Phys. Lett. B 800, 135074 (2020) A search for direct production of the $f_1(1285)$ resonance in $e^+e^-$
annihilation is performed with the SND detector at the VEPP-2000 $e^+e^-$
collider. The ...analysis is based on data with an integrated luminosity of 15.1
pb$^{-1}$ accumulated in the center-of-mass energy range 1.2--1.4 GeV. Two
$e^+e^-\to f_1(1285)$ candidate events are found at the peak of the resonance
and zero events beyond the resonance. The significance of the $e^+e^-\to
f_1(1285)$ signal is $2.5\sigma$. The cross section at the maximum of the
resonance is found to be $\sigma(e^+e^-\to f_1)=45^{+33}_{-24}$ pb. The
corresponding branching fraction $B(f_1(1285)\to
e^+e^-)=(5.1^{+3.7}_{-2.7})\times 10^{-9}$. We consider this result as a first
indication of the process $e^+e^-\to f_1(1285)$. The measured branching
fraction is consistent with the theoretical prediction.
Using the KEDR detector at the VEPP-4M $e^+e^-$ collider, we have determined
the values of $R$ at thirteen points of the center-of-mass energy between 1.84
and 3.05 GeV. The achieved accuracy is ...about or better than $3.9\%$ at most of
the energy points with a systematic uncertainty less than $2.4\%$.
The product of the electronic width of the $\psi(2S)$ meson and the branching
fraction of its decay to the muon pair was measured in the $e^{+}e^{-} \to
\psi(2S) \to \mu^{+}\mu^{-}$ process using ...nine data sets corresponding to an
integrated luminosity of about 6.5 pb$^{-1}$ collected with the KEDR detector
at the VEPP-4M electron-positron collider: \
\Gamma_{ee}\times\mathcal{B}_{\mu\mu} = 19.3 \pm 0.3 \pm 0.5 ~\text{eV}. \
Adding the previous KEDR results on hadronic and leptonic channels, the values
of the $\psi(2S)$ electronic width were obtained under two assumptions: either
with the assumption of lepton universality \ \Gamma_{ee} = 2.279 \pm 0.015 \pm
0.042 ~\text{keV} \ or without it, summing up hadronic and three independent
leptonic channels: \ \Gamma_{ee} = 2.282 \pm 0.015 \pm 0.042 ~\text{keV}. \
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.
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