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Publisher Copyright: © 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society. The bright blazar OJ 287 routinely parades high brightness bremsstrahlung flares, which are explained as being a result of a secondary supermassive black hole (SMBH) impacting the accretion disc of a more massive primary SMBH in a binary system. The accretion disc is not rigid but rather bends in a calculable way due to the tidal influence of the secondary. Next, we refer to this phenomenon as a variable disc level. We begin by showing that these flares occur at times predicted by a simple analytical formula, based on general relativity inspired modified Kepler equation, which explains impact flares since 1888. The 2022 impact flare, namely flare number 26, is rather peculiar as it breaks the typical pattern of two impact flares per 12-yr cycle. This is the third bremsstrahlung flare of the current cycle that follows the already observed 2015 and 2019 impact flares from OJ 287. It turns out that the arrival epoch of flare number 26 is sensitive to the level of primary SMBH's accretion disc relative to its mean level in our model. We incorporate these tidally induced changes in the level of the accretion disc to infer that the thermal flare should have occurred during 2022 July-August, when it was not possible to observe it from the Earth. Thereafter, we explore possible observational evidence for certain pre-flare activity by employing spectral and polarimetric data from our campaigns in 2004/05 and 2021/22. We point out theoretical and observational implications of two observed mini-flares during 2022 January-February.

Aims. The fact that the O-type close binary star system AO Cassiopeiae exhibits variable phase-locked linear polarization has been known since the mid-1970s. In this work, we re-observe the polarization arising from this system more than 50 yr later to better estimate the interstellar polarization and to independently derive the orbital parameters, such as inclination, i, orientation, Ω, and the direction of the rotation for the inner orbit from the phase-folded polarization curves of the Stokes q and u parameters. Methods. The Dipol-2 polarimeter was used to obtain linear polarization measurements of AO Cassiopeiae in the B, V, and R passbands with the T60 remotely controlled telescope at an unprecedented accuracy level of ~0.003%. We have obtained the first proper quantification of the interstellar polarization in the direction heading towards AO Cas by observing the polarization of three neighboring field stars. We employed a Lomb-Scargle algorithm and detected a clear periodic signal for the orbital period of AO Cas. The standard analytical method based on a two-harmonics Fourier fit was used to obtain the inclination and orientation of the binary orbit. Results. Our polarimetric data exhibited an unambiguous periodic signal at 1.76 days, thus confirming the orbital period of the binary system of 3.52 days. Most of the observed polarization is of interstellar origin. The de-biased values of the orbital inclination are i = 63° + 2°/−3° and orientation of Ω = 29º(209º) ± 8°. The direction of the binary system rotation on the plane of the sky is clockwise.

