Leonid Kardapoltsev

The process e+e−→n¯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−→n¯n cross section and effective neutron form factor have been measured.3 MoreReceived 15 October 2014DOI:https://doi.org/10.1103/PhysRevD.90.112007© 2014 American Physical Society

The cross section for the process e + e -→ ωπ 0 → π 0 π 0 γ has been measured in the center-of-mass energy range 1.05-2.00GeV.The experiment has been performed at the e + e -collider VEPP-2000 with the SND detector.The measured e + e -→ ωπ 0 cross section above 1.4 GeV is the most accurate to date.Below 1.4 GeV our data are in good agreement with the previous SND and CMD-2 measurements.Data on the e + e -→ ωπ 0 cross section are well described by the Vector Meson Dominance (VMD) model with two excited ρ-like states.From the measured cross section we have extracted the γ * → ωπ 0 transition form factor.It has been found that the VMD model cannot describe simultaneously our data and data obtained from the ω → π 0 µ + µ -decay.We have also tested Conserved Vector Current (CVC) hypothesis comparing our results on the e + e -→ ωπ 0 cross section with data on the τ -→ ωπ -ντ decay and have found that the CVC hypothesis works well within reached experimental accuracy of about 5%.

In the experiment with the SND detector at the VEPP-2000 ${e}^{+}{e}^{\ensuremath{-}}$ collider the cross section for the process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\eta}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ 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 ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\eta}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ cross section has been fitted with the vector-meson dominance model. From this fit the product of the branching fractions $B(\ensuremath{\rho}(1450)\ensuremath{\rightarrow}\ensuremath{\eta}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})B(\ensuremath{\rho}(1450)\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}})$ has been extracted and compared with the same products for $\ensuremath{\rho}(1450)\ensuremath{\rightarrow}\ensuremath{\omega}{\ensuremath{\pi}}^{0}$ and $\ensuremath{\rho}(1450)\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ decays. The obtained cross section data have been also used to test the conservation of vector current hypothesis.

We analyze a $37\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ data sample collected with the SND detector at the VEPP-2000 ${e}^{+}{e}^{\ensuremath{-}}$ collider in the center-of-mass energy range 1.05--2.00 GeV and present an updated measurement of the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\omega}{\ensuremath{\pi}}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}$ 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 $\ensuremath{\rho}$-like states and used to test the conserved vector current hypothesis in the ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\omega}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\nu}}_{\ensuremath{\tau}}$ decay.

Abstract The process $$e^+e^-\rightarrow n{\bar{n}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:mi>n</mml:mi> <mml:mover> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> </mml:math> is studied in the experiment at the VEPP-2000 $$e^+e^-$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> </mml:mrow> </mml:math> collider with the SND detector. The technique of the time measurements in the multichannel NaI(Tl) electromagnetic calorimeter is used to select $$n{\bar{n}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>n</mml:mi> <mml:mover> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> </mml:math> events. The value of the measured cross section in the center-of-mass energy range from 1.894 to 2 GeV varies from 0.5 to 0.35 nb. The effective neutron timelike form factor is derived from the measured cross section and compared with the proton form factor. The ratio of the neutron electric and magnetic form factors is obtained from the analysis of the antineutron polar angle distribution and found to be consistent with unity.

The $e^+e^-\to K^+K^-$ cross section is measured in the center-of-mass energy range $1.05-2.00$ GeV at the SND detector. The measurement is based on data with an integrated luminosity of 35 pb$^{-1}$ collected at the VEPP-2000 $e^+e^-$-collider. The obtained results are consistent with the previous most accurate data obtained in the BABAR experiment and have a comparable accuracy.

A bstract The cross section of the process e + e − → π + π − has been measured in the Spherical Neutral Detector (SND) experiment at the VEPP-2000 e + e − collider VEPP-2000 in the energy region 525 &lt; $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> &lt; 883 MeV. The measurement is based on data with an integrated luminosity of about 4.6 pb − 1 . The systematic uncertainty of the cross section determination is 0.8% at $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> &gt; 0 . 600 GeV. The ρ meson parameters are obtained as m ρ = 775 . 3 ± 0 . 5 ± 0 . 6 MeV, Γ ρ = 145 . 6 ± 0 . 6 ± 0 . 8 MeV, B ρ → e + e− × B ρ → π + π− = (4 . 89 ± 0 . 02 ± 0 . 04) × 10 − 5 , and the parameters of the e + e − → ω → π + π − process, suppressed by G -parity, as B ω → e + e− × B ω → π + π− = (1 . 32 ± 0 . 06 ± 0 . 02) × 10 − 6 and and ϕ ρω = 110 . 7 ± 1 . 5 ± 1 . 0 degrees.

