Leonid Levchuk

We have measured the cross section for quasielastic $1p$-shell proton knockout in the ${}^{16}\mathrm{O}({e,e}^{\ensuremath{'}}p)$ reaction at $\ensuremath{\omega}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.439\mathrm{GeV}$ and ${Q}^{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.8(\mathrm{GeV}/c{)}^{2}$ for missing momentum ${P}_{\mathrm{miss}}\ensuremath{\le}355\mathrm{MeV}/c$. We have extracted the response functions ${R}_{L+TT}$, ${R}_{T}$, ${R}_{\mathrm{LT}}$, and the left-right asymmetry, ${A}_{\mathrm{LT}}$, for the ${1p}_{1/2}$ and the ${1p}_{3/2}$ states. The data are well described by relativistic distorted wave impulse approximation calculations. At large ${P}_{\mathrm{miss}}$, the structure observed in ${A}_{\mathrm{LT}}$ indicates the existence of dynamical relativistic effects.

Extensive measurements have been made with pions, electrons and muons on four production wedges of the compact muon solenoid (CMS) hadron barrel (HB) calorimeter in the H2 beam line at CERN with particle momenta varying from 20 to 300 GeV/c. The time structure of the events was measured with the full chain of preproduction front-end electronics running at 34 MHz. Moving-wire radioactive source data were also collected for all scintillator layers in the HB. The energy dependent time slewing effect was measured and tuned for optimal performance.

The first (→e,e′→p) polarization transfer measurements on a nucleus heavier than deuterium have been carried out at Jefferson Laboratory. Transverse and longitudinal components of the polarization of protons ejected in the reaction 16O(→e,e′→p) were measured in quasielastic perpendicular kinematics at a Q2 of 0.8 (GeV/c)2. The data are in good agreement with state of the art calculations.Received 7 January 2000DOI:https://doi.org/10.1103/PhysRevC.62.057302©2000 American Physical Society

The role of the motion of bound electrons in target atoms in electron beam polarization measurements by means of Möller scattering is discussed. It is shown that this effect can result in an essential overestimate of the asymmetry. This overestimate considerably exceeds the uncertainly of the target polarization, and, therefore, the effect should be taken into account in experiments with polarized electrons and in the development of Möller polarimeters. Some recommendations are given to eliminate this systematic error.

The physics program in Hall A at Jefferson Lab commenced in the summer of 1997 with a detailed investigation of the $^{16}\mathrm{O}(e,{e}^{\ensuremath{'}}p)$ reaction in quasielastic, constant $(q,\ensuremath{\omega})$ kinematics at ${Q}^{2}\ensuremath{\approx}0.8\phantom{\rule{0.3em}{0ex}}{(\mathrm{GeV}∕c)}^{2}$, $q\ensuremath{\approx}1\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}∕c$, and $\ensuremath{\omega}\ensuremath{\approx}445\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$. Use of a self-calibrating, self-normalizing, thin-film waterfall target enabled a systematically rigorous measurement. Five-fold differential cross-section data for the removal of protons from the $1p$-shell have been obtained for $0<{p}_{\mathrm{miss}}<350\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}∕c$. Six-fold differential cross-section data for $0<{E}_{\mathrm{miss}}<120\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ were obtained for $0<{p}_{\mathrm{miss}}<340\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}∕c$. These results have been used to extract the ${A}_{LT}$ asymmetry and the ${R}_{L}$, ${R}_{T}$, ${R}_{LT}$, and ${R}_{L+TT}$ effective response functions over a large range of ${E}_{\mathrm{miss}}$ and ${p}_{\mathrm{miss}}$. Detailed comparisons of the $1p$-shell data with Relativistic Distorted-Wave Impulse Approximation (RDWIA), Relativistic Optical-Model Eikonal Approximation (ROMEA), and Relativistic Multiple-Scattering Glauber Approximation (RMSGA) calculations indicate that two-body currents stemming from meson-exchange currents (MEC) and isobar currents (IC) are not needed to explain the data at this ${Q}^{2}$. Further, dynamical relativistic effects are strongly indicated by the observed structure in ${A}_{LT}$ at ${p}_{\mathrm{miss}}\ensuremath{\approx}300\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}∕c$. For $25<{E}_{\mathrm{miss}}<50\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ and ${p}_{\mathrm{miss}}\ensuremath{\approx}50\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}∕c$, proton knockout from the $1{s}_{1∕2}$-state dominates, and ROMEA calculations do an excellent job of explaining the data. However, as ${p}_{\mathrm{miss}}$ increases, the single-particle behavior of the reaction is increasingly hidden by more complicated processes, and for $280<{p}_{\mathrm{miss}}<340\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}∕c$, ROMEA calculations together with two-body currents stemming from MEC and IC account for the shape and transverse nature of the data, but only about half the magnitude of the measured cross section. For $50<{E}_{\mathrm{miss}}<120\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ and $145<{p}_{\mathrm{miss}}<340\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}∕c$, $(e,{e}^{\ensuremath{'}}pN)$ calculations which include the contributions of central and tensor correlations (two-nucleon correlations) together with MEC and IC (two-nucleon currents) account for only about half of the measured cross section. The kinematic consistency of the $1p$-shell normalization factors extracted from these data with respect to all available $^{16}\mathrm{O}(e,{e}^{\ensuremath{'}}p)$ data is also examined in detail. Finally, the ${Q}^{2}$-dependence of the normalization factors is discussed.

