Radiative decays of ρ and ω mesons

The results of the measurements of radiative decays of ρ and ω mesons with the Neutral Detector at thee ⁺ e ^? collider VEPP-2M are presented. The branching ratio of the decay ω→π ⁰γ was measured with higher than in previous experiments accuracy: $${\rm B}(\omega \to \pi ^0 \gamma ) = 0.0888 \pm 0.0062$$ . The ρ⁰→π ⁰ γ branching ratio was measured for the first time: $$B(\rho ^0 \to \pi ^0 \gamma ) = (7.9 \pm 2.0) \cdot 10^{ - 4} $$ . The decays ρ, ω→ηγ were studied. Their branching ratios with the assumption of constructive ρ?ω interference are: $$\begin{gathered} B(\omega \to \eta \gamma ) = (7.3 \pm 2.9) \cdot 10^{ - 4} , \hfill \\ B(\rho \to \eta \gamma ) = (4.0 \pm 1.1) \cdot 10^{ - 4} \hfill \\ \end{gathered} $$ . The branching ratios of ρ, ω→ηγ and ω→e ⁺ e ^? decays were also measured: $$\begin{gathered} B(\omega \to \pi ^ + \pi ^ - \pi ^0 ) = 0.8942 \pm 0.0062, \hfill \\ B(\omega \to e^ + e^ - ) = (7.14 \pm 0.36) \cdot 10^{ - 5} \hfill \\ \end{gathered} $$ . The upper limit for the ω→π ⁰ π ⁰ γ branching ratio was placed: B(ω→π ⁰ π ⁰ γ)<4·10^?4 at 90% confidence level.     

Coordination of N-Substituted Porphyrins with Simple and Chelate Zinc Salts in DMSO

The effect of peripheral substitution in the porphyrin macrocycle (₂OEtP, H₂TPP) of the nature of the N-substituent (X = Me, Ph) and of the anion in the salt solvate (A = ^–, NO₃ ^–, ^–) on the complexation of the N-substituted porphyrins with zinc salts in DMSO is studied. The positions of the bands in the electronic absorption spectrum of the (A)M(N-X)P metal complex were found to depend only slightly on the nature of the A anion in the composition of the coordination sphere of the complex. An inhibition of coordination of the N-substituted ₂TPP derivatives by zinc nitrate was discovered that is not typical of porphyrins proper. The type of hybridization of the substituted nitrogen atom in the porphyrin molecule is discussed. A mixed type of hybridization is suggested: the sp ²- and p ³-forms in the ligands and an almost complete transition to the p ³ form in the N-substituted metal complexes.     

Measurement of the relative probability of the decay φ → η′γ in the channel η′ → ηπ0π0, η → γγ

The process e ⁺ e ^? → η′γ, η′ → η π⁰π⁰, η → γγ is investigated by an SND detector in experiment on a VEPP-2M equipment with colliding electron-positron beams. The analysis of experimental data yields a value of B(? → η′γ)=(6.7 _?4.2 ^+5.0 ±1.5)×10^?5 for the decay probability. Taking into account a previous measurement of this quantity by an SND detector in the decay channel η′ → π⁺π^?η, one finally obtains B(?→η ′γ)=(6.7 _?2.4 ^+2.8 ±0.8)×10^?5.     

The VEPP-2000 electron-positron collider: First experiments

In 2007, at the Institute of Nuclear Physics (Novosibirsk), the construction of the VEPP-2000 electron-positron collider was completed. The first electron beam was injected into the accelerator structure with turned-off solenoids of the final focus. This mode was used to tune all subsystems of the facility and to train the vacuum chamber using synchrotron radiation at electron currents of up to 150 mA. The VEPP-2000 structure with small beta functions and partially turned-on solenoids was used for the first testing of the “round beams” scheme at an energy of 508 MeV. Beam-beam effects were studied in strong-weak and strong-strong modes. Measurements of the beam sizes in both cases showed a dependence corresponding to model predictions for round colliding beams. Using a modernized SND (spherical neutral detector), the first energy calibration of the VEPP-2000 collider was performed by measuring the excitation curve of the phimeson resonance; the phi-meson mass is known with high accuracy from previous experiments at VEEP-2M. In October 2009, a KMD-3 (cryogenic magnetic detector) was installed at the VEPP-2000 facility, and the physics program with both the SND and LMD-3 particle detectors was started in the energy range of 1–1.9 GeV. This first experimental season was completed in summer 2010 with precision energy calibration by resonant depolarization.     

Polarized beams at storage rings

This paper reviews modern techniques to accelerate polarized particles to high energy and to preserve their polarization in the storage rings. Possibilities of the bean polarization control are discussed for proton and electron machines.     

Searching for the process e+e- → K+K-π0 in experiments with the spherical neutral detector at VEPP-2M

We have searched for the process e⁺e^- → K⁺K^-π⁰ at energies up to 1.38 GeVin an experiment with the spherical neutral detector at the VEPP-2M e⁺e^- collider. The upper limits of the cross sections for the processes σ(e⁺e →; φπ: → K⁺K^-π⁰) < 0.023 nb and σ(e⁺e^- → KK*(892) → K⁺K^-π⁰) < 0.059 nb have been established at a 95% confidence level.     

Strategies for Probing P-Parity Violation in Nuclear Collisions at the NICA Accelerator Facility

Physics of Particles and Nuclei Letters - Possible approaches to experimentally detecting P-parity violation in polarized proton or deuteron interactions with an unpolarized target are discussed....     

Preliminary results of the cross-section measurement of e<Superscript>+</Superscript>e<Superscript>−</Superscript> → φ(1020)η process with the CMD-3 detector at VEPP-2000 collider

We report preliminary results on the cross section of the process e⁺e^? → φ(1020)η measured at 30 center-of-mass energy points in the range from 1.59 up to 2.0 GeV. Data analysis is based on the integrated luminosity of 22 pb^?1 collected with the CMD-3 detector in 2011–2012. The obtained cross section agrees with the BaBar measurement and has better statistical accuracy.     

Measurement of the e + e − → ηπ+π− cross section in the \sqrt s = 1.04–1.38-GeV energy range with a spherical neutral detector at the VEPP-2M collider

The e ⁺ e ^? → ηπ⁺π^? cross section in the η → 2γ channel has been measured in the $ \sqrt s $ = 1.04- to 1.38-GeV energy range. The data with a total integrated luminosity of 9.05 pb^?1 were collected on a spherical neutral detector at the VEPP-2M collider. The results are consistent with the BaBar and CMD2 data and have a higher statistical accuracy.     

Experimental study of the reaction e + e − → K S K L in the energy range √S = 1.04−1.38 GeV

We present a measurement of the e ⁺ e ⁻ → K _S K _L cross section in the energy range √s = 1.04−1.38 GeV. For an energy of √s ≥ 1.2 GeV the cross section exceeds vector meson dominance model predictions with only ρ(770), ω(783), and ϕ(1020) mesons taken into account. The measured cross section agrees well with previous measurements. Published in Russian in Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2006, Vol. 130, No. 5, pp. 831–839. This article was translated by the authors.