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 e+e−→ηγ cross section has been measured in the center-of-mass energy range 1.07–2.00 GeV using the decay mode η→3π0, π0→γγ. The analysis is based on 36 pb−1 of integrated luminosity collected with the SND detector at the VEPP-2000 e+e− collider. The measured cross section of about 40 pb at 1.5 GeV is explained by decays of the ρ(1450) and ϕ(1680) resonances.Received 29 December 2013DOI:https://doi.org/10.1103/PhysRevD.90.032002© 2014 American Physical Society

The ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\eta}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ cross section is measured at the Spherical Neutral Detector (SND) detector in the $\ensuremath{\eta}$ decay mode $\ensuremath{\eta}\ensuremath{\rightarrow}3{\ensuremath{\pi}}^{0}$. The analysis is based on the data sample with an integrated luminosity of $32.7\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ collected at the VEPP-2000 ${e}^{+}{e}^{\ensuremath{-}}$ collider in the center-of-mass energy range $\sqrt{s}=1.075--2.000\text{ }\text{ }\mathrm{GeV}$. The data obtained in the $\ensuremath{\eta}\ensuremath{\rightarrow}3{\ensuremath{\pi}}^{0}$ decay mode are found to be in agreement with the previous SND measurements in the $\ensuremath{\eta}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$ mode. Therefore the measurements in the two modes are combined.

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.

The process $e^+e^-\to\omega\eta\pi^0$ is studied in the energy range $1.45-2.00$ GeV using data with an integrated luminosity of 33 pb$^{-1}$ accumulated by the SND detector at the $e^+e^-$ collider VEPP-2000. The $e^+e^-\to\omega\eta\pi^0$ cross section is measured for the first time. The cross section has a threshold near 1.75 GeV. Its value is about 2 nb in the energy range $1.8-2.0$ GeV. The dominant intermediate state for the process $e^+e^- \to \omega\eta\pi^0$ is found to be $\omega a_0(980)$.

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.

Abstract The process $$e^+e^-\rightarrow \eta \eta \gamma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:mi>η</mml:mi> <mml:mi>η</mml:mi> <mml:mi>γ</mml:mi> </mml:mrow> </mml:math> is studied in the center-of-mass energy range 1.17–2.00 GeV using data with an integrated luminosity of 201 pb $$^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow /> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> collected by the SND detector at the VEPP-2000 $$e^+e^-$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> </mml:mrow> </mml:math> collider. The $$e^+e^-\rightarrow \eta \eta \gamma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:mi>η</mml:mi> <mml:mi>η</mml:mi> <mml:mi>γ</mml:mi> </mml:mrow> </mml:math> cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the $$\phi \eta $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>ϕ</mml:mi> <mml:mi>η</mml:mi> </mml:mrow> </mml:math> intermediate state. Our result on the $$e^+e^-\rightarrow \eta \eta \gamma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:mi>η</mml:mi> <mml:mi>η</mml:mi> <mml:mi>γ</mml:mi> </mml:mrow> </mml:math> cross section is consistent with the $$e^+e^-\rightarrow \phi \eta $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:mi>ϕ</mml:mi> <mml:mi>η</mml:mi> </mml:mrow> </mml:math> measurement in the $$\phi \rightarrow K^+ K^-$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>ϕ</mml:mi> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>-</mml:mo> </mml:msup> </mml:mrow> </mml:math> mode. The search for radiative processes contributing to the $$e^+e^-\rightarrow \eta \eta \gamma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:mi>η</mml:mi> <mml:mi>η</mml:mi> <mml:mi>γ</mml:mi> </mml:mrow> </mml:math> cross section is performed, and no significant signal is observed.

The process $e^+e^- \to \pi^+\pi^-\pi^0\eta$ is studied in the center-of-mass energy region below 2 GeV with the SND detector at the VEPP-2000 $e^+e^-$ collider. The four intermediate states contribute to this process: $\omega\eta$, $\phi\eta$, $a_0(980)\rho$, and a structureless $\pi^+\pi^-\pi^0\eta$ state. We measure the total $e^+e^- \to \pi^+\pi^-\pi^0\eta$ cross section and the cross sections for its components: $\omega\eta$, $\phi\eta$, and a sum of $a_0(980)\rho$ and the structureless state. Our results are in agreement with previous measurements and have comparable or better accuracies.

The process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}$ is studied with the SND detector at the VEPP-2000 ${e}^{+}{e}^{\ensuremath{-}}$ collider. Basing on data with an integrated luminosity of $41\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ recorded in 2010-2012 we measure the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}$ 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 ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}$ is studied for the first time.

Spherical Neutral Detector (SND) is a general purpose non-magnetic detector for experiments at VEPP-2000 e+e− collider in Novosibirsk in the energy range 2E=0.4–2.0GeV. Charged particle track coordinates are measured using drift and proportional chambers placed in a common gas volume. Particle identification is performed using energy deposition in the drift chamber at low particle momenta p⩽300MeV and aerogel threshold counters at high particle momenta p⩾300MeV. Photon energies are measured using 3-layer spherical electromagnetic calorimeter. Muons penetrating the detector and cosmic background muons are detected by the muon system based on proportional tubes and plastic scintillator counters. At present the detector is operating at VEPP-2000.

