V. Zhulanov

The interference fragmentation function translates the fragmentation of a quark with a transverse projection of the spin into an azimuthal asymmetry of two final-state hadrons. In e+e- annihilation the product of two interference fragmentation functions is measured. We report nonzero asymmetries for pairs of charge-ordered pi+pi- pairs, which indicate a significant interference fragmentation function in this channel. The results are obtained from a 672 fb-1 data sample that contains 711 \times 106 pi+pi- pairs and was collected at and near the ?(4S) resonance, with the Belle detector at the KEKB asymmetric-energy e+e- collider.

A new version of fast, parallax-free, one-coordinate X-ray detector OD-3M destined for X-ray diffraction experiments is presented. The construction, basic principles of operation, results of the test with isotopic source Fe55 and X-ray beam test are being discussed.

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.

We present the analysis of all KEDR data on the determination of J/ψ and ψ(2S) masses. The data comprise six scans of J/ψ and seven scans of ψ(2S) which were performed at the VEPP-4M e+e− collider in 2002–2008. The beam energy was determined using the resonance depolarization method. The detector and accelerator conditions during scans were very different that increases the reliability of the averaged results. The analysis accounts for partial correlations of systematic uncertainties on the masses. The following mass values were obtained:MJ/ψ=3096.900±0.002±0.006 MeV,Mψ(2S)=3686.099±0.004±0.009 MeV. These results supersede our previous measurements published in 2003 and 2012.

Using the KEDR detector at the VEPP-4M $e^+e^-$ collider, we have measured the values of $R_{\text{uds}}$ and $R$ at seven points of the center-of-mass energy between 3.12 and 3.72 GeV. The total achieved accuracy is about or better than $3.3\%$ at most of energy points with a systematic uncertainty of about $2.1\%$. At the moment it is the most accurate measurement of $R(s)$ in this energy range.

We report the final results of a study of the \psi(3770) meson using a data sample collected with the KEDR detector at the VEPP-4M electron-positron collider. The data analysis takes into account the interference between the resonant and nonresonant $D\bar{D}$ production, where the latter is related to the nonresonant part of the energy-dependent form factor $F_D$. The vector dominance approach and several empirical parameterizations have been tried for the nonresonant $F_D^{\NR}(s)$. Our results for the mass and total width of \psi(3770) are M = 3779.2 ^{+1.8}_{-1.7} ^{+0.5}_{-0.7} ^{+0.3}_{-0.3} MeV, \Gamma =24.9 ^{+4.6}_{-4.0} ^{+0.5}_{-0.6} ^{+0.2}_{-0.9} MeV, where the first, second and third uncertainties are statistical, systematic and model, respectively. For the electron partial width two possible solutions have been found: (1) \Gamma_{ee} = 154 ^{+79}_{-58} ^{+17}_{-9} ^{+13}_{-25} eV, (2) \Gamma_{ee} = 414 ^{+72}_{-80} ^{+24}_{-26} ^{+90}_{-10} eV. Our statistics are insufficient to prefer one solution to another. The solution (2) mitigates the problem of non-$D\bar{D}$ decays but is disfavored by potential models. It is shown that taking into account the resonance--continuum interference in the near-threshold region affects resonance parameters, thus the results presented can not be directly compared with the corresponding PDG values obtained ignoring this effect.

A high-precision determination of the main parameters of the ψ(2S) resonance has been performed with the KEDR detector at the VEPP-4M e+e− collider in three scans of the ψ(2S)–ψ(3770) energy range. Fitting the energy dependence of the multihadron cross section in the vicinity of the ψ(2S) we obtained the mass valueM=3686.114±0.007±0.011−0.012+0.002 MeV and the product of the electron partial width by the branching fraction into hadronsΓee×Bh=2.233±0.015±0.037±0.020 keV. The first and second uncertainties are statistical and systematic, respectively. The third uncertainty quoted is an estimate of the model dependence of the result due to assumptions on the interference effects in the cross section of the single-photon e+e− annihilation to hadrons explicitly considered in this work. Implicitly, the same assumptions were employed to obtain the charmonium leptonic width and the absolute branching fractions in many experiments. Using the result presented and the world average values of the electron and hadron branching fractions, one obtains the electron partial width and the total width of the ψ(2S):Γee=2.282±0.015±0.038±0.021 keV,Γ=296±2±8±3 keV. These results are consistent with and more than two times more precise than any of the previous experiments.

Methods of dynamic imaging of explosions at a synchrotron radiation (SR) beam and small-angle X-ray scattering experiments with exploding samples are being developed in the Siberian Synchrotron Radiation Center (SSRC) at the Budker Institute of Nuclear Physics for more than fifteen years. The detector for imaging of explosions (DIMEX) was developed for these purposes and successfully operating at the beam line 0 at the VEPP-3 storage ring and at the beam line 8 at the VEPP-4 M storage ring. The DIMEX is based on gas technology and allow to measure SR flux as a function of position and time with spatial resolution of ∼200 μm (FWHM), maximum frame rate of 2 MHz and time resolution of ∼80 ns. Maximum value of the SR flux that can be measured by the present detector corresponds to ∼5000 photons/(channel*bunch) (20 keV average energy, channel area 0.1x0.5 mm2, bunch revolution frequency 4 MHz). Maximum number of frames that can be stored in the present detector is 32 and the number of channels with 0.1 mm width is 512. In order to significantly improve the precision of data obtained by the DIMEX an upgrade of the detector has been started. The electronics of the gaseous version of the detector has been changed such that the new detector is able to operate with frame rate of 8 MHz and store data in up to 100 frames. A new ASIC was developed for this purpose called DMXG64A that includes 64 channels with low noise integrator and 100 analogue memory cells in each channel. Input charge can be stored to and read out from analogue cells with maximum frequency 10 MHz. This new version of the detector is called the DIMEX-G and is planned to be used at the VEPP-3 storage ring and for SAXS studies at the VEPP-4 M storage ring. For imaging of explosions at the beam line 8 at the VEPP-4 M storage ring, where SR flux is expected to be about 10-100 times higher than at the VEPP-3, a new detector based on Si micro-strip technology is being developed. Si micro-strip sensors with special design have been manufactured by Hamamatsu Photonics company. Each sensor contains 1024 30 mm long strips with 50 μm pitch. The sensor thickness is 320 μm and it will be positioned at an angle of 1.7 degrees with respect to the SR beam plane in order to get effective Si thickness along the beam close to 10 mm. The new detector called DIMEX-Si will have spatial resolution of 50 μm (FWHM) and time resolution close to 10 ns. The new ASIC is under development for this project that will allow to operate with the frame rate of 50 MHz and record maximum charge that corresponds to the flux close to 106 photons/(chan*bunch), i.e. about 100 times higher than with present detector.