Full list of authors: Middei, Riccardo; Liodakis, Ioannis; Perri, Matteo; Puccetti, Simonetta; Cavazzuti, Elisabetta; Di Gesu, Laura; Ehlert, Steven R.; Madejski, Grzegorz; Marscher, Alan P.; Marshall, Herman L.; Muleri, Fabio; Negro, Michela; Jorstad, Svetlana G.; Agis-Gonzalez, Beatriz; Agudo, Ivan; Bonnoli, Giacomo; Bernardos, Maria, I; Casanova, Victor; Garcia-Comas, Maya; Husillos, Cesar; Marchini, Alessandro; Sota, Alfredo; Kouch, Pouya M.; Lindfors, Elina; Borman, George A.; Kopatskaya, Evgenia N.; Larionova, Elena G.; Morozova, Daria A.; Savchenko, Sergey S.; Vasilyev, Andrey A.; Zhovtan, Alexey, V; Casadio, Carolina; Escudero, Juan; Myserlis, Ioannis; Hales, Antonio; Kameno, Seiji; Kneissl, Ruediger; Messias, Hugo; Nagai, Hiroshi; Blinov, Dmitry; Bourbah, Ioakeim G.; Kiehlmann, Sebastian; Kontopodis, Evangelos; Mandarakas, Nikos; Romanopoulos, Stylianos; Skalidis, Raphael; Vervelaki, Anna; Masiero, Joseph R.; Mawet, Dimitri; Millar-Blanchaer, Maxwell A.; Panopoulou, Georgia, V; Tinyanont, Samaporn; Berdyugin, Andrei, V; Kagitani, Masato; Kravtsov, Vadim; Sakanoi, Takeshi; Imazawa, Ryo; Sasada, Mahito; Fukazawa, Yasushi; Kawabata, Koji S.; Uemura, Makoto; Mizuno, Tsunefumi; Nakaoka, Tatsuya; Akitaya, Hiroshi; Gurwell, Mark; Rao, Ramprasad; Di Lalla, Niccolo; Cibrario, Nicolo; Donnarumma, Immacolata; Kim, Dawoon E.; Omodei, Nicola; Pacciani, Luigi; Poutanen, Juri; Tavecchio, Fabrizio; Antonelli, Lucio A.; Bachetti, Matteo; Baldini, Luca; Baumgartner, Wayne H.; Bellazzini, Ronaldo; Bianchi, Stefano; Bongiorno, Stephen D.; Bonino, Raffaella; Brez, Alessandro; Bucciantini, Niccolo; Capitanio, Fiamma; Castellano, Simone; Ciprini, Stefano; Costa, Enrico; De Rosa, Alessandra; Del Monte, Ettore; Di Marco, Alessandro; Doroshenko, Victor; Dovciak, Michal; Enoto, Teruaki; Evangelista, Yuri; Fabiani, Sergio; Ferrazzoli, Riccardo; Garcia, Javier A.; Gunji, Shuichi; Hayashida, Kiyoshi; Heyl, Jeremy; Iwakiri, Wataru; Karas, Vladimir; Kitaguchi, Takao; Kolodziejczak, Jeffery J.; Krawczynski, Henric; La Monaca, Fabio; Latronico, Luca; Maldera, Simone; Manfreda, Alberto; Marin, Frederic; Marinucci, Andrea; Massaro, Francesco; Matt, Giorgio; Mitsuishi, Ikuyuki; Ng, C-Y; O'Dell, Stephen L.; Oppedisano, Chiara; Papitto, Alessandro; Pavlov, George G.; Peirson, Abel L.; Pesce-Rollins, Melissa; Petrucci, Pierre-Olivier; Pilia, Maura; Possenti, Andrea; Ramsey, Brian D.; Rankin, John; Ratheesh, Ajay; Romani, Roger W.; Sgro, Carmelo; Slane, Patrick; Soffitta, Paolo; Spandre, Gloria; Tamagawa, Toru; Taverna, Roberto; Tawara, Yuzuru; Tennant, Allyn F.; Thomas, Nicholas E.; Tombesi, Francesco; Trois, Alessio; Tsygankov, Sergey; Turolla, Roberto; Vink, Jacco; Weisskopf, Martin C.; Wu, Kinwah; Xie, Fei; Zane, Silvia.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., Blazars are a class of jet-dominated active galactic nuclei with a typical double-humped spectral energy distribution. It is of common consensus that the synchrotron emission is responsible for the low frequency peak, while the origin of the high frequency hump is still debated. The analysis of X-rays and their polarization can provide a valuable tool to understand the physical mechanisms responsible for the origin of high-energy emission of blazars. We report the first observations of BL Lacertae (BL Lac) performed with the Imaging X-ray Polarimetry Explorer, from which an upper limit to the polarization degree ΠX < 12.6% was found in the 2–8 keV band. We contemporaneously measured the polarization in radio, infrared, and optical wavelengths. Our multiwavelength polarization analysis disfavors a significant contribution of proton-synchrotron radiation to the X-ray emission at these epochs. Instead, it supports a leptonic origin for the X-ray emission in BL Lac. © 2022. The Author(s). Published by the American Astronomical Society., The Imaging X-ray Polarimetry Explorer (IXPE) is a joint US and Italian mission. The US contribution is supported by the National Aeronautics and Space Administration (NASA) and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI) through contract ASI-OHBI-2017-12-I.0, agreements ASI-INAF-2017-12-H0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC), and by the Istituto Nazionale di Astrofisica (INAF) and the Istituto Nazionale di Fisica Nucleare (INFN) in Italy. