arXiv subjects
Publications and source records attributed to Z. K. Silagadze.
The current status of experiments with SND detector at VEPP-2M e^+e^- collider in the energy range 2E_0=400-1400 MeV and recent results of data analysis for $ϕ$, $ω$ and $ρ$ decays and e^+e^- annihilation into hadrons are presented.
The process of hard photon emission by initial electrons (positrons) at B-factories is discussed. It is shown that studies of the bottomonium spectroscopy will be feasible for the planned integrated luminosity of the B-factory experiments.
In the experiment with the SND detector at VEPP-2M e^+e^- collider the process $e^+e^-\toπ^+π^-π^0$ was studied in the energy range 2E_0 from 1.04 to 1.38 GeV. A broad peak was observed with the visible mass $M_{vis}=1220\pm 20$ MeV and cross section in the maximum $σ_0\simeq 4$ nb. The peak can be interpreted as a $ω$-like resonance $ω(1200)$.
The Spherical Neutral Detector (SND) operates at VEPP-2M collider in Novosibirsk studying e^+e^- annihilation in the energy range up to 1.4 GeV. Detector consists of a fine granulated spherical scintillation calorimeter with 1632 NaI(Tl) crystals, two cylindrical drift chambers with 10 layers of sense wires, and a muon system made of streamer tubes and plastic scintillation counters. The detector design, performance, data acquisition and processing are described.
Results of the SND experiment at the VEPP-2M e+ e- collider on the QED processes e+ e- --> e+ e- gamma and e+ e- --> e+ e- gamma gamma with production at large angles are presented. Energy and angular distributions of the final particles were studied. No deviations from QED with an accuracy of 3.8% for the first process and 10.3% for the second were found.
Lepton flavor violating decays $Z \to μτ$ and $J/Ψ, Υ\to μτ$ are considered. It is shown that these decays can reach sizeable magnitudes if some specific lepton-flavor violating 4-fermion operators are generated by low scale quantum gravity effects, or by some other new physics at a TeV scale.
SND (Spherical Neutral Detector) is a general purpose nonmagnetic detector, successfully operating at Novosibirsk VEPP-2M collider during last four years in the center of mass energy range from 400 MeV up to 1400 MeV. Its crucial part is a 3-layer, fine grained, spherical NaI(Tl) electromagnetic calorimeter consisted of 1632 individual counters. Here we present a detailed description of the calorimeter and its performance, including such topics as calorimeter design, electronics, calibration, energy and spatial resolutions, particle identification. The calorimeter performance is illustrated by examples from the current studies of different physical processes.
The search for CP-violating K_S\to3π^0 decay was performed with SND detector at VEPP-2M e^+e^- collider. The total amount of data corresponding to 7 million produced K_S mesons was analyzed. No candidate events were found, giving an upper limit of the decay branching ratio: Br(K_S\to3π^0) < 1.4\cdot10^{-5} at 90% confidence level.
The process e^+e^- ->mu^+mu^- has been studied with SND detector at VEPP-2M e^+e^- collider in the vicinity of phi(1020) resonance. The product of branching ratios of phi meson into leptons \sqrt{B(phi->mu^+mu^-) B(phi-> e^+e^-)}=(3.14+-0.22+-0.14)x10^{-4} was measured from the interference in the cross section of the process e^+e^- ->mu^+mu^-. The branching ratio B(phi->mu^+mu^-)=(3.30+-0.45+-0.32)x10^{-4} was obtained.
A curious observation was made that the rank statistics of scientific citation numbers follows Zipf-Mandelbrot's law. The same pow-like behavior is exhibited by some simple random citation models. The observed regularity indicates not so much the peculiar character of the underlying (complex) process, but more likely, than it is usually assumed, its more stochastic nature.
The reaction e^+e^- ---> OMEGA+PI0 ---> PI+PI- 2PI0 has been studied with SND detector at VEPP-2M e^+e^- collider in the vicinity of the PHI(1020) meson resonance. The observed interference pattern in the energy dependence of the cross section is consistent with existence of the decay PHI ---> OMEGA+PI0 with a branching ratio of B(PHI ---> OMEGA+PI0)=(4.8+1.9-1.7+-0.8)x10^{-5}. The real and imaginary parts of the decay amplitude were measured. The PHI ---> OMEGA+PI0 decay was observed for the first time.
In the SND experiment at the VEPP-2M electron-positron collider the PHI(1020)--->PI0+PI0+GAMMA decay was studied. The branching ratio B(PHI--->PI0+PI0+GAMMA)=(1.14+-0.10+-0.12)x10^{-4} was measured. It was shown, that the F0(980)GAMMA mechanism dominates in this decay and the 4-quark model of F0(980) describes our data most consistently.
Short overview of experiments with SND detector at VEPP-2M e^+e^- collider in the energy range 2E = 400 - 1400 MeV and preliminary results of data analysis are presented.
Signal of the rare radiative decay PHI--->ETA+PI0+GAMMA was observed in the SND experiment at VEPP-2M electron-positron collider.The result is based on the analysis of data, corresponding to a total integrated luminosity of 4 pb^{-1}, or 8x10^6 PHI mesons produced. The measured branching ratio of PHI--->ETA+PI0+GAMMA decay is equal to (0.83+-0.23)x10^{-4}.
In the SND experiment at VEPP-2M e^+e^- collider the phi(1020) ---> eta+gamma ---> 3pi^0+gamma decay was studied. The branching ratio B(phi--->eta+gamma) = (1.246 +- 0.025 +- 0.057)% was measured.
Some semileptonic weak decays of vector mesons are considered in the framework of the most popular quark models. The predicted branching ratios are unfortunately too small to make a study of these decays realistic at meson factories under construction.
The existence of the mirror world, with the same microphysics as our own one but with opposite P-asymmetry, not only restores an exact equivalence between left and right but also naturally explains, via a see-saw like mechanism, why the neutrino is ultralight.
Results from the Spherical Nonmagnetic Detector (SND) on $Δ(1232)$ isobar electroproduction in the collisions of beam electrons (positrons) and residual gas nuclei in the VEPP-2M $e^+e^-$ collider are presented. On the basis of the obtained data the expected counting rate of this process in future high luminosity $e^+e^-$ colliders (~$ϕ$-, $c$-$τ$- and $b$-factories) was estimated.