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 present work continues a series of the KEDR measurements of the $R$ value that started in 2010 at the VEPP-4M $e^+e^-$ collider. By combining new data with our previous results in this energy range we measured the values of $R_{\text{uds}}$ and $R$ at nine center-of-mass energies between 3.08 and 3.72 GeV. The total accuracy is about or better than $2.6\%$ at most of energy points with a systematic uncertainty of about $1.9\%$. Together with the previous precise $R$ measurement at KEDR in the energy range 1.84-3.05 GeV, it constitutes the most detailed high-precision $R$ measurement near the charmonium production threshold.

Status of several projects under development in Budker INP with GEM-based detectors for synchrotron radiation imaging and particle tracking is reviewed. These are namely: the detector for imaging of explosions(DIMEX) at SR beam, the detector for WAXS studies at SR beam (OD4), the triple-GEM detectors for the tagging system of KEDR experiment at VEPP-4M collider and the triple-GEM detectors for the tagging system of Deuteron experiment at VEPP-3 storage ring.

We present a study of the inclusive photon spectrum from 6.3 million J/ψ decays collected with the KEDR detector at the VEPP-4M e + e - collider. We measure the branching fraction of the radiative decay J/ψ → η c γ, η c width and mass. Taking into account an asymmetric photon line shape we obtain: M η c = (2978.1 ± 1.4 ± 2.0) MeV/c 2 , Γ η c = (43.5 ± 5.4 ± 15.8) MeV, [Formula: see text].

The series of high-rate and high spatial resolution gaseous detectors for diffraction studies and X-ray imaging at SR beam developed in the Budker INP is reviewed. The detectors are based on wire and micro-pattern gas technologies and provide spatial resolution at the level of 0.1 mm together with rate capability in the range from 10 MHz per detector to 10 10 Hz=channel.

The tagging system (TS) of the KEDR detector is designed for study of two-photon interactions on the VEPP-4M electron-positron collider. The upgrade of the TS was completed and 8 triple-GEM detectors were added to the system with a single detector sensitive area up to 250*100 mm2, a spatial resolution in the beam orbit plane close to 70 μm and a small angle stereo readout providing a resolution of around 200 μm in perpendicular direction. The triple-GEM detectors were included into the KEDR DAQ system, and since the beginning of the 2010-2011 season they have demonstrated stable operation at a gas gain of 20000–40000 and efficiency of 95–97%. The new detectors will allow performing background suppression and improving the energy resolution of the system.

Using the inclusive photon spectrum based on a data sample collected at the J/ψ peak with the KEDR detector at the VEPP-4M e+e− collider, we measured the rate of the radiative decay J/ψ→γηc as well as ηc mass and width. Taking into account an asymmetric photon lineshape we obtained Γγηc0=2.98±0.18−0.33+0.15keV, Mηc=2983.5±1.4−3.6+1.6MeV/c2, Γηc=27.2±3.1−2.6+5.4MeV.

The main purpose of the beamline design – realization of experiments using explosive charges up to 200 grams of TNT equivalent. To achieve this goal is necessary to use a of hard range of photons in the region of 30-60 keV. Additional requirement - the development of a powerful explosion chamber, and very fast one coordinate detector DIMEX. The fist detonation experiments was made with explosive 40 mm diameter. Test WAXS experiments was made and time resolution of 73 ps was received. SAXS/WAXS experiments was made at accelerators complex VEPP-3/VEPP-4.

The described detector for imaging of explosions (DIMEX) has been designed for the studies of fast processes (explosions, combustion) at synchrotron radiation (SR) beam. DIMEX has been in operation on the SR beam-line on the VEPP-3 electron ring at Budker INP since 2002. DIMEX is based on a one-coordinate gas ionization chamber filled with a Xe–CO2 (3:1) mixture at 7 atm and active Frisch-grid made of a Gas Electron Multiplier (GEM). The detector has a spatial resolution of 0.2 mm and dynamic range of ∼100, which allows one to achieve a signal measurement precision of a few percent. The future possibility to install a similar detector on the SR beam-line on the VEPP-4 electron ring is discussed and the last version of the detector is described.

Status of the upgrade of the tagging system of KEDR experiment at VEPP-4M is described. Triple-GEM detectors have been added to eight coordinate stations of the system. These detectors will improve momentum resolution of the system and will allow effective rejection of the background of single Bremsstrahlung events. Main parameters of the triple-GEM detectors have been measured at the cosmic ray setup. Efficiency reaches 98% and spatial resolution in the direction of the beam orbit plane is 73μm (standard deviation).