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF, and INFN) and distributed with additional software tools by the High-Energy Astrophysics Science Archive Research Center (HEASARC), at NASA Goddard Space Flight Center (GSFC). We acknowledge financial support from ASI-INAF agreement n. 2022-14-HH.0. The research at Boston University was supported in part by National Science Foundation grant AST-2108622 and NASA Swift Guest Investigator grant 80NSSC22K0537. This research has made use of data from the RoboPol program, a collaboration between Caltech, the University of Crete, IA-FORTH, IUCAA, the MPIfR, and the Nicolaus Copernicus University, which was conducted at Skinakas Observatory in Crete, Greece. The IAA-CSIC coauthors acknowledge financial support from the Spanish "Ministerio de Ciencia e Innovacion" (MCINN) through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofísica de Andalucía-CSIC (SEV-2017-0709). Acquisition and reduction of the POLAMI, TOP-MAPCAR, and OSN data was supported in part by MICINN through grants AYA2016-80889-P and PID2019-107847RB-C44. The POLAMI observations were carried out at the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). This Letter makes use of the following ALMA director's discretionary time data under proposal ESO#2021.A.00016.T. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada), MOST, and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. Some of the data reported here are based on observations obtained at the Hale Telescope, Palomar Observatory as part of a continuing collaboration between the California Institute of Technology, NASA/JPL, Yale University, and the National Astronomical Observatories of China. This research made use of Photutils, an Astropy package for detection and photometry of astronomical sources (Bradley et al. 2019). G.V.P. acknowledges support by NASA through the NASA Hubble Fellowship grant #HST-HF2-51444.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. The data in this study include observations made with the Nordic Optical Telescope, owned in collaboration by the University of Turku and Aarhus University, and operated jointly by Aarhus University, the University of Turku, and the University of Oslo, representing Denmark, Finland, and Norway, the University of Iceland and Stockholm University at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. The data presented here were obtained in part with ALFOSC, which is provided by the Instituto de Astrofísica de Andalucía (IAA) under a joint agreement with the University of Copenhagen and NOT. E.L. was supported by Academy of Finland projects 317636 and 320045. Part of the French contribution is supported by the Scientific Research National Center (CNRS) and the French Spatial Agency (CNES). Some of the data are based on observations collected at the Observatorio de Sierra Nevada, owned and operated by the Instituto de Astrofísica de Andalucía (IAA-CSIC). Further data are based on observations collected at the Centro Astronómico Hispano-Alemán (CAHA), operated jointly by Junta de Andalucía and Consejo Superior de Investigaciones Científicas (IAA-CSIC). D.B., S.K., R.S., and N. M. acknowledge support from the European Research Council (ERC) under the European Unions Horizon 2020 research and innovation program under grant agreement No. 771282. C.C. acknowledges support by the European Research Council (ERC) under the HORIZON ERC Grants 2021 program under grant agreement No. 101040021. The Dipol-2 polarimeter was built in cooperation by the University of Turku, Finland, and the Leibniz Institut für Sonnenphysik, Germany, with support from the Leibniz Association grant SAW-2011-KIS-7. We are grateful to the Institute for Astronomy, University of Hawaii, for the allocated observing time. A.H. acknowledges The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This work was supported by JST, the establishment of university fellowships toward the creation of science technology innovation; grant No. JPMJFS2129. This work was supported by Japan Society for the Promotion of Science (JSPS) KAKENHI grant Nos. JP21H01137. This work was also partially supported by Optical and Near-Infrared Astronomy Inter-University Cooperation Program from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan., With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001131-S).

