Experimental study of the $e^+e^-\to n\bar n$ process at the VEPP-2000 $e^+e^-$ collider with the SND detector
/ Authors
M. Achasov, A. Barnyakov, K. Beloborodov, A. Berdyugin, D. Berkaev, A. Bogdanchikov, A. Botov, G. Chizhik, T. Dimova, V. Druzhinin
and 25 more authors
L. Kardapoltsev, A. Kharlamov, V. A. Kladov, I. Koop, A. Korol, D. Kovrizhin, A. Kupich, A. Lysenko, N. Melnikova, N. Muchnoi, A. Obrazovsky, E. Pakhtusova, E. Perevedentsev, K. Pugachev, S. Serednyakov, Z. Silagadze, P. Shatunov, Y. Shatunov, D. Shtol, D. Shwartz, I. Surin, Y. Usov, I. Zemlyansky, V. Zhabin, V. Zhulanov
/ Abstract
The process $e^+e^-\to n\bar n$ is studied in the experiment at the VEPP-2000 $e^+e^-$ collider with the SND detector. The technique of the time measurements in the multichannel NaI(Tl) electromagnetic calorimeter is used to select nnbar events. The value of the measured cross section in the center-of-mass energy range from 1.894 to 2 GeV varies from 0.5 to 0.35 nb. The effective neutron timelike form factor is derived from the measured cross section and compared with the proton form factor. The ratio of the neutron electric and magnetic form factors is obtained from the analysis of the antineutron polar angle distribution and found to be consistent with unity.