In situ imaging of explosions allows to study material properties under very high pressures and temperatures. Synchrotron radiation (SR) is a powerful tool for such studies because of its unique time structure. Flashes of X-rays from individual bunches in a storage ring are so short that an object under study does not move more than 1–10 μm during exposure. If a detector is able to store images synchronously with bunches of an SR source the time resolution of such method will be determined by the duration of SR flash from individual bunch. New beam line at the VEPP-4M storage ring will allow to get X-Ray flux from each bunch close to 106 photons/channel where channel area is 0.05×0.5 mm2 and average beam energy is about 30 keV. Bunches in the machine can be grouped into trains with 20 ns time gap. In order to meet these requirements a new detector development was started based on Si microstrip technology. The detector with a new dedicated front-end chip will be able to record images with maximum signal equivalent to 106 photons/channel, with signal to noise ratio of ∼103, spatial resolution of 50 μm and maximum frame rate of 50 MHz. The detector has to drive very high peak and average currents without affecting the front-end chip, therefore a specific design of Si sensor should be developed. The front-end chip has to provide signal measurements with the dynamic range of about 104 or more and recording of the signal to an analogue memory with the rate of 50 MHz. The concept of such detector is discussed in the paper. The results of the simulations of the main detector parameters and the results of the first measurements with the prototype sensors are presented.

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.

Investigation of fast dynamic processes (explosions) with the help of synchrotron radiation allows to understand properties of matter at very high temperatures and pressures. Detector for such studies has to be able to detect X-ray photons from each electron bunch separately with position resolution of about 0.1 mm.The prototype of detector for imaging of explosions at SR beam (DIMEX) is described in the paper. Spatial resolution of ∼300 μm (FWHM) and time resolution of ∼100 ns is demonstrated with SR beam from 2 T wiggler at VEPP-3 and electron beam energy of 2 GeV.Results of the first experiments on projective imaging and small angle scattering (SAXS) are presented.

The described detector for imaging of explosions (DIMEX) has been in operation on the synchrotron radiation (SR) beam-line on the VEPP-3 electron ring at Budker INP since 2002. DIMEX is based on a one-coordinate gas ionization chamber filled with a Xe-CO2(3:1) mixture at 7atm and active Frisch-grid made of a Gas Electron Multiplier (GEM). The detector has a spatial resolution of 0.2mm and dynamic range of ∼100, which allows one to achieve a signal measurement precision of a few percent. The frame rate can be tuned up to 8 MHz (125 ns per image) and as many as 32 images can be stored in one shot. At present DIMEX is used with the X-ray beam from a 2T wiggler with an average energy of 20 keV. The future possibility to install a similar detector on the SR beam-line on the VEPP-4 electron ring is discussed.

This paper describes the experimental studies of the formation of nano-diamonds during detonation of TNT/RDX 50/50 mixture with small-angle x-ray scattering (SAXS) method at a synchrotron radiation beam on VEPP-3 accelerator. A new experimental method with introduction of nano-diamonds into the explosive has been applied. Inclusion of the diamonds obtained after detonation into the TNT and RDX explosives allows modelling of the case of instant creation of nano-diamonds during detonation.

The products of the electron width of the J/\psi meson and the branching fraction of its decays to the lepton pairs were measured using data from the KEDR experiment at the VEPP-4M electron-positron collider. The results are \Gamma_{ee}(J/\psi)*Br(J/\psi->e^+e^-)=(0.3323\pm0.0064\pm0.0048) keV, \Gamma_{ee}(J/\psi)*Br(J/\psi->\mu^+\mu^-)=(0.3318\pm0.0052\pm0.0063) keV. Their combinations \Gamma_{ee}\times(\Gamma_{ee}+\Gamma_{\mu\mu})/\Gamma=(0.6641\pm0.0082\pm0.0100) keV, \Gamma_{ee}/\Gamma_{\mu\mu}=1.002\pm0.021\pm0.013 can be used to improve theaccuracy of the leptonic and full widths and test leptonic universality. Assuming e\mu universality and using the world average value of the lepton branching fraction, we also determine the leptonic \Gamma_{ll}=5.59\pm0.12 keV and total \Gamma=94.1\pm2.7 keV widths of the J/\psi meson.

The masses of the neutral and charged D mesons have been measured with the KEDR detector at the VEPP-4M electron–positron collider:MD0=1865.30±0.33±0.23MeV,MD+=1869.53±0.49±0.20MeV.

This work presents the results of experiments using synchrotron radiation from the VEPP-4M accelerator complex at Budker Institute of Nuclear Physics. Dynamic of small-angle X-ray scattering of synchrotron radiation was implemented on the synchrotron radiation beamline 8-b. Here given beam parameters and described elements of the station and detector system. The distance from the axis of the explosive charge to the detector was 3432 mm. The strip size of the detector DIMEX was 0.1 mm. Thus, a single channel of the detector DIMEX in these experiments corresponded to the scattering angle 2θ: 1 detector channel = 0.02914 mrad. The SAXS measurement technique on this station enables detection of nanoparticles ranging in size from 2 nm to 200 nm with exposure time 73 ps for one frame. It is possible to record 100 frames with interval 100 ns. In this work used TNT with 30 mm in diameter and 55 mm in length. Ultra fine diamonds of 2 nm size was detected behind the detonation front, after that the average size of particles increases up to 5–6 nm during few microseconds.

An upgrade of a special system to tag scattered electrons from two-photon processes, based on triple-GEM detectors, is described. The system is intended for the experiments at the VEPP-4M storage ring. Tests of the detector prototype with two gas mixtures confirm the feasibility of the chosen upgrade layout.

Detector for the studies of very fast processes (explosions, detonation waves, etc.) at a synchrotron radiation (SR) beam is described. The main feature of such device is to be able to detect SR photons from each electron bunch separately with the position resolution of about 0.1 mm. The first prototype of the detector for imaging of explosions demonstrated spatial resolution of ∼200μ, time resolution of ∼50ns and dynamic range of ∼100 with white SR beam from 2 T wiggler and electron beam energy of 2 GeV. Results of the first experiments on projective and SAXS imaging are presented.

The electromagnetic calorimeter of the BELLE II detector for experiments at Super B-factory SuperKEKB is briefly described. The project of the calorimeter upgrade to meet severe background conditions expected at the upgraded KEK B factory is presented.

