Search

Detection of antineutrino by the reaction of the inverse β-decay can be used for an independent monitoring of a nuclear reactor power. DANSS detector is located directly under a commercial WWER-1000 reactor and counts up to 5000 antineutrino per day, providing the accuracy of 1.5% in 2 days of the flux measurement. A powerful system of the passive and active shielding in combination with the fine spatial segmentation of the detector allows to diminish the contribution of the background processes to a level, negligible in comparison to the statistical error. The influence of the nuclear fuel composition on the neutrino flux can be accounted for based on the input from the NPP staff.

The detection equipment of the DANSS setup includes 2500 silicon photomultipliers and approximately 100 photomultiplier tubes (PMTs). The system of data acquisition from these photosensors is based on waveform digitization, with which it is possible to simultaneously obtain both amplitude and timing information. The modules of waveform digitizers (WFDs) are made to the VME standard and allow parallel digitization of 64 differential signals at a frequency of 125 MHz with a 12-bit amplitude resolution. The programmable logic of the WFDs provides production of the system trigger based on the analysis of the PMT signals and its propagation without any additional hardware. Owing to the extremely low analog noise, it is possible to use the full dynamic range of the digitization. These WFD modules are superior to other similar modules in the throughput and may find wide application to perform similar tasks of waveform digitization.

The transverse nonuniformity of the light yield in scintillator strips of the DANSS detector was investigated on a test setup that was specially designed for this purpose using proportional chambers with a wire pitch of 1 mm. It is shown that using the approaches that were used in the DANSS experiment, the variation in the light yield due to the geometric features of the strip design is approximately 8% for a minimum ionizing particle. This study can be useful for making estimates and designing similar detectors.

DANSS is a highly segmented 1~m${}^3$ plastic scintillator detector. Its 2500 one meter long scintillator strips have a Gd-loaded reflective cover. The DANSS detector is placed under an industrial 3.1~$\mathrm{GW_{th}}$ reactor of the Kalinin Nuclear Power Plant 350~km NW from Moscow. The distance to the core is varied on-line from 10.7~m to 12.7~m. The reactor building provides about 50~m water-equivalent shielding against the cosmic background. DANSS detects almost 5000 $\widetilde\nu_e$ per day at the closest position with the cosmic background less than 3$\%$. The inverse beta decay process is used to detect $\widetilde\nu_e$. Sterile neutrinos are searched for assuming the $4\nu$ model (3 active and 1 sterile $\nu$). The exclusion area in the $\Delta m_{14}^2,\sin^22\theta_{14}$ plane is obtained using a ratio of positron energy spectra collected at different distances. Therefore results do not depend on the shape and normalization of the reactor $\widetilde\nu_e$ spectrum, as well as on the detector efficiency. Results are based on 966 thousand antineutrino events collected at 3 distances from the reactor core. The excluded area covers a wide range of the sterile neutrino parameters up to $\sin^22\theta_{14}, Comment: 10 pages, 13 figures, version accepted for publication

The analysis of high-precision ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}p$ cross-sectional data from the EPECUR Collaboration based on the multichannel $K$-matrix approach is presented. The sharp structures seen in these data are studied in terms of both opening thresholds and new resonance contributions. Some prominent features are found to be due to the opening $K\mathrm{\ensuremath{\Sigma}}$ channel. However, a complete description of the data is improved with the addition of two narrow resonant structures at $W\ensuremath{\sim}1.686$ and $W\ensuremath{\sim}1.720\phantom{\rule{4.pt}{0ex}}\mathrm{GeV}$. These structures are interpreted as manifestations of ${S}_{11}$ and ${P}_{11}$ resonances. The underlying nature of the observed phenomena is discussed.

Ceramic samples of copper oxide were synthesized and their microstructure, elemental composition and electrical properties were investigated before and after the influence of YAG : Nd laser radiation. It was discovered that laser radiation leads to the fusion of granules and to a decrease in oxygen concentration in the surface layer of the sample. After the laser treatment the electrical properties of the samples pre-coated and not coated with copper film differ significantly, in particular the resistive thermal activation energy of these samples differs several times. For all the samples the current–voltage characteristics were linear at small values of the current.

