including the existing data in the time--like region. We show that while the time--like data for the proton can be described consistently with the…

High Energy Physics - Phenomenology · Physics 2009-10-28 H. -W. Hammer , Ulf-G. Meißner , D. Drechsel

I discuss how dispersion relations can be used to analyse the nucleon electromagnetic form factors, with particular emphasis on the constraints from unitarity and pQCD. Results for nucleon radii, vector-meson couplings, the onset of pQCD…

High Energy Physics - Phenomenology · Physics 2009-10-30 Ulf-G. Meißner

Dispersion relations provide a powerful tool to describe the electromagnetic form factors of the nucleon both in the spacelike and timelike regions with constraints from unitarity and perturbative QCD. We give a brief introduction into…

High Energy Physics - Phenomenology · Physics 2014-11-17 H. -W. Hammer

The Unitary and analytic model of nucleon electromagnetic structure, describing all existing nucleon form factor data, is briefly reviewed. Then in the framework of this model the problem of inconsistency of older proton electric form…

High Energy Physics - Phenomenology · Physics 2011-08-17 C. Adamuscin , S. Dubnicka , A. Z. Dubnickova , P. Weisenpacher

Elastic electromagnetic form factors of nucleons are investigated both for the time-like and the space-like momentums under the condition that the QCD constraints are satisfied asymptotically. The unsubtracted dispersion relation with the…

High Energy Physics - Phenomenology · Physics 2010-05-12 Susumu Furuichi , Hirohisa Ishikawa , Keiji Watanabe

Elastic electromagnetic form factors of nucleons are investigated both for the time-like and the space-like momentums by using the unsubtracted dispersion relation with QCD constraints. It is shown that the calculated form factors reproduce…

High Energy Physics - Phenomenology · Physics 2010-02-02 Susumu Furuichi , Hirohisa Ishikawa , Keiji Watanbe

For the first time, a phenomenological analysis of the experimental electromagnetic form factors of the nucleon, both in the timelike and spacelike regions, is performed by taking into account the effects of nonvalence components in the…

High Energy Physics - Phenomenology · Physics 2009-02-16 J. P. B. C. de Melo , T. Frederico , E. Pace , S. Pisano , G. Salmè

Dispersion relations allow for a coherent description of the nucleon electromagnetic form factors measured over a large range of momentum transfer, $Q^2 \simeq 0 \ldots 35$ GeV$^2$. Including constraints from unitarity and perturbative QCD,…

High Energy Physics - Phenomenology · Physics 2008-11-26 P. Mergell , Ulf-G. Meißner , D. Drechsel

The electromagnetic form factors $G_{\rm E}$ and $G_{\rm M}$ of the proton and neutron in the timelike region are extracted in a study of the processes $e^+ e^-\to \bar{p}p$ and $e^+ e^-\to \bar{n}n$. The reaction amplitude is evaluated…

Nuclear Theory · Physics 2024-04-22 Qin-He Yang , Di Guo , Ming-Yan Li , Ling-Yun Dai , Johann Haidenbauer , Ulf-G. Meißner

We have made the comparison of three parametrizations of the proton electromagnetic form factors in the space-like region using the largest data set on $e^{\pm} p$ elastic scattering ever used. All models have a correct analytical structure…

High Energy Physics - Phenomenology · Physics 2016-11-23 V. V. Ezhela , B. V. Polishchuk

The electromagnetic form factors of the $\Lambda$ hyperon in the time-like region are determined precisely through a dispersion-theoretical analysis of the world data for the cross section of the annihilation process $e^+e^-\to…

High Energy Physics - Phenomenology · Physics 2022-12-21 Yong-Hui Lin , Hans-Werner Hammer , Ulf-G. Meißner

We present the experimental status of electromagnetic hadron form factors. New and surprising results, based on polarization measurements, have been recently obtained for the electric proton and neutron form factors. In particular, the…

High Energy Physics - Phenomenology · Physics 2015-06-25 Egle Tomasi-Gustafsson

Dispersion relations provide a powerful tool to analyse the electromagnetic form factors of the nucleon for all momentum transfers. Constraints from meson-nucleon scattering data, unitarity, and perturbative QCD can be included in a…

High Energy Physics - Phenomenology · Physics 2008-11-26 M. A. Belushkin , H. -W. Hammer , U. -G. Meißner

An approach for a unified description of the nucleon electromagnetic form factors in spacelike and timelike regions is presented. The main ingredients of our model are: $i)$ a Mandelstam formula for the matrix elements of the nucleon…

High Energy Physics - Phenomenology · Physics 2017-08-23 J. P. B. C. de Melo , T. Frederico , E. Pace , S. Pisano , G. Salme`

Analyticity of nucleon form factors allows to derive sum rules which, using space-like and time-like data as input, can give unique information about behaviors in energy regions not experimentally accessible. Taking advantage from new…

High Energy Physics - Phenomenology · Physics 2011-09-28 S. Pacetti

We present a dispersion theoretical analysis of recent date from electron-proton scattering. This allows for a high-precision extraction of the electric and magnetic radius of the proton, $r_E = (0.839\pm 0.002{}^{+0.002}_{-0.003})$~fm and…

High Energy Physics - Phenomenology · Physics 2022-02-18 Yong-Hui Lin

The electromagnetic form factors of the proton and the neutron in the timelike region are investigated. Electron-positron annihilation into antinucleon-nucleon ($\bar NN$) pairs is treated in distorted wave Born approximation, including the…

Nuclear Theory · Physics 2023-12-06 Qin-He Yang , Ling-Yun Dai , Di Guo , Johann Haidenbauer , Xian-Wei Kang , Ulf-G. Meißner
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