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
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.
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
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
The research investigates the structure of a welded joint of a railway rail after local heat treatment and without it. Macro- and microstructural analyses of rail samples were performed using optical ...microscopy methods. The hardness of the rail running surface in the heat-affected zone of butt welds was measured. It has been found that the formation of zones with reduced hardness is inevitable due to the temperature gradient created during the welding process. Moreover, using local induction heat treatment results in the formation of new, more extended zones with reduced hardness. It has been determined that the only solution to this problem is to reduce the extent of heat-affected zones to sizes that do not lead to increased wear and local crushing.
The main principles of using wires with tungsten nanopowder for arc cladding are considered. Special features of production and application of tungsten-modified wires are analyzed. The microstructure ...of the high-strength layer obtained by cladding wires with different tungsten nanopowder contents is investigated. Microhardness of clad specimens is determined.
Surfaced layers formed by arc cladding of powder wires produced by the Siberian State Industrial University and used for surfacing articles operating under abrasive wear are studied. The chemical ...composition, the microstructure and the hardness of the deposited layers and of the nonmetallic inclusions formed in them are analyzed. Titanium addition in the wires is shown to affect positively the wear resistance of the layers.
Microstructural parameters of clad metal from Fe – C – Si – Mn – Cr – Ni – Mo – Vpowder wire with an addition containing carbon and fluorine cleaning dust of aluminum production instead of amorphous ...carbon are determined. The chemical composition and the microstructural parameters including the grain diameter, the interlamellar distance, the type of the structure of the deposited layer and its chemical composition are determined.
The physicochemical basis for the formation of deposits on equipment in petroleum and natural gas processing plants has been examined. Feasibility was established for the use of magnetic methods in ...the petroleum and natural gas industry for extraction, transport, storage, and processing of the hydrocarbon feedstock resulting in a change in the dispersion of oil systems in combination with various other procedures. We have attempted to expand our understanding of the mechanism of formation of deposits at high, moderate, and low temperatures over time, especially during magnetic treatment of complex polydisperse hydrocarbon systems.
The article presents the results of studies of the structure and non-metallic inclusions of metal surfaced from a flux-cored wire of the Fe – C – Si – Mn – Cr – Ni – Mo – V system. In the composition ...of the wire charge, instead of amorphous carbon, gas cleaning dust of aluminum production containing carbon and fluorine was introduced. Surfacing from a flux-cored wire with a diameter of 5 mm on plates made of St3 steel under AN-26S flux was carried out using a welding machine at a current of 420 – 520 A, a voltage of 28 – 32 V, a welding rate of 7.2 – 9 m/h with cooling at room temperature. The properties of two samples with different content of the carbon-fluorine-containing additive in a flux-cored wire have been studied. The grain size and martensite dispersion in the structure of the surfaced layer have been determined. The analysis of the chemical composition of the surfaced layer and non-metallic inclusions generated in it has been carried out. The hardness of the samples has been measured by the Rockwell method. It has been concluded that it is necessary to establish the optimal amount of the carbon-fluorine-containing additive in the flux-cored wire in order to avoid the formation of an increased amount of non-metallic inclusions in the surfaced layer.
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