A sensitivity of the VEPP-2000 \(e^+e^-\) collider in a search for the rare decay \(\eta \rightarrow e^+ e^-\) has been studied. The inverse reaction \(e^+ e^- \rightarrow \eta\) is proposed for this ...search. We have analyzed a data sample with an integrated luminosity of 108 nb\(^{-1}\) collected with the SND detector in the center-of-mass energy range 520-580 MeV and found no background events for the reaction \(e^+ e^- \rightarrow \eta\) in the decay mode \(\eta\to\pi^0\pi^0\pi^0\). In the absence of background, a sensitivity to \({\cal B}(\eta \rightarrow e^+ e^-)\) of \(10^{-6}\) can be reached during two weeks of VEPP-2000 operation. Such a sensitivity is better than the current upper limit on \({\cal B}(\eta \rightarrow e^+ e^-)\) by a factor of 2.3.
A search for the process \(e^+e^- \to \eta^\prime\) has been performed with the SND detector at the VEPP-2000 \(e^+e^-\) collider. The data were accumulated at the center-of-mass energy of ...\(957.78\pm 0.06\) MeV with an integrated luminosity of about 2.9 pb\(^{-1}\). For reconstruction of the \(\eta^\prime\) meson five decay chains have been used: \(\eta^{\prime}\to\eta\pi^+\pi^-\) followed by the \(\eta\) decays to \(\gamma\gamma\) and \(3\pi^0 \), and \(\eta^{\prime} \to \eta\pi^0\pi^0\) followed by the \(\eta\) decays to \(\pi^+\pi^-\pi^0\), \(\gamma\gamma\), and \(3\pi^0\). As a result, the upper limit has been set on the \(\eta^\prime\) electronic width: \(\Gamma_{\eta^{\prime}\to e^+e^-} < 0.0020\) eV at the 90\% confidence level.
In the experiment with the SND detector at the VEPP-2000 \(e^+e^-\) collider the cross section for the process \(e^+e^-\to\eta\pi^+\pi^-\) has been measured in the center-of-mass energy range from ...1.22 to 2.00 GeV. Obtained results are in agreement with previous measurements and have better accuracy. The energy dependence of the \(e^+e^-\to\eta\pi^+\pi^-\) cross section has been fitted with the vector-meson dominance model. From this fit the product of the branching fractions \(B(\rho(1450)\to\eta\pi^+\pi^-)B(\rho(1450)\to e^+e^-)\) has been extracted and compared with the same products for \(\rho(1450)\to\omega\pi^0\) and \(\rho(1450)\to\pi^+\pi^-\) decays. The obtained cross section data have been also used to test the conservation of vector current hypothesis.
The process \(e^+e^-\to n\bar{n}\) has been studied at the VEPP-2000 \(e^+e^-\) collider with the SND detector in the energy range from threshold up to 2 GeV. As a result of the experiment, the ...\(e^+e^-\to n\bar{n}\) cross section and effective neutron form factor have been measured.
The article discusses the results of surgical treatment of patients suffering from ischemic heart disease with extensive cicatricial affections of the myocardium and circulatory insufficiency. ...Thirteen patients of group I were treated by various reconstructive operations (resection of an aneurysm, formation of an aortocoronary shunt, septoplasty), 10 patients of group 2 underwent orthotopic heart transplantation. Perioperative and long-term (up to 3 years) mortality rates were, respectively, 7.6 and 8% in group I and, respectively, 30% and zero in group 2. The unfavorable prognosis of survival and medicamentous therapy in such patients, the lack of donors, and the acceptable results of reconstructive operations are evidence that they should be undertaken whenever possible. The main criteria of the selection of patients for a reconstructive operation are the values of regional contractility of the left ventricle, the severity of the dystrophic processes in the preserved segments, and the condition of the coronary arteries.