The Monte Carlo event generator GGRESRC is described. The generator is developed for the simulation of events of the two-photon process e+e−→e+e−R, where R is a pseudoscalar resonance, π0, η, η′, ηc, or ηb. The program is optimized for the generation of two-photon events in the single-tag mode. For single-tag events, radiative correction simulation is implemented in the generator including photon emission from the initial and final states. Program title: GGRESRC Catalogue identifier: AEQB_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEQB_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 6059 No. of bytes in distributed program, including test data, etc.: 61284 Distribution format: tar.gz Programming language: FORTRAN 77. Computer: PC, main frame. Operating system: Linux, Unix. RAM: 512 kb Classification: 11.2, 11.6. External routines: CERN program library (Necessary routines are included in the distribution.) Nature of problem: Simulation of the e+e− experiment on measurement of the pseudoscalar meson–photon transition form factors in the single tag mode Solution method: Events, that are four-momenta of particles, produced in e+e− collision according to the theoretical cross section, are generated by Monte Carlo method. Additional comments: The theoretical uncertainty of the formulas used is estimated to be about 1% [1] Running time: On Intel Pentium CPU @ 3.4 GHz simulation of 106 events e+e−→e+e−π0 with cuts (test run) takes 110 s. References: [1] S. Ong, P. Kessler, Phys. Rev. D 38 (1988) 2280.

A search for direct production of the f1(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−→f1(1285) candidate events are found at the peak of the resonance and zero events beyond the resonance. The significance of the e+e−→f1(1285) signal is 2.5σ. The cross section at the maximum of the resonance is found to be σ(e+e−→f1)=45−24+33 pb. The corresponding branching fraction B(f1(1285)→e+e−)=(5.1−2.7+3.7)×10−9. We consider this result as a first indication of the process e+e−→f1(1285). The measured branching fraction is consistent with the theoretical prediction.

New results on exclusive hadron production in e+e− annihilation obtained in experiments with the SND detector at the VEPP-2M and VEPP-2000 e+e− colliders are presented.

Abstract The process $$e^+e^-\rightarrow \eta \pi ^0\gamma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:mi>η</mml:mi> <mml:msup> <mml:mi>π</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mi>γ</mml:mi> </mml:mrow> </mml:math> is studied in the center-of-mass energy range 1.05–2.00 GeV using data with an integrated luminosity of 94.5 $$\hbox {pb}^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mtext>pb</mml:mtext> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> collected by the SND detector at the VEPP-2000 $$e^{+}e^{-}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> </mml:mrow> </mml:math> collider. The $$e^+e^-\rightarrow \eta \pi ^0\gamma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:mi>η</mml:mi> <mml:msup> <mml:mi>π</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mi>γ</mml:mi> </mml:mrow> </mml:math> cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the $$\omega \eta $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>ω</mml:mi> <mml:mi>η</mml:mi> </mml:mrow> </mml:math> intermediate state. The measured cross section of the subprocess $$e^+e^-\rightarrow \omega \eta \rightarrow \eta \pi ^0\gamma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:mi>ω</mml:mi> <mml:mi>η</mml:mi> <mml:mo>→</mml:mo> <mml:mi>η</mml:mi> <mml:msup> <mml:mi>π</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mi>γ</mml:mi> </mml:mrow> </mml:math> is consistent with previous measurements in the $$e^+e^-\rightarrow \pi ^+\pi ^-\pi ^0\eta $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:msup> <mml:mi>π</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mi>η</mml:mi> </mml:mrow> </mml:math> mode. It is found, with a significance of $$5.6\sigma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>5.6</mml:mn> <mml:mi>σ</mml:mi> </mml:mrow> </mml:math> , that the process $$e^+e^-\rightarrow \eta \pi ^0\gamma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:mi>η</mml:mi> <mml:msup> <mml:mi>π</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mi>γ</mml:mi> </mml:mrow> </mml:math> 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. $$e^+e^-\rightarrow a_{0}(1450)\gamma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:msub> <mml:mi>a</mml:mi> <mml:mn>0</mml:mn> </mml:msub> <mml:mrow> <mml:mo>(</mml:mo> <mml:mn>1450</mml:mn> <mml:mo>)</mml:mo> </mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> </mml:math> , is measured. It is found to be 15–20 pb in the wide energy range from 1.3 to 1.9 GeV.

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 $\omega(1420)\to\pi^+\pi^-\pi^0$.

Abstract Preliminary results of the first experiments at the new VEPP-2000 e + e − collider are presented. The experiments have been carried out in the center of mass energy range 1–2 GeV with instant luminosity 10 30 – 10 31 cm − 2 s − 1 and total integrated luminosity of about 10 pb − 1 . The main e + e − annihilation cross sections, π + π − π 0 π 0 , π + π − π 0 , π 0 π 0 γ , a n d π + π − η , have been measured. The cross section of nucleon–antinucleon production is also presented.

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.