A new method for fabricating large-area thin films of uniform thickness on a rotating substrate is proposed. Its distinctive features are (i) the presence of a diaphragm, partially transmitting the evaporated material, between the target and substrate and (ii) the translatory motion of the rotating substrate with respect to the target at a certain velocity. The method proposed makes it possible to obtain thin films of uniform thickness on substrates with sizes limited by only the deposition chamber size. The method is experimentally verified by depositing thin CuO films on silicon substrates placed over the radius of a disk 300 mm in diameter. The deviation of the film thickness from the average value does not exceed {+-}3% throughout the entire radius, which confirms good prospects of this method for microelectronics, optical industry, and other modern technologies. (laser technology)

Measurements of reactor antineutrino play an important role in the efforts at the frontier of the modern physics. The DANSS collaboration presents preliminary results of a one year run with a cubic meter solid state detector placed below 3.1 GW industrial light water reactor. The experiment is sensitive to sterile neutrino in the most interesting region of mixing parameter space. 2500 scintillation strips of the sensitive volume of the detector have multilayer passive shielding of copper, lead and borated polyethylene and active muon veto. Detector position below the reactor gives an advantage of overburden about 50 m of water equivalent providing factor of six in cosmic muon suppression and eliminating fast neutrons.The detector is placed on a vertically movable platform which allows to change the distance to the reactor core center in the range 10.7-12.7 m within a few minutes. The strips are read out individually by SiPMs and in groups of 50 by PMTs. 5000 inverse beta-decay events per day are collected in the fiducial volume, which is 78% of the whole detector, at the position closest to the reactor. Overburden, active veto and good segmentation of the detector result in an excellent signal to background ratio. The talk is dedicated to the data analysis and preliminary results. The experiment status is also presented.

A program of measurement of the polarization parameter P in elastic {pi}{sup +}p interaction in the resonance region of backward pion scattering is presented. This program is aimed at determining the bifurcation points of the trajectory of zeros of the pion-nucleon amplitude and, hence, at unambiguously reconstructing the amplitude of {pi}N scattering in the second resonance region. It is planned to perform a relevant experiment in a pion beam from the accelerator of the Institute of Experimental and Theoretical Physics (ITEP, Moscow)

The SPIN-P experimental setup was designed for measuring the P asymmetry during pion scattering into the backward hemisphere at a minimum differential cross section of elastic πpscattering. The physical grounds of the experiment and the results of its simulation by the Monte Carlo method are presented. The setup is composed of a polarized proton target in a superconducting solenoid with vertical polarization of free protons, wire track detectors, scintillation counters, electronics for data readout and processing, and an appropriate computer network. The experimental program has been under way since 2002 on the pion beam of the proton synchrotron at the Institute of Theoretical and Experimental Physics (Moscow).

Experimental data on the spin-rotation parameters A and R in elasticπ+p interaction were obtained for the first time at a momentum of pπ = 1.62 GeV/c. These data are necessary for unambiguously reconstructing the amplitude of pion-nucleon scattering and, hence, for deducing a correct spectrum of nonstrange baryon resonances. In order to obtain results for the polarization parameters A and R with the minimum possible systematic error, the carbon polarimeter used was preliminarily calibrated in a dedicated experiment; that is, the analyzing power was measured in proton-carbon scattering for incidentproton energies in the range Tp=0.7–1.3 GeV. The experimental data reported in the present article were obtained by a collaboration of researchers from the Petersburg Nuclear Physics Institute and Institute of Theoretical and Experimental Physics (ITEP, Moscow) at the ITEP synchrotron.

The coefficients of two-photon absorption of 30- and 70-ns ArF laser pulses in high-purity CaF2, BaF2, and Al2O3 crystals are measured by the method of nonlinear transmission to be 2.2 ± 0.8, 2.3 ± 0.8, and 5.6 ± 2.2 cm GW-1, respectively. The thresholds of the laser breakdown of the surface of crystals are determined.

