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.
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.
The process
is studied in the range of center-of-mass (c.m.) collision energies between 1.05 and 2.00 GeV on the basis of data corresponding to an integrated luminosity of 94.5 pb
that were ...accumulated in an experiment with the SND detector at the VEPP-2000
collider. The cross section for this process was measured for the first time and was found to receive a dominant contribution from the mechanism of a transition through an
intermediate state. The cross section measured for the process
agrees with the results of earlier measurements in the channel
. At a level of 5.7 standard deviations (5.7
), it is established that the process
is not fully described by hadronic intermediate states of the
type. The cross section was measured for this missing contribution, which may be generated by radiative processes—for example,
. It ranges from 15 to 20 pb over a broad energy interval extending from 1.3 to 1.9 GeV.
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.
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.
The beam energy measurement system (BEMS) for the upgraded Beijing electron–positron collider BEPC-II is described. The system is based on measuring the energies of Compton back-scattered photons. ...The relative systematic uncertainty of the electron and positron beam energy determination is estimated as 2×10−5. The relative uncertainty of the beam's energy spread is about 6%.
In an experiment with the SND detector at the VEPP-2000
collider, the cross sections for the processes
and
were measured at collision energies of
GeV in the center-of-mass frame. The results agree ...with the results of earlier measurements in the BABAR experiment and have a commensurate precision.
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.
Energy deviation study of BEMS at BEPCII Zhang, J.Y.; Cai, X.; Mo, X.H. ...
Nuclear physics. B,
February 2019, 2019-02-00, 2019-02-01, Letnik:
939, Številka:
C
Journal Article
Recenzirano
Odprti dostop
The beam energy measurement system (BEMS) at the upgraded Beijing Electron-Positron Collider (BEPCII) is designed to provide beam energy value with the relative error at the level of 5×10−5. The ...obvious energy deviation found during J/ψ resonance scan in 2012 leads to great amount of investigations on both BEPCII and BEMS sides. The reasons causing such an unexpected difference are figured out, which include the neutron damage to HPGe detector, the leakage of RF cavity, and the background from Linac. Based on a series of measures, the ψ(3686) line shape scan is designed and performed, the experimental result indicates that BEMS can measure the beam energy with the claimed accuracy. The afterward performance of BEMS is smooth and stable, and BEMS will play a crucial role in the following high accurate experiments.
Study of the Process in the Energy Range GeV Achasov, M. N.; Barnyakov, A. Yu; Beloborodov, K. I. ...
Physics of atomic nuclei,
2023/12, Letnik:
86, Številka:
6
Journal Article
Recenzirano
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.
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