Two experiments, CMD-3 and SND, collected over 100 pb−1 in total taking data in 2011-2013 at the VEPP-2000 electron-positron collider. The data sample covers the whole available c.m. energy range from 0.32 GeV to 2.0 GeV. An upgrade of VEPP-2000 started in the second half of 2013, aimed at the luminosity increase up to 10 times at 2.0 GeV. Data taking is expected to resumed in 2015. The current results of analysis of the collected data for various modes of e+ e− → hadrons are discussed.

The preliminary results on multihadron processes obtained with the SND detector at the e + e − collider VEPP-2000 in the energy range from 1 to 2 GeV are presented. The results are interesting in connection with their contribution to the total hadronic cross section, the muon g-2 and a possibility to study excited vector mesons properties. The nucleon anti-nucleon production was also studied.

It’s good known the difference in 3.5 sigma between the muon (g – 2) experimental result and its calculation in Standard Model. To clarify this intriguing discrepancy the new stage of muon (g – 2) measurement is under preparation at Fermi National Laboratory. On other hand, regular data taking for measurements of hadron cross section production in e+ e− annihilations is under way since December 2010 at the electron-positron collider VEPP-2000 with the CMD-3 and SND detectors. The collected data sample corresponds to about 60 inverse picobarns of integrated luminosity per detector in the energy range from 0.32 up to 2 GeV. Preliminary analysis of various hadronic cross sections has been performed.

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.

Recent results from the SND detector obtained in experiments at the VEPP-2000 e+e- collider are presented. The reactions e+e− → ηπ+π−, e+e− → K+K−, e+e− → π+π−π0, e+e− → ωπ0, e+e− → ωη have been studied in the energy region 1.05–2.00 GeV. The neutron and proton electromagnetic form factors have been measured in the energy range from the threshold up to 2 GeV. The result of the search of the rare process e+e− → η′ is also presented.

Recent results on various cross sections of e+e−→hadrons obtained with the SND and CMD3 detectors at the VEPP-2000 collider in the energy range up to 2 GeV are presented. The final states studied include e+e−→π+π−, K+K−, π+π−π0, π+π−π0π0, ηπ+π−, ωη, ηγ and others. The measured cross sections are important since they contribute to the total hadronic cross section, muon g-2 and parameters of excited vector mesons. The nucleon-antinucleon production at threshold was also studied.

The SND is a non-magnetic detector at the VEPP-2000 e+e− collider (BINP, Novosibirsk) designed for hadronic cross-section measurements in the center-of-mass energy range up to 2 GeV. The important part of the detector is a segmented electromagnetic calorimeter (EMC) with three layers of NaI(Tl) counters. The EMC signal shaping and digitizing electronics based on FADC allow one to obtain both the signal amplitude and the arrival time. We describe the EMC signal processing and how the EMC measured time is applied in event reconstruction and physics analysis.

The process e+e−→ωπ0→π+π−π0π0 is studied in the center-of-mass energy region 1.05–2.00 GeV using data with an integral luminosity of about 35 pb−1 collected with the SND detector at the VEPP-2000 e+e− collider. In the energy range under study, the value of the measured Born cross section varies from 0.7 to 18 nb. The statistical uncertainty of the cross section is 2%–23%, while the systematic uncertainty is in the range of 3.0%–14.2%. The results are consistent with previous measurements but have better accuracy.4 MoreReceived 6 September 2023Accepted 1 November 2023DOI:https://doi.org/10.1103/PhysRevD.108.092012Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasHadron productionLepton-lepton interactionsPhysical SystemsLight mesonsPropertiesForm factorsParticles & Fields

We review here recent results on [Formula: see text] annihilation to hadrons below 2 GeV obtained with the SND detector at the VEPP-2000 collider. Among others we report cross sections and dynamics properties for the [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text].

Results are presented from measuring the e+e− → n¯n cross section and effective neutron timelike form factor. Data are collected in 2020–2021 at the VEPP-2000 e+e− collider in the 1891 to 2007 MeV center-of-mass range of energies. The general purpose nonmagnetic SND detector is used to detect neutron–antineutron events. The time-of-flight approach is used to select n¯n events. The measuredcross section is 0.4–0.6 nbn. The neutron form factor in the investigated range of energies varies from 0.3 to 0.2.

Results of the first measurements of the cross sections for the e+e−→pp¯ and e+e−→nn¯ with the SND detector are presented. The analysis is based on data with integrated luminosity of 2.8pb−1, collected in 2011 by the SND detector at the VEPP-2000 e+e− collider in the energy range above nucleon production threshold.

Preliminary results of the SND experiment at the VEPP-2000 e+e− collider are presented. Data corresponding to about 40 pb−1 of integrated luminosity were collected in the e+e− c.m. energy range from 1.05 to 2.00 GeV. The cross sections for e+e− → ωπ0, π+π−4π0, , have been measured.

