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Measurement of the neutron timelike electric and magnetic form factor ratio at the VEPP-2000 $e^{+} e^{-}$ collider

M. N. Achasov^1,2, A. E. Alizzi^1,2, A. Yu. Barnyakov^1,2, E. V. Bedarev^1,2, K. I. Beloborodov^1,2, A. V. Berdyugin^1,2, A. G. Bogdanchikov¹, A. A. Botov¹, T. V. Dimova^1,2 et al.

V. P. Druzhinin^1,2, R. A. Efremov¹, V. N. Zhabin^1,2, V. V. Zhulanov¹, P. V. Zhulanova¹, L. V. Kardapoltsev^1,2, A. S. Kasaev¹, A. A. Kattsin¹, D. P. Kovrizhin¹, I. A. Koop^1,2, A. A. Korol^1,2, A. S. Kupich^1,2, A. P. Kryukov¹, N. A. Melnikova¹, N. Yu. Muchnoi^1,2, A. E. Obrazovsky¹, A. A. Oorzhak^1,2, I. V. Ovtin¹, E. V. Pakhtusova¹, I. A. Polomoshnov¹, K. V. Pugachev^1,2, S. A. Rastigeev¹, Yu. A. Rogovsky^1,2, A. I. Senchenko¹, S. I. Serednyakov ^1,2,*, Z. K. Silagadze ^1,2, K. D. Sungurov^1,2, I. K. Surin¹, Yu. V. Usov¹, A. G. Kharlamov^1,2, D. E. Chistyakov^1,2, and D. A. Shtol¹

¹Budker Institute of Nuclear Physics, SB RAS, Novosibirsk 630090, Russia
²Novosibirsk State University, Novosibirsk 630090, Russia

^*Contact author: S.I.Serednyakov@inp.nsk.su

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Phys. Rev. D 113, 072004 – Published 8 April, 2026

DOI: https://doi.org/10.1103/ynkd-4jzy

Abstract

In the experiment to study the $e^{+} e^{-} \to n \bar{n}$ process at the VEPP-2000 $e^{+} e^{-}$ collider, the ratio $| G_{E} | / | G_{M} |$ of the neutron timelike electric and magnetic form factors has been measured. The experiment was carried out with the SND detector in the center-of-mass energy range 1890–2000 MeV in eight energy points with an integrated luminosity of $83 {pb}^{- 1}$ . The $| G_{E} | / | G_{M} |$ ratio is determined by the analyzing the distribution of the polar angle of the produced antineutron. The measured $| G_{E} | / | G_{M} |$ value in the energy range under study is between 1.0 and 1.5 with an average value of $1.21 \pm 0.13$ .

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Phys. Rev. D 113, 072004– Published 8 April, 2026

Vol. 113, Iss. 7 — 1 April 2026

Received 6 February 2026
Accepted 20 March 2026

DOI: https://doi.org/10.1103/ynkd-4jzy

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Published by the American Physical Society

Physical Review D

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Measurement of the neutron timelike electric and magnetic form factor ratio at the VEPP-2000 $e^{+} e^{-}$ collider

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Measurement of the neutron timelike electric and magnetic form factor ratio at the VEPP-2000 e+e− collider

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Measurement of the neutron timelike electric and magnetic form factor ratio at the VEPP-2000 $e^{+} e^{-}$ collider