In this paper, we present the form factor $$\gamma {\text{*}}\omega {{\pi }^{0}}$$ measurement in the virtual photon mass range 1 GeV < $$\sqrt {{{q}^{2}}} $$ < 2 GeV in the $${{e}^{ + }}{{e}^{ - }} \to \omega {{\pi }^{0}} \to {{\pi }^{ + }}{{\pi }^{ - }}{{\pi }^{0}}{{\pi }^{0}}$$ process. Measurements are based on the data acquired by the SND detector at the VEPP-2000 $${{e}^{ + }}{{e}^{ - }}$$ collider in Novosibirsk. The obtained form factor is approximated in the vector meson dominance (VMD) model. The joint fitting of the form factor obtained in the SND and NA60 experiments is also performed.

The process $$e^{+}e^{-}\to\eta\pi^{0}\gamma$$ is studied in the range of center-of-mass (c.m.) collision energies between 1.05 and 2.00 GeV on the basis of data corresponding to an integrated luminosity of 94.5 pb $${}^{-1}$$ that were accumulated in an experiment with the SND detector at the VEPP-2000 $$e^{+}e^{-}$$ collider. The cross section for this process was measured for the first time and was found to receive a dominant contribution from the mechanism of a transition through an $$\omega\eta$$ intermediate state. The cross section measured for the process $$e^{+}e^{-}\to\omega\eta\to\eta\pi^{0}\gamma$$ agrees with the results of earlier measurements in the channel $$e^{+}e^{-}\to\pi^{+}\pi^{-}\pi^{0}\eta$$ . At a level of 5.7 standard deviations (5.7 $$\sigma$$ ), it is established that the process $$e^{+}e^{-}\to\eta\pi^{0}\gamma$$ is not fully described by hadronic intermediate states of the $$VP$$ type. The cross section was measured for this missing contribution, which may be generated by radiative processes—for example, $$e^{+}e^{-}\to a_{0}(1450)\gamma$$ . It ranges from 15 to 20 pb over a broad energy interval extending from 1.3 to 1.9 GeV.

In an experiment with the SND detector at the VEPP-2000 $$e^{+}e^{-}$$ collider, the cross sections for the processes $$e^{+}e^{-}\to K^{+}K^{-}\pi^{0}$$ and $$e^{+}e^{-}\to\phi\pi^{0}$$ were measured at collision energies of $$\sqrt{s}=1.28{-}2.00$$ GeV in the center-of-mass frame. The results agree with the results of earlier measurements in the BABAR experiment and have a commensurate precision.

Using the SND detector, the process $$e^{+}e^{-}\to\pi^{+}\pi^{-}\pi^{0}$$ was studied in the energy range between 1.05 and 2.00 GeV. The respective measurement was performed on the basis of data accumulated in the experiments at the VEPP-2000 electron–positron collider throughout the runs of 2011 and 2012. Also, the invariant-mass spectra of the $$\pi^{+}\pi^{-}$$ and $$\pi^{\pm}\pi^{0}$$ combinations were analyzed in the energy range between 1.15 and 2 GeV. This resulted in finding an indication that the $$\omega(1680)$$ excited state decayed predominantly through the $$\rho^{\prime}\pi$$ intermediate state.

The results of searches for the process $$e^{+}e^{-}\to\eta^{\prime}\gamma$$ in an experiment with the SND detector at the VEPP-2000 electron–positron collider are presented. The data used in these searches and based on an integrated luminosity of about 87 pb $${}^{-1}$$ were accumulated at c.m. energies $$\sqrt{s}$$ between 1.15 and 2 GeV. The upper limits of $$\sigma_{\eta^{\prime}\gamma}

Polarimetry provides an avenue for probing the geometry and physical mechanisms producing optical radiation in many astrophysical objects, including stellar binary systems. We present the results of multiwavelength (BVR) polarimetric studies of a sample of historical black hole X-ray binaries, observed during their outbursts or in the quiescent (or near-quiescent) state. We surveyed both long- and short-period systems, located at different Galactic latitudes. We performed careful analysis of the interstellar polarization in the direction on the sources to reliably estimate the intrinsic source polarization. Intrinsic polarization was found to be small (5 per cent) intrinsic quiescent-state polarization with a blue spectrum. The absence of intrinsic polarization at the optical wavelengths puts constraints on the potential contribution of non-stellar (jet, hot flow, accretion disc) components to the total spectra of black hole X-ray binaries.

