Search

Results are presented from measuring the cross section and effective neutron timelike form factor. Data are collected in 2020–2021 at the VEPP-2000 collider in the 1891 to 2007 MeV center-of-mass range of energies. The general purpose nonmagnetic SND detector is used to detect neutron–antineutron events. The time-of-flight approach is used to select events. The measured cross section is 0.4–0.6 nbn. The neutron form factor in the investigated range of energies varies from 0.3 to 0.2. [ABSTRACT FROM AUTHOR]

The process e + e - → η η γ is studied in the center-of-mass energy range 1.17–2.00 GeV using data with an integrated luminosity of 201 pb - 1 collected by the SND detector at the VEPP-2000 e + e - collider. The e + e - → η η γ cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the ϕ η intermediate state. Our result on the e + e - → η η γ cross section is consistent with the e + e - → ϕ η measurement in the ϕ → K + K - mode. The search for radiative processes contributing to the e + e - → η η γ cross section is performed, and no significant signal is observed. [ABSTRACT FROM AUTHOR]

The process e + e - → η π 0 γ is studied in the center-of-mass energy range 1.05–2.00 GeV using data with an integrated luminosity of 94.5 pb - 1 collected by the SND detector at the VEPP-2000 e + e - collider. The e + e - → η π 0 γ cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the ω η intermediate state. The measured cross section of the subprocess e + e - → ω η → η π 0 γ is consistent with previous measurements in the e + e - → π + π - π 0 η mode. It is found, with a significance of 5.6 σ , that the process e + e - → η π 0 γ is not completely described by hadronic vector-pseudoscalar intermediate states. The cross section of this missing contribution, which can originate from radiation processes, e. g. e + e - → a 0 (1450) γ , is measured. It is found to be 15–20 pb in the wide energy range from 1.3 to 1.9 GeV. [ABSTRACT FROM AUTHOR]

The results of searches for the process in an experiment with the SND detector at the VEPP-2000 electron–positron collider are presented. The data used in these searches and based on an integrated luminosity of about 87 pb were accumulated at c.m. energies between 1.15 and 2 GeV. The upper limits of pb for GeV and pb for GeV were set at a 90 confidence level. [ABSTRACT FROM AUTHOR]