The spin rotation parameters A and R were measured for the elastic pion-proton scattering by the PNPI-ITEP collaboration in the D13 (1700), ΔS31(1900), ΔP33(1920) and ΔD33 (1940) resonances region. These resonances were absent in the set of partial wave analysis (PWA) of the Virginia Polytechnic Institute group (VPI), but was included in the tables of the Review of Particle Physics. The main goal of the experimental program was to resolve the current PWA’s disagreement in spin rotation parameters value predictions. Simultaneously with A and R the polarization parameter P was measured with the purpose to improve the experimental data base and estimate the experimental systematic errors. Our results for spin rotation parameters A and |R| are in agreement with PWA VPI predictions.

New experimental data on the spin-rotation parameters A and R measured for elastic π ± p scattering in the resonance region and on the asymmetry in pC scattering at primary momenta in the range 1.35–2.02 GeV/c, as well as in quasielastic proton scattering on nuclei in the same momentum range, are summarized. All these data were recently obtained by using the proton synchrotron installed at the Institute of Theoretical and Experimental Physics (ITEP, Moscow). The spectrum and features of seven isospin-3/2 baryon resonances that form a peak in the total cross section at a c.m. energy of 1.9 GeV are analyzed on the basis of new data on the parameters A and R, and the results of this analysis are presented. The experiments surveyed in this article were performed by a collaboration of researchers from ITEP and the Petersburg Nuclear Physics Institute (PNPI, Gatchina), the ITEP-PNPI collaboration.

The spin rotation parameters A and R were measured for the elastic pion-proton scattering by the PNPI-ITEP collaboration in the D13(1700) resonance region. The main goal of the experimental program is to resolve the current partial-wave analyses (PWA) uncertainties. Simultaneously with A and R the polarization parameter P was measured with the purpose to improve the experimental database and estimate systematic errors. The constraint which demands a smooth energy dependence of all π-p transverse amplitude zeros in the complex plane together with the new experimental data on A parameter can lead to the conclusion that the Barrelet branch of “zero trajectories" is chosen improperly in PWA of the Carnegie-Mellon-Lawrence-Berkely-Laboratory groups at the range of the pion beam momentum near 1.0 GeV/c. The setup included a longitudinally polarized proton target with superconductive magnet, multiwire spark chambers and carbon polarimeter with thick filter. The experiment was performed at the ITEP proton synchrotron, Moscow.

Lasing on HF upon optical pumping by emission of an open discharge, using NF3 and ClF5 as donors of fluorine atoms, was obtained for the first time in a chemical laser and the bleaching-wave mode was realised in a chemical HF laser. An open surface discharge was used as a pump source. The velocity of the bleaching wave, which was formed under its action, reached ~8 km s-1. The formation of this wave leads to a rapid (with an ultrasonic velocity) replacement of the working medium in the lasing region, which provides a quantum laser efficiency close to unity. The optimum compo-sition of the working mixture was found to be NF3:H2:Kr =6:10:125 Torr. For this composition, the output laser energy in a 3.2-μs pulse reached ~0.4 J and the specific output energy was 3.5 J litre-1. Approximately the same output characteristics of laser emission (0.35 J in a 3.5-μs pulse in the ClF5:H2:Kr=3:20:50 Torr mixture) were obtained in the system using ClF5 as donors of fluorine atoms.

The paper presents the experimental results on measurements of carbon analyzing power for polarized protons at momenta 1.36, 1.60, 1.78, 2.02 GeV/c and the carbon thickness 4.9, 19.4, 36.5 g/cm2. The data shows that the analyzing power does not depend on the thickness in the interval 19–36 g/cm2. The results of this experiment for carbon thickness 19.4 and 36.5 g/cm2 together with the Saclay data were used for parametrization over the momentum and the scattering angle. Proton polarization in the quasielastic scattering on carbon at 10.5° was also measured. The experiment was completed at the ITEP accelerator.

