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
This paper describes a currently being developed procedure of the charged particle identification for CMD-3 detector, installed at the VEPP-2000 collider. The procedure is based on the application of ...the boosted decision trees classification method, and uses as input variables the specific energy losses of charged particles in the 14 layers of the liquid Xenon calorimeter. The performance of the procedure is demonstrated by an example of the extraction of events of e+e−→K+K−(γ) process in the center of mass energy range from 1.28 to 1.65 GeV.
•The multilayer ionization calorimeter provides multiple dE/dx measurements.•The multiple dE/dx measurements can be used for particle identification.•The set of dE/dx values can be used as input of the boosted decision trees classifier.•The BDT response characterizes the likely type of the particle.•The approach works efficiently for kaon identification at momenta less than 1 GeV/c.
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.
We present a measurement of the pion form factor based on e+e− annihilation data from the CMD-2 detector in the energy range 0.6<s<1.0 GeV with a systematic uncertainty of 0.8%. A data sample is five ...times larger than that used in our previous measurement.
The multi-channel optical readout of a THGEM multiplier coupled to a matrix of 3×3 Geiger-mode APDs (GAPDs) was demonstrated in a two-phase Cryogenic Avalanche Detector (CRAD) in Ar. The GAPDs ...recorded THGEM-hole avalanches in the Near Infrared (NIR) spectral range. At an avalanche charge gain of 160, the yield of the combined THGEM/GAPD-matrix multiplier amounted to ~80 photoelectrons per 20keV X-ray absorbed in the liquid phase. A spatial resolution of 2.5mm (FWHM) has been measured for the impinging X-rays. This technique has potential applications in coherent neutrino-nucleus scattering and in dark matter search experiments.
The process e+e−→K+K−η has been studied in the center-of-mass energy range from 1.59 to 2.007 GeV using the data sample of 59.5 pb−1, collected with the CMD-3 detector at the VEPP-2000 e+e− collider ...in 2011, 2012 and 2017. The K+K−η final state is found to be dominated by the contribution of the ϕ(1020)η intermediate state. The cross section of the process e+e−→ϕ(1020)η has been measured with a systematic uncertainty of 5.1% on the base of 3009 ± 67 selected events. The obtained cross section has been used to calculate the contribution to the anomalous magnetic moment of the muon: aμϕη(E<1.8GeV)=(0.321±0.015stat±0.016syst)×10−10, aμϕη(E<2.0GeV)=(0.440±0.015stat±0.022syst)×10−10. From the cross section approximation the ϕ(1680) meson parameters have been determined with better statistical precision, than in previous studies.
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.
The process e+e−→K+K−π+π− has been studied in the center-of-mass energy range from 1500 to 2000 MeV using a data sample of 23 pb−1 collected with the CMD-3 detector at the VEPP-2000 e+e− collider. ...Using about 24 000 selected events, the e+e−→K+K−π+π− cross section has been measured with a systematic uncertainty decreasing from 11.7% at 1500–1600 MeV to 6.1% above 1800 MeV. A preliminary study of K+K−π+π− production dynamics has been performed.
A study of hadron production at the nucleon-antinucleon threshold has been performed with the CMD-3 detector at the VEPP-2000 e+e− collider. The very fast rise with about 1 MeV width has been ...observed in the e+e−→pp¯ cross section. A sharp drop in the e+e−→3(π+π−) cross section has been confirmed and found to have a less than 2 MeV width, in agreement with the observed fast rise of the e+e−→pp¯ cross section. For the first time a similar sharp drop is demonstrated in the e+e−→K+K−π+π− cross section. The behavior of the e+e−→3(π+π−),K+K−π+π− cross sections cannot be explained by an interference of any resonance amplitude with continuum, therefore this phenomenon cannot be due to a narrow near-threshold resonance. No such structure has been observed in the e+e−→2(π+π−) cross section.