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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Abstract
The process
$$e^+e^-\rightarrow \eta \eta \gamma $$
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
$$^{-1}$$
-
...1
collected by the SND detector at the VEPP-2000
$$e^+e^-$$
e
+
e
-
collider. The
$$e^+e^-\rightarrow \eta \eta \gamma $$
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
$$\phi \eta $$
ϕ
η
intermediate state. Our result on the
$$e^+e^-\rightarrow \eta \eta \gamma $$
e
+
e
-
→
η
η
γ
cross section is consistent with the
$$e^+e^-\rightarrow \phi \eta $$
e
+
e
-
→
ϕ
η
measurement in the
$$\phi \rightarrow K^+ K^-$$
ϕ
→
K
+
K
-
mode. The search for radiative processes contributing to the
$$e^+e^-\rightarrow \eta \eta \gamma $$
e
+
e
-
→
η
η
γ
cross section is performed, and no significant signal is observed.
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Abstract The process $$e^+e^-\rightarrow \eta \eta \gamma $$ 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 $$^{-1}$$ - ...1 collected by the SND detector at the VEPP-2000 $$e^+e^-$$ e + e - collider. The $$e^+e^-\rightarrow \eta \eta \gamma $$ 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 $$\phi \eta $$ ϕ η intermediate state. Our result on the $$e^+e^-\rightarrow \eta \eta \gamma $$ e + e - → η η γ cross section is consistent with the $$e^+e^-\rightarrow \phi \eta $$ e + e - → ϕ η measurement in the $$\phi \rightarrow K^+ K^-$$ ϕ → K + K - mode. The search for radiative processes contributing to the $$e^+e^-\rightarrow \eta \eta \gamma $$ e + e - → η η γ cross section is performed, and no significant signal is observed.
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The cross sections , , , , K+K−, , , have been measured with the spherical neutral detector at the VEPP-2000 e+e− collider in the energy range from 0.3 to 2.0 GeV.
This paper reports measurements of the hadronic cross sections with the CMD-3 detector at the VEPP-2000 electron-positron collider. The overall size of the data sample analyzed is about 60 pb-1, ...collected by the CMD- 3 running since December 2010 up to June 2013 in the c.m. energy range from 0.32 to 2.0 GeV. The preliminary results of data analysis for various modes of e+e−→hadrons are discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A
bstract
The cross section of the process
e
+
e
−
→
π
+
π
−
has been measured in the Spherical Neutral Detector (SND) experiment at the VEPP-2000
e
+
e
−
collider VEPP-2000 in the energy region 525
...<
$$ \sqrt{s} $$
s
<
883 MeV. The measurement is based on data with an integrated luminosity of about 4.6 pb
−
1
. The systematic uncertainty of the cross section determination is 0.8% at
$$ \sqrt{s} $$
s
>
0
.
600 GeV. The
ρ
meson parameters are obtained as
m
ρ
= 775
.
3 ± 0
.
5 ± 0
.
6 MeV, Γ
ρ
= 145
.
6 ± 0
.
6 ± 0
.
8 MeV,
B
ρ
→
e
+
e−
×
B
ρ
→
π
+
π−
= (4
.
89 ± 0
.
02 ± 0
.
04) × 10
−
5
, and the parameters of the
e
+
e
−
→
ω
→
π
+
π
−
process, suppressed by
G
-parity, as
B
ω
→
e
+
e−
×
B
ω
→
π
+
π−
= (1
.
32 ± 0
.
06 ± 0
.
02) × 10
−
6
and and
ϕ
ρω
= 110
.
7 ± 1
.
5 ± 1
.
0 degrees.
CMD-3 Overview Logashenko, Ivan B.; Ignatov, F.V.; Akhmetshin, R.R. ...
EPJ Web of Conferences,
2019, Volume:
218
Journal Article, Conference Proceeding
Peer reviewed
Open access
The CMD-3 detector is installed at the VEPP-2000
e
+
e
−
collider at BINP (Novosibirsk, Russia). It is a general-purpose detector, equipped with a tracking system, two crystal (CSI and BGO) ...calorimeters, liquid Xe calorimeter, TOF and muon systems. The main goal of experiments at CMD-3 is a study of exclusive modes of
e
+
e
−
→
hadrons
at energies $ \sqrt s \le $ GeV. In particular, these results provide an important input for calculation of the hadronic contribution to the muon anomalous magnetic moment.
The first round of data taking was performed in 2011–2013, when about 60 1/pb were taken in the center-of-mass (c.m.) energy range from 0.32 to 2.0 GeV. Here we present a survey of results of data analysis.
Between 2013 and 2016 the collider and the detector were upgraded. The data taking resumed by the end of 2016. In the first run after the upgrade about 50 1/pb were collected at the energy range between 1.28 and 2.007 GeV. We discuss the upgrade and the first preliminary results from the new data.
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The CMD-3 detector has been successfully collecting data at the electron-positron collider VEPP-2000 since December 2010. The first scan below 1 GeV for a π
+
π
−
measurement was performed in 2013. ...The collected data sample corresponds to about 18 pb
−1
of integrated luminosity in this energy range. Analysis of the
e
+
e
−
→ π
+
π
−
cross section is in progress. Status of this measurement are presented.
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The CMD-3 detector started data taking at the electron-positron collider VEPP-2000 1 in December 2010. The collected data sample corresponds to an integrated luminosity of 87 pb
−1
in the c.m. energy ...range from 1.06 up to 2 GeV and 91 pb
−1
from 0.32 to 1.06 GeV. The integrated luminosity was measured by counting
e
+
e
−
→
e
+
e
−
and
e
+
e
−
→ γγ events, allowing additional photons in the final state. Preliminary results of the luminosity measurement are presented for various energy ranges and its accuracy is estimated to be 1%.
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