The ITEP-PNPI collaboration presents first results of the spin rotation parameter A+ measurements in the second resonance region. The experiment was performed on ITEP accelerator at positive pion beam momentum 1·43 GeV/c (√s= 1·90 GeV/c) for scattering angles 0cm = 127° and 133°. Main parts of the setup were a polarized proton target and a carbon-plate polarimeter. The results of measurements are in agreement with the predictions of the partial-wave analysis VPI and in contradiction with the predictions of PWA's KH and CMB.

The DANSS project is aimed at creating a relatively compact neutrino spectrometer which does not contain any flammable or other dangerous liquids and may therefore be located very close to the core of an industrial power reactor. As a result, it is expected that high neutrino flux would provide about 15,000 IBD interactions per day in the detector with a sensitive volume of 1 m3. High segmentation of the plastic scintillator will allow to suppress a background down to a ~1% level. Numerous tests performed with a simplified pilot prototype DANSSino under a 3 GWth reactor of the Kalinin NPP have demonstrated operability of the chosen design. The DANSS detector surrounded with a composite shield is movable by means of a special lifting gear, varying the distance to the reactor core in a range from 10 m to 12 m. Due to this feature, it could be used not only for the reactor monitoring, but also for fundamental research including short-range neutrino oscillations to the sterile state. Supposing one-year measurement, the sensitivity to the oscillation parameters is expected to reach a level of sin2(2θnew) ~ 5 × 10−3 with Δ m2 ⊂ (0.02–5.0) eV2.

The ITEP-PNPI collaboration presents the first results of the spin rotation parameter A+ measurements in the second resonance region. The experiment was performed at the ITEP accelerator at a positive pion beam momentum 1.43 GeV/c for scattering angles θcm = 127° and 133°. The setup was based on a polarized proton target and a carbon-plate polarimeter. The obtained data is compared with the predictions of the existing partial-wave analyses.

A UV-preionized XeCI laser with active-region cross section 4 × 4 cm is investigated. We show that the use of a laser excitation system based on KMK and IK-100 capacitors makes possible a lasing pulse of 500 nsec (FWHM). The duration of the lasing pulse is found to be influenced by the components making up the working gas mixture.

Results of systematic measurements of the asymmetry parameter in the elastic scattering of pions on polarized protons at 1.4–2.1 GeV/ c in the backward hemisphere are presented together with a test of the isospin invariance of the data set available on pion-proton scattering in the investigated momentum range. The transversity isodoublet amplitudes at 1.98 and 2.07 GeV/ c are reconstructed. The obtained data, the isospin analysis and amplitude reconstruction results are compared with the current phase-shift analysis predictions.

The main goal of this proposal is the search for a narrow cryptoexotic nucleon resonance by scanning of the pi- p system invariant mass in the region (1610-1770) MeV with the detection of pi- p and K Lambda decays. The scan is supposed to be done by the variation of the incident pi- momentum and its measurement with the accuracy of up to +-0.1% (better than 1 MeV in terms of the invariant mass in the whole energy range) with a set of proportional chambers located in the first focus of the magnetooptical channel. High sensitivity of the method to the resonance under search is shown. The secondary particles scattered from a liquid hydrogen target are detected by sets of the wire drift chambers equipped with modern electronics. The time scale of the project is about 3 years. The budget estimate including manpower, the apparatus and operation cost, is about 40 million rubles. The beam time required is (4-6) two week runs on "high" (10 GeV/c) flattop of the ITEP proton synchrotron.

The existing models of baryons usually predict considerably more resonance (three or more in number) than it was found by investigation of elastic pion‐nucleon scattering. This disagreement invites further investigation of the pion‐nucleon interaction and among other things the measurement of spin rotation parameters A and R in the elastic pion‐nucleon scattering.Recent experiments of the PNPI and PNPI‐ITEP collaborations resolved a part of twofold ambiguities of the existing partial wave analyses (PWA). These results were used in the last PWA of the George Washington University group SP06. The proposal for the additional spin rotation parameters A and R measurement in the resonance region is motivated. Such additional measurements are necessary to resolve remaining twofold ambiguities of the existing PWAs.