Abstract The process $$e^+e^-\rightarrow K^+K^-\pi ^0$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:msup> <mml:mi>π</mml:mi> <mml:mn>0</mml:mn> </mml:msup> </mml:mrow> </mml:math> is studied with the SND detector at the VEPP-2000 $$e^+e^-$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> </mml:mrow> </mml:math> collider. Basing on data with an integrated luminosity of 26.4 $$\hbox {pb}^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mtext>pb</mml:mtext> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> we measure the $$e^+e^-\rightarrow K^+K^-\pi ^0$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:msup> <mml:mi>π</mml:mi> <mml:mn>0</mml:mn> </mml:msup> </mml:mrow> </mml:math> cross section in the center-of-mass energy range from 1.28 up to 2 GeV. The measured mass spectrum of the $$K\pi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>K</mml:mi> <mml:mi>π</mml:mi> </mml:mrow> </mml:math> system indicates that the dominant mechanism of this reaction is the transition through the $$K^{*}(892)K$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>K</mml:mi> <mml:mrow> <mml:mrow /> <mml:mo>∗</mml:mo> </mml:mrow> </mml:msup> <mml:mrow> <mml:mo>(</mml:mo> <mml:mn>892</mml:mn> <mml:mo>)</mml:mo> </mml:mrow> <mml:mi>K</mml:mi> </mml:mrow> </mml:math> intermediate state. The cross section for the $$\phi \pi ^0$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>ϕ</mml:mi> <mml:msup> <mml:mi>π</mml:mi> <mml:mn>0</mml:mn> </mml:msup> </mml:mrow> </mml:math> intermediate state is measured separately. The SND results are consistent with previous measurements in the BABAR experiment and have comparable accuracy. We study the effect of the interference between the $$\phi \pi ^0$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>ϕ</mml:mi> <mml:msup> <mml:mi>π</mml:mi> <mml:mn>0</mml:mn> </mml:msup> </mml:mrow> </mml:math> and $$K^*K$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>∗</mml:mo> </mml:msup> <mml:mi>K</mml:mi> </mml:mrow> </mml:math> amplitudes. It is found that the interference gives sizable contribution to the measured $$e^+e^- \rightarrow \phi \pi ^0\rightarrow K^+K^-\pi ^0$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:mi>ϕ</mml:mi> <mml:msup> <mml:mi>π</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:msup> <mml:mi>π</mml:mi> <mml:mn>0</mml:mn> </mml:msup> </mml:mrow> </mml:math> cross section below 1.7 GeV.

A bstract The cross section of the process e + e − → π + π − has been measured in the Spherical Neutral Detector (SND) experiment at the VEPP-2000 e + e − collider VEPP-2000 in the energy region 525 &lt; $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> &lt; 883 MeV. The measurement is based on data with an integrated luminosity of about 4.6 pb − 1 . The systematic uncertainty of the cross section determination is 0.8% at $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> &gt; 0 . 600 GeV. The ρ meson parameters are obtained as m ρ = 775 . 3 ± 0 . 5 ± 0 . 6 MeV, Γ ρ = 145 . 6 ± 0 . 6 ± 0 . 8 MeV, B ρ → e + e− × B ρ → π + π− = (4 . 89 ± 0 . 02 ± 0 . 04) × 10 − 5 , and the parameters of the e + e − → ω → π + π − process, suppressed by G -parity, as B ω → e + e− × B ω → π + π− = (1 . 32 ± 0 . 06 ± 0 . 02) × 10 − 6 and and ϕ ρω = 110 . 7 ± 1 . 5 ± 1 . 0 degrees.

The SND is a non-magnetic detector deployed at the VEPP-2000 e + e − collider (BINP, Novosibirsk) for hadronic cross-section measurements in the center of mass energy range below 2 GeV. The important part of the detector is a hodoscopic electromagnetic calorimeter (EMC) with three layers of NaI(Tl) counters. EMC signal shaping and digitizing electronics based on FADC allow us to obtain both the energy deposition and the signal arrival time. We demonstrate how EMC time is applied to detect background pileup and cosmic events.

Recent results on e+e− annihilation to hadrons from SND experiment at VEPP-2000 and VEPP-2M colliders are presented. Corresponding data set is about 100 pb−1 of integrated luminosity collected at the energy region s below 2 GeV. The processes e+e−→K+K−, π0γ, ηπ+π−π0 and ωπ0η have been studied.

At the end of 2016 the SND detector resumed data taking at the upgraded VEPP-2000 e + e − collider. The analysis of data accumulated in 2010-2013 with an integrated lumonosity of 70 pb −1 is continuing. Recent results on measurements of various hadronic cross sections are presented.

Recent results on study of exclusive processes of e + e -annihilation into hadrons below 2 GeV obtained at the SND detector are presented.The analysis are based on data collected at the VEPP-2M and VEPP-2000 colliders.In particular, we present the measurements of the e + e -→ ηπ + π -, e + e -→ ηK + K -, e + e -→ K S K L π 0 cross sections, the preliminary results on study of the e + e -→ π + π -, e + e -→ n n and e + e -→ π 0 γ, and the upper limit for η → e + e -decay branching fraction

A bstract A factorization hypothesis is tested by examining a form factor of the ωπ production in hadronic B 0 → D ∗± ωπ ∓ decays. The form factor is compared to that from available τ -lepton as well as e + e − data using the conserved vector current hypothesis. The difference of normalizations of form factor shapes from B and τ ( e + e − ) data indicates the important role of the large N c limit in QCD. Moreover, the growth of the difference between the form factors with the ωπ invariant mass is related to the perturbative QCD corrections of factorization. The current precision of B data does not allow one to find any evidence of corrections to factorization. A promising study could be performed with the Belle II and LHCb data sets.

