Eur.Phys.J.C 80 (2020) 11, 1008 The process $e^+e^-\to\eta\pi^0\gamma$ is studied in the center-of-mass
energy range 1.05-2.00 GeV using data with an integrated luminosity of 94.5
pb$^{-1}$ collected ...by the SND detector at the VEPP-2000 $e^+e^-$ collider. The
$e^+e^-\to\eta\pi^0\gamma$ cross section is measured for the first time. It is
shown that the dominant mechanism of this reaction is the transition through
the $\omega\eta$ intermediate state. The measured cross section of the
subprocess $e^+e^-\to\omega\eta\to\eta\pi^0\gamma$ is consistent with previous
measurements in the $e^+e^-\to\pi^+\pi^-\pi^0\eta$ mode. It is found, with a
significance of 5.6$\sigma$, that the process $e^+e^-\to\eta\pi^0\gamma$ is not
completely described by hadronic vector-pseudoscalar intermediate states. The
cross section of this missing contribution, which can originate from radiation
processes, e. g. $e^+e^-\to a_{0}(1450)\gamma$, is measured. It is found to be
15-20 pb in the wide energy range from 1.3 to 1.9 GeV.
The cross section of the process \(e^+e^-\to\pi^+\pi^-\) 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 \(\rho\)-resonance region, a systematic uncertainty of 0.7% has been reached. At energies around \(\phi\)-resonance the \(\pi^+\pi^-\) production cross section was measured for the first time with high beam energy resolution. The forward-backward charge asymmetry in the \(\pi^+\pi^-\) 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.
Phys. Rev. D 98, 112001 (2018) The process $e^+e^- \to \pi^0\gamma$ is studied with the SND detector at the
VEPP-2000 $e^+e^-$ collider. Basing on data with an integrated luminosity of 41
pb$^{-1}$ ...recorded in 2010-2012 we measure the $e^+e^- \to \pi^0\gamma$ cross
section in the center-of-mass energy range from 1.075 up to 2 GeV. In the range
1.4-2.0 GeV the process $e^+e^- \to \pi^0\gamma$ is studied for the first time.
JHEP01(2020)112 The cross section of the process $e^{+}e^{-}\rightarrow\eta\pi^{+}\pi^{-}$ 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 $\eta\rightarrow\gamma\gamma$ is used for $\eta$ meson reconstruction in
the data sample corresponding to an integrated luminosity of $78.3$ pb$^{-1}$.
The energy dependence of the $e^{+}e^{-}\rightarrow\eta\pi^{+}\pi^{-}$ cross
section is fitted within the framework of vector meson dominance in order to
extract the
$\Gamma(\rho(1450)\rightarrow{^{+}e^{-}})\mathcal{B}(\rho(1450)\rightarrow\eta\pi^{+}\pi^{-})$
and the
$\Gamma(\rho(1700)\rightarrow{e^{+}e^{-}})\mathcal{B}(\rho(1700)\rightarrow\eta\pi^{+}\pi^{-})$
products. Based on conservation of vector current, the analysed data are used
to test the relationship between the $e^{+}e^{-}\rightarrow\eta\pi^{+}\pi^{-}$
cross section and the spectral function in
$\tau^-\rightarrow\eta\pi^-\pi^0\nu_\tau$ decay. The
$e^{+}e^{-}\rightarrow\eta\pi^{+}\pi^{-}$ cross section measured with the
CMD-$3$ detector is in good agreement with the previous measurements.
Phys. Rev. D 98, 052007 (2018) A search for the rare decay $\eta \rightarrow e^+e^-$ is performed using the
inverse process $e^+e^- \rightarrow \eta$ in the decay mode
$\eta\to\pi^0\pi^0\pi^0 $. We ...analyze data with an integrated luminosity of 654
nb$^{-1} $ accumulated at the VEPP-2000 $e^+e^-$ collider with the SND detector
at the center-of-mass energy $E=m_\eta c ^2\approx 548 $ MeV, and set the upper
limit $ {\cal B} (\eta \rightarrow e^+ e^-) < 7 \times 10^{-7} $ at the 90\%
confidence level.
Phys. Rev. D 97, 032011 (2018) The $e^+e^- \rightarrow K_S K_L \pi^0$ cross section is measured in the
center-of-mass energy range $\sqrt{s}=1.3-2.0$ GeV. The analysis is based on
the data sample ...with an integrated luminosity of 33.5 pb$^{-1}$ collected with
the SND detector at the VEPP-2000 $e^+e^-$ collider.
The process \(e^+e^-\to\eta\eta\gamma\) is studied in the center-of-mass energy range 1.17-2.00 GeV using data with an integrated luminosity of 201 pb\(^{-1}\)collected by the SND detector at the ...VEPP-2000 \(e^+e^-\) collider. The \(e^+e^-\to\eta\eta\gamma\) cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the \(\phi\eta\) intermediate state. Our result on the \(e^+e^-\to\eta\eta\gamma\) cross section is consistent with the \(e^+e^-\to\phi\eta\) measurement in the \(\phi\to K^+ K^-\) mode. The search for radiative processes contributing to the \(e^+e^-\to\eta\eta\gamma\) cross section is performed, and no significant signal is observed.
Phys. Rev. D 94, 112001 (2016) We analyze a 37 pb$^{-1}$ data sample collected with the SND detector at the
VEPP-2000 $e^+e^-$ collider in the center-of-mass energy range 1.05--2.00 GeV
and present ...an updated measurement of the $e^+e^- \to \omega \pi^0 \to
\pi^0\pi^0\gamma$ cross section. In particular, we correct the mistake in
radiative correction calculation made in our previous measurement based on a
part of the data. The measured cross section is fitted with the vector meson
dominance model with three $\rho$-like states and used to test the conserved
vector current hypothesis in the $\tau^-\to\omega\pi^-\nu_{\tau}$ decay.
Phys. Rev. D 94, 092002 (2016) The cross section for the process $e^+e^- \to \omega\eta$ is measured in the
center-of-mass energy range 1.34--2.00 GeV. The analysis is based on data
collected with ...the SND detector at the VEPP-2000 $e^+e^-$ collider. The
measured $e^+e^- \to \omega\eta$ cross section is the most accurate to date. A
significant discrepancy is observed between our data and previous BABAR
measurement.
The dynamics of the process \( e^+e^- \to \pi^+\pi^-\pi^0 \) is studied in the energy region from 1.15 to 2.00 GeV using data accumulated with the SND detector at the VEPP-2000 \(e^+e^-\) collider. ...The Dalitz plot distribution and \(\pi^+\pi^-\) mass spectrum are analyzed in a model including the intermediate states \(\rho(770)\pi\), \(\rho(1450)\pi\), and \(\omega\pi^0\). As a result, the energy dependences of the \(\rho(770)\pi\) and \(\rho(1450)\pi\) cross sections and the relative phases between the \(\rho(770)\pi\) amplitude and the \(\rho(1450)\pi \) and \(\omega\pi^0\) amplitudes are obtained. The \(\rho(1450)\pi\) cross section has a peak in the energy region of the \(\omega(1650)\) resonance (1.55-1.75 GeV). In this energy range the contributions of the \(\rho(770)\pi\) and \(\rho(1450)\pi\) states are of the same order of magnitude. No resonance structure near 1.65 GeV is observed in the \(\rho(770)\pi\) cross section. We conclude that the intermediate state \(\rho(1450)\pi\) gives a significant contribution to the decay of \(\omega (1650)\to\pi^+\pi^-\pi^0\), whereas the \(\rho(770)\pi\) mechanism dominates in the decay \(\omega(1420)\to\pi^+\pi^-\pi^0\).