The observational signatures of black holes in x-ray binary systems depend on their masses, spins, accretion rate and the misalignment angle between the black hole spin and the orbital angular momentum. We present optical polarimetric observations of the black hole x-ray binary MAXI J1820+070, from which we constrain the position angle of the binary orbital axis. Combining this with previous determinations of the relativistic jet orientation axis, which traces the black hole spin, and the inclination of the orbit, we determine a lower limit of 40 deg on the spin-orbit misalignment angle. The misalignment has to originate from either the binary or black hole formation stage. If other x-ray binaries have similarly large misalignments, these would bias measurements of black hole masses and spins from x-ray observations., Comment: 31 pages, 9 figures

About half of white dwarfs (WDs) evolve to the DC state as they cool; the others become DQ or (temporarily?) DZ WDs. The recent magnetic survey of the local 20 pc volume has established a high frequency of magnetic fields among WDs older than 2-3 Gyr, demonstrating that in low- and average-mass WDs, the effects of magnetism become more common as they age, and the fields on average become stronger. However, the available statistics of WDs older than about 5 Gyr do not clearly establish how fields evolve beyond this age. We are carrying out a survey to clarify the occurrence of magnetism in DC-type WDs in order to better understand this late evolution. We use broadband filter polarimetry, arguably the most efficient way to detect magnetic fields in featureless WDs via continuum circular polarization. Here we report the discovery of a magnetic field in five DC WDs (of 23 observed), almost doubling the total sample of known magnetic WDs belonging to the DC spectral class., Accepted by A&A

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/)., Successful observations of the seven predicted bremsstrahlung flares from the unique bright blazar OJ 287 firmly point to the presence of a nanohertz gravitational wave (GW) emitting supermassive black hole (SMBH) binary central engine. We present arguments for the continued monitoring of the source in several electromagnetic windows to firmly establish various details of the SMBH binary central engine description for OJ 287. In this article, we explore what more can be known about this system, particularly with regard to accretion and outflows from its two accretion disks. We mainly concentrate on the expected impact of the secondary black hole on the disk of the primary on 3 December 2021 and the resulting electromagnetic signals in the following years. We also predict the times of exceptional fades, and outline their usefulness in the study of the host galaxy. A spectral survey has been carried out, and spectral lines from the secondary were searched for but were not found. The jet of the secondary has been studied and proposals to discover it in future VLBI observations are mentioned. In conclusion, the binary black hole model explains a large number of observations of different kinds in OJ 287. Carefully timed future observations will be able to provide further details of its central engine. Such multi-wavelength and multidisciplinary efforts will be required to pursue multi-messenger nanohertz GW astronomy with OJ 287 in the coming decades. © 2021 by the authors. Licensee MDPI, Basel, Switzerland., L.D. and A.G. acknowledge the support of the Department of Atomic Energy, Government of India, under project identification # RTI 4002. A.G. is grateful for the financial support and hospitality of the Pauli Center for Theoretical Studies and the University of Zurich. S.Z. acknowledge the grant NCN 2018/29/B/ST9/01793. R.H. acknowledges support by GACR grant 13-33324S and by the MSMT Mobility project 8J18AT036., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

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.

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 − , n n ‾ , K + K − η , π + π − η , K S K L π 0 , π + π − π 0 η , π 0 γ , ω π 0 , and η → e + e − .

The cross section for the process e+e− → ηK+K− wasmeasured at c.m. energies in the range between 1.56 and 2.00 GeV in an experiment with the SND detector at the VEPP-2000 e+e− collider. The invariant-mass distribution of kaon pairs is consistent with the hypothesis that the transition through the ηφ intermediate state makes a dominant contribution to the transition in question.

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 − , π 0 γ , η π + π − π 0 and ω π 0 η have been studied.

This article considers issues related to information and analytics support of organization and management activities for the protection of critical information infrastructure (CII). The covered problem is of interest for large industrial enterprises (subjects of CII), therefore, there is a need to accumulate and process large data arrays that are of primary importance for ensuring information security. To meet the information needs arising while protecting CII, it is proposed to use the information-analytical system (IAS), created on the basis of the integrated database management system (IDMS) “CronosPro”. The scientific novelty of the work is that the newly created IAS allows to formalize and ensure the information needs of the security administrator at all stages of the protection of CII objects. An example of information and analytical support for activities related to the formation and operation of databases is given to illustrate the full range capabilities of IAS: the categorization of CII object, confidential information storage devices, and persons allowed to the confidential data. These databases greatly facilitate the definition of the actual awareness of employees of CII subject in the confidential information, as well as conducting checks of confidential paperwork. Since all the listed databases consist of similar and interrelated information objects (“Organization”, “CII object”, “Person”, “Action”, “Data Storage”, “Document”), IAS allows you to decide not only knowledge management but also information and logical tasks as well as to identify non-obvious connections (second-level connections) between information objects, which is especially important in the process of investigating computer incidents.