During years 2011 and 2012 data taking runs have been carried out at VEPP-2000 e + e - collider to measure the production of the nucleon-antinucleon pairs [Formula: see text] near threshold. In this talk the preliminary results on the nucleon timelike electromagnetic form factors (FF) and the |G E /G M | ratio are presented.

The experiments have been carried out with the SND detector at the VEPP-2000 e+e− collider in the energy range from 0.3 to 2.0 GeV. The cross sections for the processes e+e− → ωπ0, K+K−, 3π, ηπ+π−, ηγ, pp̄, nn̄ have been measured.

The cross sections , , , , K+K−, , , have been measured with the spherical neutral detector at the VEPP-2000 e+e− collider in the energy range from 0.3 to 2.0 GeV.

A search for the rare decay $\eta^{\prime} \to e^+e^-$ has been performed with the SND detector at the VEPP-2000 $e^+e^-$ collider. The inverse reaction $e^+e^- \to \eta^{\prime}$ and $\eta^{\prime}$ five decay chains have been used for this search. The upper limit $\Gamma_{\eta^{\prime} \to e^+e^-}<0.002$ eV at the 90\% confidence level has been set. A sensitivity of SND in a search for $\eta \to e^+e^-$ decay has been studied. For this perpose we have analyzed a data sample with an integrated luminosity of 108 nb$^{-1}$ collected in the center-of-mass energy range 520-580 MeV. There are no background events for the reaction $e^+e^- \to \eta$ with decay $\eta \to \pi^0\pi^0\pi^0$ have been found. In the absence of background, a sensitivity to $B(\eta \to e^+e^-)$ of 10$^{-6}$ can be reached during two weeks of VEPP-2000 operation.

The cross section for the process e + e -→ ωπ 0 → π 0 π 0 γ has been measured in the center-of-mass energy range 1.05-2.00GeV.The experiment has been performed at the e + e -collider VEPP-2000 with the SND detector.The measured e + e -→ ωπ 0 cross section above 1.4 GeV is the most accurate to date.Below 1.4 GeV our data are in good agreement with the previous SND and CMD-2 measurements.Data on the e + e -→ ωπ 0 cross section are well described by the Vector Meson Dominance (VMD) model with two excited ρ-like states.From the measured cross section we have extracted the γ * → ωπ 0 transition form factor.It has been found that the VMD model cannot describe simultaneously our data and data obtained from the ω → π 0 µ + µ - decay.We have also tested Conserved Vector Current (CVC) hypothesis comparing our results on the e + e -→ ωπ 0 cross section with data on the τ -→ ωπ -ν τ decay and have found that the CVC hypothesis works well within reached experimental accuracy of about 5%.

A search for the rare decay $η^{\prime} \to e^+e^-$ has been performed with the SND detector at the VEPP-2000 $e^+e^-$ collider. The inverse reaction $e^+e^- \to η^{\prime}$ and $η^{\prime}$ five decay chains have been used for this search. The upper limit $Γ_{η^{\prime} \to e^+e^-}&lt;0.002$ eV at the 90\% confidence level has been set. A sensitivity of SND in a search for $η\to e^+e^-$ decay has been studied. For this perpose we have analyzed a data sample with an integrated luminosity of 108 nb$^{-1}$ collected in the center-of-mass energy range 520-580 MeV. There are no background events for the reaction $e^+e^- \to η$ with decay $η\to π^0π^0π^0$ have been found. In the absence of background, a sensitivity to $B(η\to e^+e^-)$ of 10$^{-6}$ can be reached during two weeks of VEPP-2000 operation.

Preliminary results on e+e−→3π,4π,ωπ0,ηπ+π−,pp¯,nn¯ cross sections obtained with SND detector at VEPP-2000 collider are reported. The data were collected in 2010–2011 in the energy range 2E=1.0–2.0 GeV.

В работе измерено сечение процесса е+е- → ωπ0 → π0 π0 γ в интервале энергии от 1.1 до 1.9 ГэВ. Измерение проведено в эксперименте со Сферическим нейтральным детектором на е+е_-коллайдере ВЭПП-2000. В интервале энергии 1.1-1.4 ГэВ полученные данные хорошо согласуются с предыдущими измерениями СНД и К M Л-2. Измерено сечение выше 1.4 ГэВ.

