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Constraints on the [Formula: see text] form factor from analyticity and unitarity
Motivated by the discrepancies noted recently between the theoretical calculations of the electromagnetic [Formula: see text] form factor and certain experimental data, we investigate this form factor using analyticity and unitarity in a framework known as the method of unitarity bounds. We use a QC...
Autores principales: | , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Springer Berlin Heidelberg
2014
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4423875/ https://www.ncbi.nlm.nih.gov/pubmed/25983640 http://dx.doi.org/10.1140/epjc/s10052-014-3209-4 |
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author | Ananthanarayan, B. Caprini, I. Kubis, B. |
author_facet | Ananthanarayan, B. Caprini, I. Kubis, B. |
author_sort | Ananthanarayan, B. |
collection | PubMed |
description | Motivated by the discrepancies noted recently between the theoretical calculations of the electromagnetic [Formula: see text] form factor and certain experimental data, we investigate this form factor using analyticity and unitarity in a framework known as the method of unitarity bounds. We use a QCD correlator computed on the spacelike axis by operator product expansion and perturbative QCD as input, and exploit unitarity and the positivity of its spectral function, including the two-pion contribution that can be reliably calculated using high-precision data on the pion form factor. From this information, we derive upper and lower bounds on the modulus of the [Formula: see text] form factor in the elastic region. The results provide a significant check on those obtained with standard dispersion relations, confirming the existence of a disagreement with experimental data in the region around [Formula: see text] . |
format | Online Article Text |
id | pubmed-4423875 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2014 |
publisher | Springer Berlin Heidelberg |
record_format | MEDLINE/PubMed |
spelling | pubmed-44238752015-05-13 Constraints on the [Formula: see text] form factor from analyticity and unitarity Ananthanarayan, B. Caprini, I. Kubis, B. Eur Phys J C Part Fields Regular Article - Theoretical Physics Motivated by the discrepancies noted recently between the theoretical calculations of the electromagnetic [Formula: see text] form factor and certain experimental data, we investigate this form factor using analyticity and unitarity in a framework known as the method of unitarity bounds. We use a QCD correlator computed on the spacelike axis by operator product expansion and perturbative QCD as input, and exploit unitarity and the positivity of its spectral function, including the two-pion contribution that can be reliably calculated using high-precision data on the pion form factor. From this information, we derive upper and lower bounds on the modulus of the [Formula: see text] form factor in the elastic region. The results provide a significant check on those obtained with standard dispersion relations, confirming the existence of a disagreement with experimental data in the region around [Formula: see text] . Springer Berlin Heidelberg 2014-12-17 2014 /pmc/articles/PMC4423875/ /pubmed/25983640 http://dx.doi.org/10.1140/epjc/s10052-014-3209-4 Text en © The Author(s) 2014 https://creativecommons.org/licenses/by/4.0/ Open AccessThis article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited. Funded by SCOAP3 / License Version CC BY 4.0. |
spellingShingle | Regular Article - Theoretical Physics Ananthanarayan, B. Caprini, I. Kubis, B. Constraints on the [Formula: see text] form factor from analyticity and unitarity |
title | Constraints on the [Formula: see text] form factor from analyticity and unitarity |
title_full | Constraints on the [Formula: see text] form factor from analyticity and unitarity |
title_fullStr | Constraints on the [Formula: see text] form factor from analyticity and unitarity |
title_full_unstemmed | Constraints on the [Formula: see text] form factor from analyticity and unitarity |
title_short | Constraints on the [Formula: see text] form factor from analyticity and unitarity |
title_sort | constraints on the [formula: see text] form factor from analyticity and unitarity |
topic | Regular Article - Theoretical Physics |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4423875/ https://www.ncbi.nlm.nih.gov/pubmed/25983640 http://dx.doi.org/10.1140/epjc/s10052-014-3209-4 |
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