The asymmetry parameter P was measured for the elastic pion-proton scattering in the very backward angular region of theta_cm ~ 150-170^o at several pion beam energies in the invariant mass range containing most of the pion-proton resonances. The general goal of the experimental program was to provide new data for partial wave analyses in order to resolve their uncertainties in the baryon resonance region to allow the unambiguous baryon spectrum reconstructions. Until recently the parameter P was not measured in the examined domain that might be explained by the extremely low cross section. At the same time the predictions of various partial wave analyses are far from agreement in some kinematic areas and specifically those areas were chosen for the measurements where the disagreement is most pronouncing. The experiment was performed at the ITEP U-10 proton synchrotron, Moscow, by the ITEP-PNPI collaboration in the latest 5 years., Comment: 6 pages, 5 figures. to be submitted to the European Physical Journal

6-Aminouracils and N-substituted derivatives are cyanoacetylated to give 5-cyanoacetyl-6-aminouracils. In the presence of bases these are converted to pyrido[2,3-d]pyrimidine-2,4,5-triones in high yields.

Latest results by the ITEP‐PNPI collaboration on the asymmetry in the π+p elastic scattering are presented. The data were obtained for the first time in the region of backward angles with low cross section, where the predictions of the partial wave analyses are not reliable. The results at 1.94 GeV/c are in favor of the older KH80 analysis and show noticeable deviation from the latest FA06 solution by GWU group. At 2.07 GeV/c very low cross section did not allow to achieve good accuracy. Yet the data do not follow any of the PWA predictions and definitely disagree with SP06 analysis.

The idea of ‘EPECUR’ was inspired by the recent splash of the activity around the pentaquark matters. The goal of the experiment is the search for narrow resonant states in the reactions π−p → π−p and π−p → K0Λ based on the very precise cross section measurements in fine energy steps of 0.5 MeV in terms of the invariant mass. As a valuable byproduct of the second stage of the experiment, Λ‐polarization in π−p → K0Λ can be measured, based on the well‐known weak Λ‐decay asymmetry. The expected statistical significance of the measurement overrides the best existing data from ‘NIMROD’ detector by an order of magnitude. The experimental setup is under construction at the ITEP proton synchrotron in collaboration with PNPI and ACU.

The ITEP-PNPI collaboration presents new results of the measurements of the spin rotation parameter A in the elastic scattering of negative pions on protons at P_beam=1.43 GeV/c. The results are compared to the predictions of several partial wave analyses. The experiment was performed at the ITEP proton synchrotron, Moscow., 4 pages, 5 figures

The paper presents new experimental data on the spin rotation parameter A obtained recently by ITEP‐PNPI collaboration at the ITEP accelerator. The set of measurements was performed in carefully chosen critical points with precision sufficient for choosing the correct branches of partial wave analyses. The data for both π+ and π−‐scattering at 1.0, 1.43 and 1.62 GeV/c is included.

One of the main sources of the information about nuclear resonances are partial wave analyses (PWA) of pion-proton elastic scattering. Nearly all of the data available for PWA were obtained more than 20 years ago with old measurement techniques. The talk presents new high precision data obtained recently by the EPECUR collaboration. The experiment features high statistics and better than 1 MeV resolution in the invariant mass thus allowing searches for narrow resonances with the coupling to the πp channel as low as 5%. The experimental setup consists of a 25 cm long liquid hydrogen target in a non-magnetic spectrometer of wire drift chambers with hexagonal structure. The measurements started in 2009. 3 billions of triggers are already collected with positive and negative pion beams in the beam momentum range 820-1330 MeV/c.

The EPECUR collaboration presents new high precision data on the pion- proton elastic scattering in the second resonance region. The experiment EPECUR is placed on the universal beam channel of the accelerator ITEP. The setup features 0.1% beam pion momentum tagging system, 25 cm long liquid hydrogen target, placed in my- lar container and beryllium outer shell, low material wire drift chambers and high perfor- mance DAQ. More than 3 billions of triggers have been collected. The data cover pion beam momentum range 0.8 - 1.3 GeV/c and 40-120 degrees center-of-mass scattering angle range for both positive and negative pions. The measured differential cross section has 2% statistical accuracy in 2 degrees angle and 5 MeV/c momentum intervals.

