The cross section of the process e + e − → π + π − has been measured in the center-of-mass energy range from 0.32 to 1.2 GeV with the CMD-3 detector at the electron-positron collider VEPP-2000. The ...measurement is based on an integrated luminosity of about 88 pb − 1 , of which 62 pb − 1 represent a complete dataset collected by CMD-3 at center-of-mass energies below 1 GeV. In the dominant region near the ρ resonance a systematic uncertainty of 0.7% was achieved. The implications of the presented results for the evaluation of the hadronic contribution to the anomalous magnetic moment of the muon are discussed. Published by the American Physical Society 2024
A
bstract
The cross section of the process
e
+
e
−
→ ηπ
+
π
−
is measured using the data collected with the CMD-3 detector at the VEPP-2000 collider in the center-of-mass energy range from 1
.
1 to 2
....
0 GeV. The decay mode
η → γγ
is used for
η
meson reconstruction in the data sample corresponding to an integrated luminosity of 78
.
3 pb
−
1
. The energy dependence of the
e
+
e
−
→ ηπ
+
π
−
cross section is fitted within the framework of vector meson dominance in order to extract the Γ(
ρ
(1450)
→ e
+
e
−
)
B
(
ρ
(1450)
→ ηπ
+
π
−
) and the Γ(
ρ
(1700)
→ e
+
e
−
)
B
(
ρ
(1700)
→ ηπ
+
π
−
) products. Based on conservation of vector current, the analyzed data are used to test the relationship between the
e
+
e
−
→ ηπ
+
π
−
cross section and the spectral function in
τ
−
→ ηπ
−
π
0
ντ
decay. The
e
+
e
−
→ ηπ
+
π
−
cross section obtained with the CMD-3 detector is in good agreement with the previous measurements.
Antiviral activity of TiO
2
· PL · DNA/PNA nanobiocomposites was studied on the MDCK cell culture infected with influenza A virus (H3N2 subtype). A PNA fragment in nanocomposites was ...electrostatically bound in the form of a DNA/PNA heteroduplex to titanium dioxide nanoparticles precovered with polylysine (TiO
2
· PL). It was shown that TiO
2
· PL · DNA
1
/PNA
1
nanobiocomposite bearing the PNA1 fragment targeted to the 3′-end of the noncoding region of segment 5 of viral RNA specifically inhibited the virus reproduction with an efficiency of 99.8%. The 50% cytotoxic concentration (TC
50
) and 50% effective inhibitory concentration (IC
50
) of the TiO
2
· PL · DNA
1
/PNA
1
nanocomposite were evaluated to be more than 1200 μg/mL and less than 3 μg/mL, respectively. Based on these data, the selectivity index (SI) for TiO
2
· PL · DNA
1
/PNA
1
nanobiocomposite defined as the TC
50
/IC
50
ratio, was calculated to be more than 400. Thus, TiO
2
· PL · DNA/PNA nanobiocomposites were shown to not only penetrate through cell membranes, but exhibit a high specific antisense activity without toxic effects on the living cells.
The paper describes a method of the charged particle identification, developed for the CMD-3 detector, installed at the VEPP-2000 e+e− collider. The method is based on application of boosted decision ...trees classifiers, trained for the optimal separation of electrons, muons, pions and kaons in the momentum range from 100 to 1200MeV/c. The input variables for the classifiers are linear combinations of the energy depositions of charged particles in 12 layers of the liquid xenon calorimeter of the CMD-3. The event samples for training of the classifiers are taken from the simulation. Various issues of the calorimeter strip channels response simulation and their calibration are considered. Application of the method is illustrated by the examples of separation of the e+e−(γ) and π+π−(γ) final states and of selection of the K+K− final state at high energies.
