Title: Pion off-shell electromagnetic form factors: Data extraction and model analysis

Abstract

We investigate the pion electromagnetic half-off-shell form factors, which parametrize the matrix element of the charged pion electromagnetic current with one leg off mass shell and the other leg on mass shell, using an exactly solvable manifestly covariant model of a (3 + 1)-dimensional fermion field theory. The model provides a three-dimensional imaging of the two off-shell pion form factors $$F_1$$ and $$F_2$$ as a function of ($Q^2, t$), which are related to each other, satisfying the Ward-Takahashi identity. The normalization of the renormalized charge form factor $$F_1$$ is fixed by $$F_1$$ ($$Q^2 = 0 , t = m^2_ π)$$ = 1, while the other form factor $$F_2$$ vanishes; i.e., $$F_2 (Q^2, t = m^2_π$$) = 0 for any value of $Q^2$ due to the time-reversal invariance of the strong interaction. We define the new form factor $$g(Q^ 2, t) = F_2(Q^2, t)/(t – m^2_π)$$ and find that $g(Q^2, t)$ can be measurable in the on-mass-shell limit. In particular, $$g(Q^2 = 0, t = m^2_π)$$ is related with the pion charge radius. We also compare our form factors with the data extracted from the pion electroproduction reaction for both the off-shell region ($$\mathcal{t}$$ < 0) and the on-shell limit ($$t → m^2_ π$$).

Authors:

Choi, Ho-Meoyng ;

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Frederico, T. ;

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Ji, Chueng-Ryong ;

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• Search DOE PAGES for ORCID "0000-0002-3024-5186"
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de Melo, J. P. B. C.

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• Search DOE PAGES for ORCID "0000-0003-1551-9609"
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Publication Date:

2019-12-23

Research Org.:

North Carolina State Univ., Raleigh, NC (United States); Univ. of California, Oakland, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)

Sponsoring Org.:

USDOE Office of Science (SC); National Research Foundation of Korea (NRF); Coordination for the Improvement of Higher Education Personnel (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP)

OSTI Identifier:

1580179

Alternate Identifier(s):

OSTI ID: 1800101

Grant/Contract Number:  

FG02-03ER41260; AC02-05CH11231; NRF-2017R1D1A1B03033129; 308025/2015-6; 308486/2015-3; PVE 401322/2014-9

Resource Type:

Published Article

Journal Name:

Physical Review D

Additional Journal Information:

Journal Name: Physical Review D Journal Volume: 100 Journal Issue: 11; Journal ID: ISSN 2470-0010

Publisher:

American Physical Society

Country of Publication:

United States

Language:

English

Subject:

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Astronomy & Astrophysics; Physics