Cascaded Gas Electron Multipliers (GEM) allow to construct detectors for charge particles tracking with high spatial resolution and rate capability. Such detectors can withstand high background fluxes up to 105 particles/mm2/s and determine track coordinates with precision of 50 – 70 micron. These remarkable features of GEM govern the use of this technology in a number of experiments at the Budker Institute of Nuclear Physics. In this paper the current status and progress in the performance studies and the development of the detectors for the tagging system of the KEDR experiment at the VEPP-4M collider and for the DEUTERON facility at the VEPP-3 storage ring will be covered. The new proposals for the upgrade of tracking and trigger system of the CMD-3 detector, the tracking detectors for the extracted beam from the VEPP-4M storage ring and the tracking detectors for the polarimeter at the VEPP-4M with the use of GEM technology will be discussed.

The status of the experiment on the precise τ lepton mass measurement running at the VEPP-4M collider with the KEDR detector is reported. The mass value is evaluated from the τ+τ− cross section behavior around the production threshold. The preliminary result based on 15.2 pb−1 of data is mτ=1776.69−0.19+0.17±0.15MeV.

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.

Micro-pattern gaseous detectors (MPGDs) allow operation at very high background particle flux with high efficiency and spatial resolution. This combination of parameters determines the main application of these detectors in particle physics experiments: precise tracking in the areas close to the beam and in the end-cap regions of general-purpose detectors. MPGDs of different configurations have been developed and are under development for several experiments in the Budker INP. The system of eight two-coordinate detectors based on a cascade of Gas Electron Multipliers (GEM) is working in the KEDR experiment at the VEPP-4M collider in the tagging system that detects electrons and positrons that lost their energy in two-photon interactions and left the equilibrium orbit due to a dedicated magnetic system. Another set of cascaded GEM detectors is developed for the almost-real Photon Tagging System (PTS) of the DEUTRON facility at the VEPP-3 storage ring. The PTS contains three very light detectors with very high spatial resolution (below 50 μm). Dedicated detectors based on cascaded GEMs are developed for the extracted electron beam facility at the VEPP-4M collider. These devices will allow precise particle tracking with minimal multiple scattering due to very low material content. An upgrade of the coordinate system of the CMD-3 detector at the VEPP-2000 collider is proposed on the basis of the resistive micro-WELL (μ-rWELL). A research activity on this subject has just started.

We present a study of the inclusive photon spectra from 5.9 million J/ψ decays collected with the KEDR detector at the VEPP-4M e+e− collider. We measure the branching fraction of radiative decay J/ψ → ηcγ, ηc width and mass. Our preliminary results are: M(ηc) = 2979.4±1.5±1.9 MeV/c2, Γ(ηc) = 27.8±5.1±3.3 MeV, Γ(J/ψ→ ηcγ) = (2.34±0.15±0.40)%.

Gaseous Electron Multiplier(GEM)-based position sensitive detectors are used and planned to be used in several experiments in the Budker Institute of Nuclear Physics. At present eight triple-GEM detectors are installed in the KEDR experiment at the VEPP-4M collider where they operate in the tagging system measuring momenta of electrons and positrons after two-photon interactions. Several triple-GEM detectors made of very light components are planned to be installed in the DEUTERON experiment at the VEPP-3 storage ring. The first detector of this type is assembled and tested with dedicated electronics. We plan also to build large cylindrical GEM-based detector with two layers of cylindrical triple-GEMs of 60 cm inner diameter. This project is now discussed for the Cryogenic Magnetic Detector (CMD-3) at the VEPP-2000 collider.

In this work we present experimental data on measuring distributions of small- angle X-ray scattering (SAXS) during cast trinitrotoluene (TNT) detonation of 30 and 40 mm in diameter. Dynamics of average size of condensed carbon nanoparticle inkreases has been restored from experimental SAXS data. The work was carried out at the SYRAFEEMA (Synchrotron Radiation Facility for Exploring Energetic Materials) station at accelerator complex VEPP- 4M (Budker Institute of Nuclear Physics). We observe minimal size of particles of order of 2 nm directly behind the detonation front. Later, the average size of carbon nanoparticles increases within 4-12 μs and reach values of 6 nm.

Hihg-power flows of plasma cause mechanical destruction of materials via non-uniform deformation and stresses. The possibility of synchrotron radiation scattering diagnostics of deformation is discussed. The experiments at the new scattering station “Plasma” on VEPP-4M demonstrated the measurements of change in the diffraction angle during pulsed heating.

The paper presents an overview of plasma-material interaction studies at the Siberian Synchrotron and Terahertz Radiation Centre. The measurements of recrystallization and surface texturing are demonstrated. The growth of grain size after the exposure by electron beam was detected using two-dimensional diffractometry. The orientation of crystal structure was detected in the tungsten irradiated by deuterium plasma. The residual stresses in irradiated tungsten were measured. The predicted structure of deformations after pulsed heat load is confirmed. First in-situ experiments confirmed the presence of crystal plane rotation effect during a pulsed heat load.

The jet structure from metal surface initiated by shock wave was investigated by small angle X-ray scattering (SAXS) technique for the first time. In these experiments used synchrotron radiation from the colliders VEPP-4. The beamlines 0-b at VEPP-3 and 8-b at VEPP-4 were used. These technique enables reliable detection of metal nanoparticles of 4 - 200 nm size with exposure time 73 ps (at VEPP-4) for one frame and interval 125 ns. It was found that jet from tin and tantalum foils impacted by pressed HMX gives a strong SAXS signal. This means that dust in jet contain nanoparticles. SAXS curve processing gives the nanoparticles size - about 100 nm. The flow of micro- and nanoparticles was about 4% by weight. The SAXS signal decreases with the usage of a less strong high explosive (plasticized PETN). It was found for the first time that the dust in jet has fine structure of density distribution which changes with time.