The ITEP-PNPI collaboration presents the results of the measurements of the spin rotation parameter A in the elastic scattering of positive and negative pions on protons at P_beam = 1.62 GeV/c. The setup included a longitudinally-polarized proton target with superconductive magnet, multiwire spark chambers and a carbon polarimeter with thick filter. Results are compared to the predictions of partial wave analyses. The experiment was performed at the ITEP proton synchrotron, Moscow., 7 pages, 3 figures. To be published in Phys. Lett. B

The behavior of the dielectric permittivity of a mixture of disperse materials is investigated for a change in the volume content of the component with a high value of the dielectric permittivity. An analysis is performed from the viewpoint of computing the dielectric permittivity of such mixtures. A formula is proposed for computation of the dielectric permittivity of mixtures of disperse materials with water.

A simple method was develeped for the synthesis of n1- and N3-alkyl- and N1,N3-dialkyl(aryl, alkyl)-5-chloroacetyl-6-aminouracil by reaction of 6-aminouracils with chloroacetyl chloride in monochloroacetic acid. 2,4,5-Trioxopyrrole[2,3-d]pyrimidines were obtained by the action of aqueous alkali on N1alkyl-5-chloroacetyl-6-aminouracils and by the action of sodium ethoxide on N3-alkyl- and N1,N3-dialkyl(aryl, alkyl)-5-chloroacetyl-6-aminouracils. When there is an alkyl substituent attached to the 3-N atom in 2,4,5-trioxopyrrolo[2,3-d]pyrimidines, the pyrrole ring readily opens up under the influence of alkali to give 5-hydroxyacetyl-6-amino uracils.

The behavior of the dielectric permittivity of a mixture of disperse materials with change in volume content of the component with high dielectric permittivity (water) and temperature is investigated. An analysis of the results is presented. A formula is given for the calculation of the dielectric permittivity of moist disperse materials as a function of the temperature.

In the paper an analysis is presented of the dependence of the position of the low-frequency dispersion region of a semiconducting heterogeneous specimen-spacers system on the volume concentration of the conducting component, the thickness of the specimen, the thickness (capacity) of the spacers. It is concluded that there exists a surface capacity due to regions of the nonconducting phase of the specimen confined between the spacers and a conducting infinite cluster.

An analysis is made of the existing waveguide methods (short-circuit, “infinite” layer, variable reactive load, “direct” determination of the wavelength and pattern of the electromagnetic field in the investigated material) as applied to disperse materials characterized by high losses. A comparison of the short-circuit method with the direct measurement of the propagation constant is used to show that the latter is preferable when applied to materials with large values of the permittivity (in excess of 10) and a large loss-angle tangent (in excess of 0.1). This method does not require complex mathematical calculations and makes it possible to determine unambiguously the permittivity, whereas the values of the loss-angle tangent are physically more reasonable.

2,4-Dioxo-1,2,3,4-tetrahydropyrido [2,3-d]pyrimidines, the structures of which were proved by the PMR and the IR spectra, are formed in the condensation of mono- and di-N-alkyl-5-formyl-6-aminouracils with cyanoacetic acid and its esters, acetoacetic ester, and malonic acid dinitrile.

The dependence of the electrical conductivity of a mixture of finely disperse graphite with quartz sand and moist quartz sand on the composition is investigated. It is shown that, in the region of critical and near-critical concentrations of the conducting component, the dependence is satisfactorily described by two power-law equations of flow theory with two different threshold values of the conducting-phase concentration. In this concentration range, the conductivity of the sandgraphite system is satisfactorily modeled by a lattice bond problem. The electrical transfer in the sand-KCl solution system may be modeled by a lattice point problem in the representation of the moist system as a mixture of dielectric particles coated with an electrolyte film (conducting particles) and dry dielectric particles (nonconducting particles).