A study was carried out on the photovoltaic and photoconductive properties of fi lm composites of a styrene copolymer with nonyl methacrylate and polyNepoxypropylcarbazole doped with lanthanide ...complexes Ln
2
L
6
·PS (Ln = Nd, Eu, Gd, Yb), HL is the carbacylamidophosphate ligand, CCl
3
C(O)N(H)P(O)(NEt
2
)
2
, N-bis(diethylamino) phosphoryl2,2,2-trichloroacetamide; PS is 3,6-dipyridin-2-yl-1,2,4,5-tetrazine, C
5
H
4
N–C
2
N
4
–C
5
H
4
N). In the visible spectral range, these composites were found to have holetype photoconductivity. The internal photoelectric effect is a function of the photogeneration of charge carriers from the metal complex molecules and the sensitizer. EPR was used to study the kinetics of the formation and relaxation of the photogenerated charge carriers. We conclude that the metal complex molecules in the polymer composite enhance the efficiency of photogeneration of nonequilibrium charge carriers and thereby affect the photovoltaic properties of the composites.
The cross section of the process e + e − → π + π − has been measured in the center of mass energy range from 0.32 to 1.2 GeV with the CMD-3 detector at the electron-positron collider VEPP-2000. The ...measurement is based on a full dataset collected below 1 GeV during three data taking seasons, corresponding to an integrated luminosity of about 62 pb − 1 . In the dominant ρ -resonance region, a systematic uncertainty of 0.7% has been reached. At energies around ϕ -resonance the π + π − production cross section was measured for the first time with high beam energy resolution. The forward-backward charge asymmetry in the π + π − production has also been measured. It shows a strong deviation from the theoretical prediction based on the conventional scalar quantum electrodynamics framework, and it is in good agreement with the generalized vector-meson-dominance and dispersive-based predictions. The impact of the presented results on the evaluation of the hadronic contribution to the anomalous magnetic moment of muon is discussed. Published by the American Physical Society 2024
Photovoltaic and photoconductive properties of styrene–nonyl-methacrylate copolymer and poly(N-epoxypropylcarbazole) film composites doped with the tetranuclear metal complex Cu
4
L
4
(OCH
3
)
4
(L
–
...= N,N′-dibenzyl-N″-trichloroacetyltriamidophosphate) and a sensitizer, i.e., an organic compound with intramolecular charge transfer, were investigated. It was found that these composites had hole-type photoconductivity in the visible spectral range. The internal photoelectric effect was determined by the photogeneration of charge carriers from the metal complex and sensitizer. The kinetics of formation and relaxation of photogenerated charge carriers were studied using ESR. It was concluded that metal-complex molecules in the polymer composite increased the efficiency of photogeneration of nonequilibrium charge carriers and affected the composite photovoltaic properties.
Existing Monte-Carlo generators with radiative corrections to the
e
+
e
-
→π
+
π
-
process are usually developed under the assumption that pions can be treated as pointlike particles. We study the
e
...+
e
-
→π
+
π
-
γ
process with final-state radiation and test this assumption using simulated events from the MCGPJ generator based on the scalar QED hypothesis. In order to increase a fraction of events with FSR, the analysis was performed in the energy region to the left from the
ρ
-meson peak (660÷785 MeV) that is based on the integrated luminosity of about 8.4 pb
-1
. The experimental data for the photon energy spectrum agree with the simulation results at 1% level.
The process e+e−→K+K− has been studied using 1.7×106 events from a data sample corresponding to an integrated luminosity of 5.7 pb−1 collected with the CMD-3 detector in the center-of-mass energy ...range 1010–1060 MeV. The cross section is measured with about 2% systematic uncertainty and is used to calculate the contribution to the anomalous magnetic moment of the muon aμK+K−=(19.33±0.40)×10−10, and to obtain the ϕ(1020) meson parameters. We consider the relationship between the e+e−→K+K− and e+e−→KS0KL0 cross sections and compare it to the theoretical prediction.
A brief review of the recent results on the hadronic cross section measurements with the CMD-3 detector at the
e
+
e
−
collider VEPP-2000 is given. Focus is made on the processes with charged kaons ...in multihadron events, which have a strong impact on strange meson spectroscopy and form factors that are important ingredients in the Dalitz plot analysis. Experimental data relevant to the topic are presented from the broad energy range covered by VEPP-2000 and compared to earlier measurements by the different collaborations. The analysis is based on the integrated luminosity of about 100 pb
−1
collected in 2011, 2012 and 2017.
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