Investigations of fast dynamic processes with the help of synchrotron radiation allow an understanding of the properties of short-lifetime states of materials at very high temperatures and pressures. Detectors for such studies have to be able to detect X-ray photons from each electron bunch separately with a position resolution of about 0.1 mm. A prototype of a detector (DIMEX) for the imaging of explosions at a synchrotron radiation beam is described here. A spatial resolution of approximately 300 micro m and a time resolution of approximately 100 ns is demonstrated with a synchrotron radiation beam from the VEPP-3 2 T wiggler at an electron beam energy of 2 GeV. Results of the first projective imaging and SAXS experiments are presented.

We report results of a search for narrow resonances in e+ e- annihilation at center-of-mass energies between 1.85 and 3.1 GeV performed with the KEDR detector at the VEPP-4M e+ e- collider. The upper limit on the leptonic width of a narrow resonance Gamma(R -> ee) Br(R -> hadr) < 120 eV has been obtained (at 90 % C.L.).

The designed luminosity of the Belle detector after its upgrade (Belle II experiment) is 40 times higher than the maximum reached before its shutdown for an upgrade. This necessitates an upgrade of the Belle DAQ system together with the upgrade of many detector's subsystems. In this paper the upgrade of the Belle Electromagnetic calorimeter (ECL) electronics is described.

A specialized integrated circuit was developed for the readout of signal from coordinate detectors of different types, including gas micro-pattern detectors and silicon microstrip detectors. The ASIC includes 64 channels, each containing a low-noise charge-sensitive amplifier with a connectable feedback capacitor and resistor, and fast reset of the feedback capacitor. Each channel of the ASIC also contains 100 cells of analogue memory where the signal can be stored at a rate of 10 MHz. The pitch of input pads is 50 μm and the chip size is 5× 5 mm2. The equivalent noise charge of the ASIC channel is about 2000 electrons with 10 pF capacitance at the input and maximal signal before saturation corresponds to 2× 106 electrons. The first application for this ASIC is the detector for imaging of explosions at a synchrotron radiation beam (DIMEX), where it has to substitute the old and slower APC128 ASIC. The full-size electronics including 8 ASICs for 512 channels was assembled and tested.

Time resolved small angle x-ray scattering (SAXS) experiments on detonating high explosives have been conducted at the Lavrentyev Institute of Hydrodynamics and the Budker Institute of Nuclear Physics. The purpose of these experiments is to measure the SAXS patterns behind the detonation front and restore the dynamics of a carbon condensation process. The deficiency of the experimental data hinders the development of detonation models. In this work we present a new method to restore the dynamic of carbon condensation from time resolved SAXS patterns.

A one-coordinate gaseous detector of soft X-ray photons for WAXS experiments has been designed. The detector operates in counting mode and is based on multi-stage Gas Electron Multiplier (GEM). The main characteristics have been measured with the prototype having 0.4 mm pitch of readout strips. The simulation has been performed demonstrating the possibility of getting required spatial resolution with 0.2 mm channel pitch. The full-scale detector with partially connected readout structure has been fabricated and made ready for operation.

The construction of the SuperKEKB electron-positron collider and upgrade of the Belle II spectrometer are going on at KEK aiming at high precision measurements in bottom, charm and tau flavor sectors. We describe a replacement of the electronics for the CsI(Tl) crystal calorimeter with PIN-PD readout to match the luminosity increase up to 8 × 1035 cm−2s−1 at maximum. A plan to replace CsI(Tl) crystals with pure CsI in the endcaps is also mentioned.

Status of the development of a one-coordinate gaseous detector of soft X-ray photons for wide-angle X-ray scattering (WAXS) studies is discussed. The detector operates in a counting mode and is based on a multi-stage Gas Electron Multiplier (GEM). A full size detector has a 67∘ aperture at 350 mm from the source. Its readout multi-strip structure has 2048 strips with a 0.2 mm pitch. Main parameters of the detector have been measured with a 8 keV X-ray beam on the VEPP-3 synchrotron ring. A spatial resolution of 470μm (FWHM) has been demonstrated that will allow distinguishing diffraction spots at 0.1∘.

The Belle-II electromagnetic calorimeter inherited crystals and front-end electronics from the Belle detector, however the readout electronics was essentially modified. New electronics provides continuous digitization of the shaped signal followed by the signal wave form analysis with the further reconstruction of both, amplitude and time of the signal. The time information allows one to suppress background essentially. The algorithm, which is implemented in FPGA, is properly simulated. We implemented this algorithm to the simulation software and studied it with the MC background data. The procedure for the calibration of the response function has been developed and tested with the barrel counters using cosmic-ray data.

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 ratio of the electron and muon widths of the $J/\psi$ meson has been measured using direct $J/\psi$ decays in the KEDR experiment at the VEPP-4M electron-positron collider. The result $\Gamma_{ee}(J/\psi)/\Gamma_{\mu\mu}(J/\psi)=1.0022\pm0.0044\pm0.0048\ (0.65\%)$ is in good agreement with the lepton universality. The experience collected during this analysis will be used for a $J/\psi$ lepton width determination with up to 1% accuracy.

The paper presents current status of development of a specialized 64-channel integrated circuit (IC, ASIC) for front-end electronics of coordinate detectors in the Budker INP. The ASIC is produced using 180 nm process. During the recording phase the IC allows integration of short current pulses from strips of a coordinate sensor, and storing of up to 100 corresponding charge values in the analogue memory with minimum time interval of 100 ns. Maximum input charge is equal to 2×106 electrons, equivalent noise charge is ∼2.7×103 electrons.

A synchrotron radiation based technique is use to study the density distribution at the detonation front and its neighborhood for condensed explosives. Particular data are obtained on the structure of the detonation front in TNT, RDX, and an alloy of TNT with RDX; a comparison of the data with those obtained using different techniques confirms the correctness of the technique. It is concluded that adequate information on the structure of the chemical-reaction zone can be obtained for charges of small diameter. At the same time, it is shown that the Chapman-Jouguet parameters for such charges are far from their predicted values for an infinite medium. The results of the work, including those on the curvature of the detonation front in charges of small diameter, supplement the existing knowledge of the detonation transformation in condensed explosives.