In an experiment with the Spherical Neutral Detector at VEPP-2M collider the cross section of the process e+e− → π+π−π0π0 was measured. At energies √s < 920 MeV this cross section was measured for the first time. The energy dependence of the cross section is well discribed by the vector dominance model with contributions from ρ, ρ', ρ'' mesons. The decay probability ρ → π +π−π0π0 was found to be Bρ = (1.60±0.74±0.18) × 10−5. The upper limit for the decay ω → π+π−π0π0 was improved by two orders of magnitude compared to the previous measurements and is Bω < 2 × 10−4 at 90% confidence level.

Recent results of the SND detector experiments are presented. Data were taken at the VEPP-2000 and the VEPP-2M e+e− colliders in the Novosibirsk in the c.m. energy ranges from 0.3 to 2.00 GeV. Integrated luminosity used are 70pb-1 and 25pb-1 respectively. The cross sections of the e+e− → π0γ, K+K−, ωπ0, π+π−π0η, ωη, ωηπ0 processes has been measured.

Recent results of the SND experiment at the VEPP-2000 collider on e +e − annihilation to hadrons below 2 GeV are presented. In particular, we discuss measurements of the e +e − → π +π − and e +e − → nn¯ cross sections. The processes e +e − → π +π −π 0 , K+K−π 0 , ηπ0 γ and 2ηγ were under investigation as well. The preliminary results on the e +e − → ωπ0 → π +π −2π 0 cross section measurement are also presented.

We present recent results on study of exclusive processes of e + e -annihilation into hadrons with the SND detector.Data were collected at the VEPP-2000 e + e -collider in the center-of-mass energy range from 0.3 to 2 GeV.In particular, we have measured the cross sections for e + e -→ π + π -and n n, studied the radiative decays of excited light vector mesons to π 0 γ and ηπ 0 γ, and performed a search for the rare processes of e + e -annihilation into C-even resonances η and f 1 (1285).

Recent results on study of exclusive processes of e + e -annihilation into hadrons below 2 GeV obtained at the SND detector are presented.The analyses are based on data collected at the VEPP-2M and VEPP-2000 colliders.In particular, we present the precise measurements of the e + e -→ π 0 γ and e + e -→ K + K -cross sections, and the first measurements of the e + e -→ ωπ 0 η and e + e -→ π + π -π 0 η reactions.

Latest results on study of processes of e + e annihilation into exclusive hadronic states at √ s < 2GeV obtained in the SND experiment at the VEPP-2M and VEPP-2000 colliders are presented.In particular, we announce results of the precise measurements of the e + e → π 0 γ and e + e → K + K - cross sections, the first measurements of the e + e → ωπ 0 η and e + e → π + π -π 0 η reactions and preliminary results of measurement of the e + e → π + π -cross section in energy range 0.5 < √ s < 0.9 GeV.

Presented are recent results of experiments on the SND detector. Data were collected on the VEPP-2000 and VEPP-2M $${{e}^{ + }}{{e}^{ - }}$$ colliders (Novosibirsk) in the c.m. energy region 0.3–2.0 GeV. Integrated luminusity used is 70 and 25 pb–1 respectively. Cross section of the $${{e}^{ + }}{{e}^{ - }} \to {{\pi }^{0}}\gamma ,$$ $${{e}^{ + }}{{e}^{ - }} \to {{\pi }^{ + }}{{\pi }^{ - }}{{\pi }^{0}}\eta ,$$ $${{e}^{ + }}{{e}^{ - }} \to \omega \eta {{\pi }^{0}}$$ processes is measured.

Since December 2010 the CMD-3 and SND detectors detectors collect data at the VEPP-2000 electron-positron collider. In 2013-2015 the injection facility of the collider has undergone an upgrade of the injection system. The new BINP injection complex has been connected to the VEPP-2000 collider, so the restrictions connected to the lack of positrons and limited beam energy transfer do not apply any more. The collider luminosity in whole energy range is restricted now only by beam-beam effects. VEPP-2000 collider started to collect data with two detectors at 2016 year. The collected data sample since 2010 corresponds more than 100 pb -1 of integrated luminosity per detector in the c.m. energy between 0.32 and 2GeV. We will report here results of analysis of various hadronic cross sections from detectors both published and preliminary. These measurements are important by themselves and also because of the implications for anomaly of the magnetic moment of a muon (g-2) discrepancy.

The Spherical Neutral Detector (SND) is an experiment for e+e− annihilation study at low energies 0.2−2 GeV. The light quark anti−quark bound states are the main subject of study at these energies. They express themselves as resonances in the e+e− hadronic cross sections. Hadronic cross sections could be recalculated to hadronic vacuum polarization (HVP). The Standard Model predictions today are limited by HVP which is not calculable with modern QCD theory. In this talk we present the review of the hadronic cross sections measurements at SND and new measurements: e+e− → π+π−, π0γ, π+π−π0, ωπ0, K+K−η, η, KsKLπ0, π+π−π0η, ωπ0η e.t.c.

We present current status of the SND and CMD-3 experiments at the VEPP-2000 e + e − collider and recent result of data analysis on the processes $e^+e^-\rightarrow\pi^+\pi^-,n\overline n,\pi^+\pi^-\eta,\pi^+\pi^-\pi^0\eta,K_SK_L\pi^0$, etc.

