V. Zhulanov

Observation of Transverse Polarization Asymmetries of Charged Pion Pairs in e+e- Annihilation near √[s]= 10.58 GeV

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 π(+)π(-) 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 × 10(6) π(+)π(-) pairs and was collected at and near the Υ(4S) resonance, with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider.

Operation of the triple-GEM detectors in the tagging system of the KEDR experiment on the VEPP-4M collider

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.

Measurement of main parameters of the ψ(2S) resonance

A high-precision determination of the main parameters of th eψ(2S ) resonance has been performed with the KEDR detector at the VEPP-4Me+e− collider in three scans of the ψ(2S )–ψ(3770) energy range. Fitting the energy dependence of the mu ltihadron cross section in the vicinity of theψ(2S ) we obtainedthe mass value M = 3686.114± 0.007± 0.011 +0.002 −0.012 MeV and the product of the electron partial width by the branchin g fraction into hadrons Γee × Bh = 2.233± 0.015± 0.037± 0.020 keV. The third error quoted is an estimate of the model dependence of the result due to assumptions on the interference e ffects 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 th e absolute branching fractions in many experiments. Usingthe result presented and the world average values of the electron and hadron branchin g 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 mor e precise than any of the previous experiments.

Measurement of ψ(3770) parameters

Abstract We report the final results of a study of the ψ ( 3770 ) meson using a data sample collected with the KEDR detector at the VEPP-4M electron–positron collider. The data analysis takes into account interference between the resonant and nonresonant D 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 N R ( s ) . Our results for the mass and total width of ψ ( 3770 ) are M = 3779.2 − 1.7 + 1.8 − 0.7 + 0.5 − 0.3 + 0.3 MeV , Γ = 24.9 − 4.0 + 4.6 − 0.6 + 0.5 − 0.9 + 0.2 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 ) Γ e e = 154 − 58 + 79 − 9 + 17 − 25 + 13 eV , ( 2 ) Γ e e = 414 − 80 + 72 − 26 + 24 − 10 + 90 eV . Our statistics are insufficient to prefer one solution to another. The Solution (2) mitigates the problem of non- D 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 cannot be directly compared with the corresponding PDG values obtained ignoring this effect.

Measurement of R uds and R between 3.12 and 3.72 GeV at the KEDR detector

Using the KEDR detector at the VEPP-4M e + e − e + e − collider, we have measured the values of R uds R 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% 3.3 % at most of energy points with a systematic uncertainty of about 2.1% 2.1 % . At the moment it is the most accurate measurement of R(s) R ( s ) in this energy range.

Application of introduced nano-diamonds for the study of carbon condensation during detonation of condensed explosives

This paper describes experimental studies of the formation of nano-diamonds during the 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 the 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.

Development of a one-dimensional detector for the study of explosions with a synchrotron radiation beam.

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.

Detector for imaging of explosions: present status and future prospects with higher energy X-rays.

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

Measurement of R between 1.84 and 3.05 GeV at the KEDR detector

Abstract 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 % .

GEM-based detectors for SR imaging and particle tracking

Status of several projects under development in Budker INP with GEM-based detec- tors for synchrotron radiation imaging and particle tracki ng 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.