49 research outputs found
Measurement of the neutron timelike electromagnetic form factor with the SND detector
The results of the measurement of the cross section
and effective neutron timelike form factor are presented. The data taking was
carried out in 2020-2021 at the VEPP-2000 collider in the
center-of-mass energy range from 1891 to 2007 MeV. The general purpose
nonmagnetic detector SND is used to detect neutron-antineutron events. The
event selection is performed using the time-of-flight technique. The measured
cross section is 0.4-0.6 nb. The neutron form factor in the energy range under
study varies from 0.3 to 0.2.Comment: 13 pages, 8 figure
Study of the process in the energy range \sqrt{s} = \mbox{1.05-2.00} GeV with the SND detector
The process is studied in the center-of-mass
energy range 1.05-2.00 GeV using data with an integrated luminosity of 94.5
pb collected by the SND detector at the VEPP-2000 collider. The
cross section is measured for the first time. It is
shown that the dominant mechanism of this reaction is the transition through
the intermediate state. The measured cross section of the
subprocess is consistent with previous
measurements in the mode. It is found, with a
significance of 5.6, that the process 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. , is measured. It is found to be
15-20 pb in the wide energy range from 1.3 to 1.9 GeV.Comment: 10 pages, 6 figures, to be submitted to European Physical Journal
Study of the process in the energy range GeV with SND
The process is studied in
the center-of-mass energy region GeV using data with an integral
luminosity of about 35 pb collected with the SND detector at the
VEPP-2000 collider. In the energy range under study, the value of the
measured Born cross section varies from 0.7 to 18 nb. The statistical
uncertainty of the cross section is %, while the systematic uncertainty
is in the range of %. The results are consistent with previous
measurements but have better accuracy.Comment: 13 pages, 11 figure
Study of dynamics of the process in the energy range 1.15--2.00 GeV
The dynamics of the process is studied in the
energy region from 1.15 to 2.00 GeV using data accumulated with the SND
detector at the VEPP-2000 collider. The Dalitz plot distribution and
mass spectrum are analyzed in a model including the intermediate
states , , and . As a result, the
energy dependences of the and cross sections and
the relative phases between the amplitude and the and amplitudes are obtained. The cross section
has a peak in the energy region of the resonance (1.55-1.75
GeV). In this energy range the contributions of the and
states are of the same order of magnitude. No resonance
structure near 1.65 GeV is observed in the cross section. We
conclude that the intermediate state gives a significant
contribution to the decay of , whereas the
mechanism dominates in the decay
.Comment: 9 pages, 7 figures, 3 table
Study of the process in the energy range = 1.07 -- 2 GeV
The cross section is measured in the center-of-mass
energy range from 1.07 to 2.00 GeV in the decay channel ,
. The data set with an integrated luminosity of 242
pb accumulated in the experiment with the SND detector at the VEPP-2000
collider is analyzed.Comment: 12 pages, 3 figures