In 2017 the detector SND resumed data taking at the VEPP-2000 e+e− collider after its upgrade. Using of a new positron source allows significantly increase collider luminosity. We report the current status of the experiment and recent result of data analysis, in particular, on the processes e+e−→π+π−, nn‾, K+K−η, π+π−η, KSKLπ0, π+π−π0η, π0γ, ωπ0, and η→e+e−.

Precise study of the hadrons production in \bm{e^+e^-} <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mstyle mathvariant="bold"><mml:msup><mml:mi>𝐞</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>𝐞</mml:mi><mml:mo>−</mml:mo></mml:msup></mml:mstyle></mml:math> annihilation at low energies provides important information about interactions of light quarks and spectroscopy of their bound states. These studies are especially important for theoretical calculations of the muon \bm{(g-2)} <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mstyle mathvariant="bold"><mml:mo stretchy="false" form="prefix">(</mml:mo><mml:mi>𝐠</mml:mi><mml:mo>−</mml:mo><mml:mn>2</mml:mn><mml:mo stretchy="false" form="postfix">)</mml:mo></mml:mstyle></mml:math> via the Standard Model because of the present difference between theoretical and experimental values exceeds three standard deviations. In this report we will discuss current status and recent results obtained by the CMD-3 experiment and will give a brief look to status of the BaBar and Belle II experiments.

A factorization hypothesis is tested by examining a form factor of the $\omega \pi$ production in hadronic $B^0 \to D^{*\pm} \omega \pi^\mp$ decays. The test relies on existing $B$, $\tau$ and $e^+e^-$ data.

We present recent experimental results for e+e annihilation into hadrons below 2 GeV obtained with the SND detector at the VEPP-2000 collider.The analyses are based on data collected in the detector runs from 2010 to 2017.During the period from 2014 to 2016 collider and detector underwent significant upgrades which allowed an increase in luminosity and detector efficiency.In particular, results of studying e + e -→ π + π -, η → e + e -, e + e -→ n n, e + e -→ K + K -η, e + e -→ π + π -η, e + e -→ K S K L π 0 , e + e -→ π + π -π 0 η, e + e -→ ωπ 0 , e + e -→ π 0 γ, and e + e -→ π + π -4π 0 reactions are considered in this paper.

Recent SND results on the study of the process e + e − → π 0 γ are presented. The study is based on data collected with the SND detector on the VEPP-2M and VEPP-2000 e + e − colliders with an integrated luminosity of 25 and 46 pb −1 , respectively. The VEPP-2M data used in this analysis are recorded in the center-of-mass energy range 0.60-1.38 GeV, while the VEPP-2000 data in the range 1.05-2.00 GeV.

SND detector operates at the VEPP-2000 collider (BINP, Novosibirsk). To improve events selection for physical analysis and facilitate online detector control we developed new data quality monitoring (DQM) system. The system includes online and reprocess control modules, automatic decision making scripts, interactive (web based) and program (python) access to various quality estimates. This access is implemented with node.js server with data in RDBMS MySQL. We describe here general system logics, its components and some implementation details.

Abstract The SND detector has been operating at the VEPP-2000 collider (BINP, Russia) for several years. We present its new DQM system. The system deals with multiple parameters being numbers, histograms or user opinions to form a data quality decision (good, bad, etc). It calculates SND subsystem and overall statuses and produces summaries available via web-interface. The system supports multiple parameter sets for different usages like daily checks, precise subsystem control, preparing data for processing, etc. The parameter values are analyzed using special ROOT macros yielding quality checks that could be supplemented or corrected by users. The system is a part of a new SND information system implemented as a web application using Node.js and MySQL. The ROOT macros are written by SND subsystems experts using a simple framework. Histograms are displayed using JSROOT. The system is put into production. It is consistent, however there are some improvements to implement.

SND detector operates at the VEPP-2000 collider (BINP, Novosibirsk). To improve events selection for physical analysis and facilitate online detector control we developed new data quality monitoring (DQM) system. The system includes online and reprocess control modules, automatic decision making scripts, interactive (web based) and program (python) access to various quality estimates. This access is implemented with node.js server with data in RDBMS MySQL. We describe here general system logics, its components and some implementation details.

Recent results on e + e -annihilation to hadrons obtained in the SND experiment at the VEPP-2000 collider are presented.The data collected in 2010-2018 in the energy region below 2 GeV are analyzed.The processes e + e -→ π + π -, n n, ηπ 0 γ, π + π -π 0 are studied.Search for e + e - annihilation to C-even resonance f 1 (1285) is performed.

The process $e^+e^-\toηηγ$ 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 $e^+e^-\toηηγ$ cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the $ϕη$ intermediate state. Our result on the $e^+e^-\toηηγ$ cross section is consistent with the $e^+e^-\toϕη$ measurement in the $ϕ\to K^+ K^-$ mode. The search for radiative processes contributing to the $e^+e^-\toηηγ$ cross section is performed, and no significant signal is observed.