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 $e^+e^-\to\eta\pi^+\pi^-$, $e^+e^-\to\eta K^+K^-$, $e^+e^-\to K_SK_L\pi^0$ cross sections, and the preliminary results on study of the $e^+e^-\to\pi^+\pi^-$, $e^+e^-\to n\bar{n}$, $e^+e^-\to\pi^0\gamma$, and the upper limit for $\eta\to e^+e^-$ decay branching fraction

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.

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., Comment: 11 pages, 4 figures

Precise study of the hadrons production in \bm{e^+e^-}𝐞+𝐞− 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)}(𝐠−2) 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.

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.

The process e+e-→π0γ 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-→π0γ 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-→π0γ is studied for the first time.

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.

The sensitivity of the VEPP-2000 e + e − collider in the search for the rare decay η → e + e − has been studied. The inverse reaction e + e − → η 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 − → η in the decay mode η → π0π0π0. In the absence of background, a sensitivity to B(η → e + e −) of 10−6 can be reached during two weeks of VEPP-2000 operation. Such a sensitivity is higher than the current upper limit on B(η → e + e −) by a factor of 2.3.

The cross section for the e + e – → π+π–π0 process in the energy range 1.05–2.00 GeV has been measured using the data collected in the experiment with the Spherical Neutral Detector (SND) at the VEPP-2000 e + e – collider. The obtained results on the cross section are in good agreement with previous measurements by the SND at the VEPP-2M collider and BABAR, but have a better accuracy.

A survey of preliminary results of experiments with the SND detector at the VEPP-2000 e+e− collider in the energy range of \(\sqrt s \) = 1000–2000 MeV MeV is presented. The cross sections for the processes e+e− → π0π0γ, e+e− → π+π−π0π0, e+e− → π+π−π0, e+e− → π+π−η, and e+e− → \(p\bar p\) were measured. The measured cross sections agree with the results of earlier measurements but have a higher precision. The cross section for the process e+e− → ηγ in the energy range extending from 1.4 to 2 GeV was measured for the first time. The ratio GE/GM for the neutron was measured for the first time in the timelike region.

The ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}$ 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 $35\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ collected at the VEPP-2000 ${e}^{+}{e}^{\ensuremath{-}}$-collider. The obtained results are consistent with the previous most accurate data obtained in the BABAR experiment and have a comparable accuracy.

Latest results on study of processes of $e^+e^-$ annihilation into exclusive hadronic states at $\sqrt{s}$ < 2 GeV 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 $e^+e^-\to \pi^0 \gamma$ and $e^+e^-\to K^+ K^-$ cross sections, the first measurements of the $e^+e^-\to \omega \pi^0 \eta$ and $e^+e^-\to \pi^+ \pi^-\pi^0 \eta$ reactions and preliminary results of measurement of the $e^+e^-\to \pi^+ \pi^-$ cross section in energy range 0.5 < $\sqrt{s}$ < 0.9 GeV.

The e+e-→ηπ+π- cross section is measured at the Spherical Neutral Detector (SND) detector in the η decay mode η→3π0. The analysis is based on the data sample with an integrated luminosity of 32.7 pb-1 collected at the VEPP-2000 e+e- collider in the center-of-mass energy range s=1.075–2.000 GeV. The data obtained in the η→3π0 decay mode are found to be in agreement with the previous SND measurements in the η→γγ mode. Therefore the measurements in the two modes are combined.

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 e+e-→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.

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.

The process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\omega}\ensuremath{\eta}{\ensuremath{\pi}}^{0}$ is studied in the energy range 1.45--2.00 GeV using data with an integrated luminosity of $33\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ accumulated by the SND detector at the ${e}^{+}{e}^{\ensuremath{-}}$ collider VEPP-2000. The ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\omega}\ensuremath{\eta}{\ensuremath{\pi}}^{0}$ 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 ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\omega}\ensuremath{\eta}{\ensuremath{\pi}}^{0}$ is found to be $\ensuremath{\omega}{a}_{0}(980)$.