New measurements of ψ(2S), ψ(3770) and D meson masses are presented. The results of the scans performed were used for determination of the products Γee×Γee/Γ for J/ψ and Γee×Γμμ/Γ for ψ(2S).

Time-resolved experiments on the diffraction of synchrotron radiation (SR) from crystalline materials provide information on the evolution of a material structure after a heat, electron beam or plasma interaction with a sample under study. Changes in the material structure happen within a microsecond scale and a detector with corresponding parameters is needed. The SR channel 8 of the VEPP-4M storage ring provides radiation from the 7-pole wiggler that allows to reach several tens photons within one μs from a tungsten crystal for the most intensive diffraction peak. In order to perform experiments that allow to measure the evolution of tungsten crystalline structure under the impact of powerful laser beam, a new detector is developed, that can provide information about the distribution of a scattered SR flux in space and its evolution in time at a microsecond scale. The detector is based on the silicon p-in-n microstrip sensor with DC-coupled metal strips. The sensor contains 1024 30 mm long strips with a 50 μm pitch. 64 strips are bonded to the front-end electronics based on APC128 ASICs. The APC128 ASIC contains 128 channels that consist of a low noise integrator with 32 analogue memory cells each. The integrator equivalent noise charge is about 2000 electrons and thus the signal from individual photons with energy above 40 keV can be observed. The signal can be stored at the analogue memory with 10 MHz rate. The first measurements with the beam scattered from a tungsten crystal with energy near 60 keV demonstrated the capability of this prototype to observe the spatial distribution of the photon flux with the intensity from below one photon per channel up to 0∼10 photons per channel with a frame rate from 10 kHz up to 1 MHz.

The development of the new spectrometric channel for the SND electromagnetic calorimeter is described. The time resolution of about 1 ns is achieved at an energy deposition in the calorimeter crystal of 100 MeV . The amplitude resolution is about 250 keV.

The paper presents current status of development of a specialized 64-channel integrated circuit (IC, ASIC) for front-end electronics of coordinate detectors in the Budker INP. The ASIC is produced using 180 nm process. During the recording phase the IC allows integration of short current pulses from strips of a coordinate sensor, and storing of up to 100 corresponding charge values in the analogue memory with minimum time interval of 100 ns. Maximum input charge is equal to 2×106 electrons, equivalent noise charge is ~2.7×103 electrons. Conversion of the data, stored in the analogue memory, to digital form is performed by an external ADC during the readout through an analogue multiplexer.

We present preliminary results of a new high-precision determination of the τ lepton mass performed with the KEDR detector at the VEPP-4M e+e− collider. These results are compared to two recent τ lepton mass measurements at Belle and BaBar.

We report results of experiments performed with the KEDR detector at the VEPP-4M e+e− collider. They include precise measurement of the D0 and D± meson masses, determination of the ψ(3770) resonance parameters, and a search for narrow resonances in e+e− annihilation at center-of-mass energies between 1.85 and 3.1 GeV.

The product of the electronic width of the $J/\psi$ meson and the branching fractions of its decay to hadrons and electrons has been measured using the KEDR detector at the VEPP-4M $e^+e^-$ collider. The obtained values are: $\Gamma_{ee}(J/\psi) = 5.550 \pm 0.056 \pm 0.089 \, \text{keV}, $ $\Gamma_{ee}(J/\psi) \cdot \mathcal{B}_\text{hadrons}(J/\psi) = 4.884 \pm 0.048 \pm 0.078 \, \text{keV}, $ $\Gamma_{ee}(J/\psi) \cdot \mathcal{B}_{ee}(J/\psi) = 0.3331 \pm 0.0066 \pm 0.0040 \, \text{keV}.$ The uncertainties shown are statistical and systematic, respectively. Using the result presented and the world-average value of the electronic branching fraction, one obtains the total width of the $J/\psi$ meson: $\Gamma = 92.94 \pm 1.83 \, \text{keV}.$ These results are consistent with the previous experiments.

When a metal plate is subjected to a strong shock impact, its free surface emits a flow of particles of different sizes (shock-wave "dusting"). Traditionally, the process of dusting is investigated by the methods of pulsed x-ray or piezoelectric sensor or via an optical technique. The particle size ranges from a few microns to hundreds of microns. The flow is assumed to include also finer particles, which cannot be detected with the existing methods yet. On the accelerator complex VEPP-3-VEPP-4 at the BINP there are two experiment stations for research on fast processes, including explosion ones. The stations enable measurement of both passed radiation (absorption) and small-angle x-ray scattering on synchrotron radiation (SR). Radiation is detected with a precision high-speed detector DIMEX. The detector has an internal memory of 32 frames, which enables recording of the dynamics of the process (shooting of movies) with intervals of 250 ns to 2 μs. Flows of nano- and microparticles from free surfaces of various materials (copper and tin) have been examined. Microparticle flows were emitted from grooves of 50-200 μs in size and joints (gaps) between metal parts. With the soft x-ray spectrum of SR one can explore the dynamics of a single microjet of micron size. The dynamics of density distribution along micro jets were determined. Under a shock wave (∼ 60 GPa) acting on tin disks, flows of microparticles from a smooth surface were recorded.

This work suggests and realizes a new method applying synchrotron radiation for remote measurement of density distribution at the front of a detonation wave. X-radiation was registered by a one-dimension gas detector DIMEX with a resolution of 100μm. The experimental setup is described. The methods for density reconstruction by measured intensity of transmitted radiation are also presented.

A one-coordinate gaseous detector of soft X-ray photons for wide-angle X-ray scattering (WAXS) studies is being developed. The detector operates in counting mode and is based on multi-stage Gas Electron Multiplier(GEM). Full size detector is assembled and has 67 degrees aperture with 350mm distance to the source, readout multi-strip structure with 2048 strips at 0.2mm pitch and is partially equipped with readout electronics in the central part. Main parameters of the detector have been measured with 8keV X-ray beam at VEPP-3 synchrotron ring. Spatial resolution of 470 um (FWHM) has been demonstrated that will allow to distinguish diffraction spots at 0.1 degrees.

