In the experiment with the SND detector at the VEPP-2000
collider, events of the process
were separated via measuring, in each counter of the multichannel calorimeter based on 1640 NaI(Tl) crystals, ...the time of delay of the signal from nonrelativistic antineutrons. The time resolution for events of the process
was 0.8 ns. The measured time spectrum of delays of the signal from antineutrons in the calorimeter at the c.m. energy of 1902 MeV agrees with the results of calculations.
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The process
was studied in the energy range between 1 and 2 GeV to the best precision in the world. The data used correspond to an integrated luminosity of
accumulated with the SND detector at the ...VEPP-2000
collider. The statistical accuracy of the measured cross section is 2 to 22
, whereas the systematic uncertainty is 2.6 to 14
. The present results agree with the results of earlier measurements but have a better precision.
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Using the SND detector, the process
was studied in the energy range between 1.05 and 2.00 GeV. The respective measurement was performed on the basis of data accumulated in the experiments at the ...VEPP-2000 electron–positron collider throughout the runs of 2011 and 2012. Also, the invariant-mass spectra of the
and
combinations were analyzed in the energy range between 1.15 and 2 GeV. This resulted in finding an indication that the
excited state decayed predominantly through the
intermediate state.
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24.
Status of laser polarimeter at VEPP-4M Blinov, V.E.; Bedareva, T.V.; Zakharov, S.A. ...
Journal of instrumentation,
08/2020, Volume:
15, Issue:
8
Journal Article
Peer reviewed
Laser polarimeter facility at VEPP-4M accelerator is designed to calibrate the beam energy by resonance depolarization method in the energy region of the Υ-meson. The laser trigger and laser ...polarization control system has been upgraded. A new water-cooled vacuum mirror is being developed.
The e+e−→ηπ+π− cross section is measured at the Spherical Neutral Detector (SND) detector in the η decay mode η→3π0. The analysis is based on the data sample with an integrated luminosity of 32.7 ...pb−1 collected at the VEPP-2000 e+e− collider in the center-of-mass energy range s=1.075–2.000 GeV. The data obtained in the η→3π0 decay mode are found to be in agreement with the previous SND measurements in the η→γγ mode. Therefore the measurements in the two modes are combined.
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Data analysis of an experiment in which photon splitting in atomic fields was observed is presented. The experiment was performed at the tagged photon beam of the ROKK-1M facility at the VEPP-4M ...collider. In the energy region of 120-450 MeV, statistics of 1.6x10(9) photons incident on the BGO target was collected. About 400 candidate photon-splitting events were reconstructed. Within the attained experimental accuracy, the experimental results are consistent with the calculated exact atomic-field cross section. The predictions obtained in the Born approximation differ significantly from the experimental results.
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The backscattering of laser radiation by a relativistic electron beam is a widely used method for measuring the spin polarization of electrons. We consider again the properties of the scattering ...process paying special attention to recoil electrons. Based on this consideration we propose the concept of the Compton polarimeter in which, in addition to all the polarization components, it becomes possible to accurately measure the energy and other parameters of the electron beam. To demonstrate the capabilities of the method we conduct a Monte Carlo simulations of the polarimeter developed for the FCC-ee project.
Abstract
The process
$$e^+e^-\rightarrow n{\bar{n}}$$
e
+
e
-
→
n
n
¯
is studied in the experiment at the VEPP-2000
$$e^+e^-$$
e
+
e
-
collider with the SND detector. The technique of the time ...measurements in the multichannel NaI(Tl) electromagnetic calorimeter is used to select
$$n{\bar{n}}$$
n
n
¯
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.
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