The status of the experiment on the precise τ lepton mass measurement running at the VEPP-4M collider with the KEDR detector is reported. The mass value is evaluated from the τ+τ− cross section behavior around the production threshold. The preliminary result based on 15.2 pb−1 of data is mτ=1776.69−0.19+0.17±0.15 MeV.

The article describes a one-coordinate detector for diffraction experiments on a synchrotron radiation beam. The detector is being developed at the Budker Institute of Nuclear Physics SB RAS. Until recently the Institute was developing gas one-coordinate detectors, in particular a one-coordinate detector with calculated channels OD-3M, based on the technology of multi-wire proportional cameras. To provide a spatial resolution of better than 100 microns at photon energy in a wide energy range (3–30 keV), it is necessary to use solid-state microstrip or matrix sensors in combination with specialized integrated registration circuits. The developed SOCOD detector, using a microstrip sensor based on gallium arsenide as a recording element, operates in the mode of direct counting of photons with an energy of more than 3–4 keV and a speed of up to 1 MHz/channel. The article gives a general description of the current version of the detector, the block diagram of the recording channel, the software that allows users to control the operation of the detector and display the results obtained, and the developed algorithm for leveling the trigger thresholds in the channels. The results of electronic tests, the work of the alignment algorithm and their discussion are presented.

Present status of the development of the prototype of the Detector for imaging of explosions (DIMEX) based on silicon microtrip sensor is discussed. The prototype includes silicon p-in-n sensor with metal strips in direct contact with p-implants. Strips are 30 mm long and have 50 um pitch. Signals from the strips are read out with specially developed ASICs DMXS6A, that include 6 channels with DC compensation circuit at the input, four integrators, 32 analogue memory cells and output analogue shift register. The prototype detector has 96 registration channels provided with 16 DMXS6A ASICs. Each strip of the sensor is connected to the guard-ring through a 400 Ohm resistor and through 100 kOhm resistor to the input of the front-end ASIC. This resistive divider allows to adapt the dynamic range of the integrator of the ASIC to the full flux range of the beam line 8 at the VEPP-4M storage ring that includes 9-pole wiggler with 1.9 T B-field as SR source. The measurements of the dynamic range of the DIMEX-Si prototype demonstrate that maximum photon flux from one bunch that can be measured by this detector exceeds 100 000 photons per channel. For these measurements the sensor was inclined at an angle of 1.7 degrees with respect to the beam plane in order to increase quantum efficiency. The possibility to work in multi-bunch mode with bunches following in 55 ns is demonstrated, that proves that this detector can be successfully exploited at new SR-source SKIF that is under construction in Novosibirsk region.

Mixed formulations of ultrafine PETN+soda and RDX+soda have low detonation velocity and small critical diameters, which makes them attractive for application to new technological processes, such as welding explosion [1]. The above properties of these formulations are due to the use of nanopowders of PETN and RDX along with a phlegmatizing agent of sodium bicarbonate. The detonation parameters of these mixtures were studied using synchrotron radiation from the VEPP-3 accelerator (Budker Institute of Nuclear Physics). Techniques we developed were applied to the measurement of density distribution in the detonation front and the width of the reaction zone, as well as volume distribution of pressure, density and spread velocities in detonation of cylindrical charges.

The product of the electronic width of the ψ(2S) meson and the branching fraction of its decay to the muon pair was measured in the e+e−→ψ(2S)→μ+μ− 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:Γee×Bμμ=19.3±0.3±0.5eV. Adding the previous KEDR results on hadronic and leptonic channels, the values of the ψ(2S) electronic width were obtained under two assumptions: either with the assumption of lepton universalityΓee=2.279±0.015±0.042keV or without it, summing up hadronic and three independent leptonic channelsΓee=2.282±0.015±0.042keV.

This paper describes measurements of mass distribution along a microparticle jet with the use of synchrotron radiation (SR) from the VEPP-3 collider. The SR "soft" spectrum made it possible to measure microparticle jets of a record (minimum) density of about 1 mg/cm3. Simultaneous recording of microparticle jets using piezoelectric sensors made it possible to compare and mutually complement their readings.

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

Since 2004 the KEDR detector at the VEPP-4M collider has taken several data sets in the ψ(2S) region, acquiring total luminosity of about 7 pb -1 , which corresponds to more than 3.5 × 10 6 ψ(2S). We report the preliminary value of Γ ee × Γ μμ /Γ = 19.4 ± 0.4 ± 1.1 eV for ψ(2S).

We report results of experiments performed with the KEDR detector at the VEPP-4M e + e - collider. They include final results for the mass and other parameters of the J/ψ, ψ(2S) and ψ(3770) and J/ψ → γη c branching fraction determination.

The KEDR collaboration has taken data for R measurements at energies 3.1–3.7 GeV. Preliminary results from the analysis of these data are presented.

Recent results from the KEDR detector obtained in the charmonium energy range are reported: high-precision measurement of the J/ψ and ψ(2S) masses, study of their leptonic decays and J/ψ → η c γ decay

We describe recent results from the KEDR detector at the VEPP-4Mcollider. They include: a search for narrow resonances between 1.85 and 3.1 GeV, a test of leptonic universality by comparing partial widths of the J/ψ resonance into electron and muon pairs, a determination of the main parameters of the ψ(2S) and a measurement of ψ(3770) parameters.

We report a study of the decays B -> D_s1(2536)+ anti-D(*), where anti-D(*) is anti-D0, D- or D*-, using a sample of 657 x 10^6 B anti-B pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. The branching fractions of the decays B+ -> D_s1(2536)+ anti-D0, B0 -> D_s1(2536)+ D- and B0 -> D_s1(2536)+ D*- multiplied by that of D_s1(2536)+ -> (D*0K+ + D*+K0) are found to be (3.97+-0.85+-0.56) x 10^-4, (2.75+-0.62+-0.36) x 10^-4 and (5.01+-1.21+-0.70) x 10^-4, respectively.

The interference fragmentation function translates the fragmentation of a quark with a transverse projection of the spin into an azimuthal asymmetry of two final-state hadrons. In e+e- annihilation the product of two interference fragmentation functions is measured. We report nonzero asymmetries for pairs of charge-ordered pi+pi- pairs, which indicate a significant interference fragmentation function in this channel. The results are obtained from a 672 fb-1 data sample that contains 711 \times 106 pi+pi- pairs and was collected at and near the ?(4S) resonance, with the Belle detector at the KEKB asymmetric-energy e+e- collider.

We report a new precise determination of the leptonic widths of the J/psi meson performed with the KEDR detector at the VEPP-4M $e^{+}e^{-}$ collider. The measured values of the J/psi parameters are: \Gamma_{ee}\times\Gamma_{ee}/\Gamma = 0.3323 \pm 0.0064 (stat.) \pm 0.0048 (syst.) keV \Gamma_{ee}\times\Gamma_{\mu\mu}/\Gamma=0.3318 \pm 0.0052 (stat.) \pm 0.0063 (syst.) keV. Assuming $e\mu$ universality and using the table value of the branching ratios the leptonic \Gamma_{ll}= 5.59 \pm 0.12 keV width and the total \Gamma=94.1 \pm 2.7 keV widths were obtained. We also discuss in detail a method to calculate radiative corrections at a narrow resonance.

We report a new precise determination of the leptonic widths of the J/psi meson performed with the KEDR detector at the VEPP-4M $e^{+}e^{-}$ collider. The measured values of the J/psi parameters are: Γ_{ee}\timesΓ_{ee}/Γ= 0.3323 \pm 0.0064 (stat.) \pm 0.0048 (syst.) keV Γ_{ee}\timesΓ_{μμ}/Γ=0.3318 \pm 0.0052 (stat.) \pm 0.0063 (syst.) keV. Assuming $eμ$ universality and using the table value of the branching ratios the leptonic Γ_{ll}= 5.59 \pm 0.12 keV width and the total Γ=94.1 \pm 2.7 keV widths were obtained. We also discuss in detail a method to calculate radiative corrections at a narrow resonance.

Abstract The products of the electron width of the J / ψ meson and the branching fraction of its decays to the lepton pairs were measured using data from the KEDR experiment at the VEPP-4M electron–positron collider. The results are Γ e e × Γ e e / Γ = 0.3323 ± 0.0064 ( stat. ) ± 0.0048 ( syst. ) keV , Γ e e × Γ μ μ / Γ = 0.3318 ± 0.0052 ( stat. ) ± 0.0063 ( syst. ) keV . Their combinations Γ e e × ( Γ e e + Γ μ μ ) / Γ = 0.6641 ± 0.0082 ( stat. ) ± 0.0100 ( syst. ) keV , Γ e e / Γ μ μ = 1.002 ± 0.021 ( stat. ) ± 0.013 ( syst. ) can be used to improve the accuracy of the leptonic and full widths and test leptonic universality. Assuming eμ universality and using the world average value of the lepton branching fraction, we also determine the leptonic Γ l l = 5.59 ± 0.12 keV and total Γ = 94.1 ± 2.7 keV widths of the J / ψ meson.

The products of the electron width of the J/ψ meson and the branching fraction of its decays to the lepton pairs were measured using data from the KEDR experiment at the VEPP-4M electron–positron collider. The results are Γee×Γee/Γ=0.3323±0.0064(stat.)±0.0048(syst.) keV, Γee×Γμμ/Γ=0.3318±0.0052(stat.)±0.0063(syst.) keV. Their combinations Γee×(Γee+Γμμ)/Γ=0.6641±0.0082(stat.)±0.0100(syst.) keV, Γee/Γμμ=1.002±0.021(stat.)±0.013(syst.) can be used to improve the accuracy of the leptonic and full widths and test leptonic universality.

We have searched for the Cabibbo-suppressed decay $\Lambda_c^+\to\phi p\pi^0$ in $e^+e^-$ collisions using a data sample corresponding to an integrated luminosity of 915 $\rm fb^{-1}$. The data were collected by the Belle experiment at the KEKB $e^+e^-$ asymmetric-energy collider running at or near the $\Upsilon(4S)$ and $\Upsilon(5S)$ resonances. No significant signal is observed, and we set an upper limit on the branching fraction of $\mathcal{B}(\Lambda_c^+\to \phi p\pi^0) <15.3\times10^{-5}$ at 90% confidence level. The contribution for nonresonant $\Lambda_c^+\to K^+K^- p\pi^0$ decays is found to be consistent with zero and the corresponding upper limit on its branching fraction is set to be $\mathcal{B}(\Lambda_c^+\to K^+K^-p\pi^0)_{\rm NR} <6.3\times10^{-5} $ at 90% confidence level. We also measure the branching fraction for the Cabibbo-favored decay $\Lambda_c^+\to K^-\pi^+p\pi^0$; the result is $\mathcal{B}(\Lambda_c^+\to K^-\pi^+p\pi^0)= (4.42\pm0.05\, (\rm stat.) \pm 0.12\, (\rm syst.) \pm 0.16\, (\mathcal{B}_{\rm Norm}))\%$, which is the most precise measurement to date. Finally, we have searched for an intermediate hidden-strangeness pentaquark decay $P^+_s\to\phi p$. We see no evidence for this intermediate decay and set an upper limit on the product branching fraction of ${\cal B}(\Lambda_c^+\to P^+_s \pi^0)\times {\cal B}(P^+_s\to\phi p) <8.3\times 10^{-5}$ at 90% confidence level.