The effect of irradiation on the scintillation light output, optical transmittance, and luminescent spectra of composite scintillators based on grains of single crystals Gd2SiO5:Ce (GSO) and Gd2Si2O7:Ce (GPS) is studied. The dielectric gel Sylgard-184 is the base and the binder for the grains inside the composite scintillator. The paper presents and analyzes the results obtained for the scintillators exposed by 10 MeV electrons from the linear electron accelerator at room temperature. The exposure doses D≤250 Mrad. The dose rate is 0.2 or 1500 Mrad/h. The study has shown that the composite scintillators based on the grains of GSO and GPS are radiation-resistant over the range of the irradiation.

The effect of the annealing environment (vacuum, hydrogen) in the temperature range of 400 °C − 700 °C on the thermally activated ordering processes in the equiatomic FePd films is investigated. The absorption of hydrogen atoms affects the electronic structure and, therefore, the magnetic properties of the film. Ordering processes occur much faster under interaction with hydrogen than during annealing in a vacuum. It is shown that by changing the annealing parameters of the FePd film in a hydrogen atmosphere, it is possible to control the phase composition, reversibility of magnetic states: ferromagnetic ↔ paramagnetic. The application of the Raman spectroscopy allows identifying the dynamics of structural changes in the FePd films during the study of ordering processes.

The formalism that describes radiative-capture reactions at low energies within an extended two-cluster potential model is presented. Construction of the operator of single-photon emission is based on a generalisation of the Siegert theorem with which the amplitude of the electromagnetic process is constructed in an explicitly gauge-independent way. While the starting point for this construction is a microscopic (single-nucleon) current model, the resulting operator of low-energy photon emission by a two-cluster system is expressed in terms of macroscopic quantities for the clusters and does not depend directly on their intrinsic coordinates and momenta. The multichannel algebraic scattering (MCAS) approach has been used to construct the initial- and final-state wave functions. We present a general expression for the scattering wave function obtained from the MCAS T matrix taking into account inelastic channels and Coulomb distortion. The developed formalism has been tested on the He3(α,γ)Be7 reaction cross section at astrophysical energies. The energy dependence of the evaluated cross section and S factor agrees well with that extracted from measurement though the calculated quantities slightly overestimate data.

We report on the response of a prototype CMS hadron calorimeter module to charged particle beams of pions, muons, and electrons with momenta up to 375GeV/c. The data were taken at the H2 and H4 beamlines at CERN in 1995 and 1996. The prototype sampling calorimeter used copper absorber plates and scintillator tiles with wavelength shifting fibers for readout. The effects of a magnetic field of up to 3 T on the response of the calorimeter to muons, electrons, and pions are presented, and the effects of an upstream lead tungstate crystal electromagnetic calorimeter on the linearity and energy resolution of the combined calorimetric system to hadrons are evaluated. The results are compared with Monte Carlo simulations and are used to optimize the choice of total absorber depth, sampling frequency, and longitudinal readout segmentation.

The effect of irradiation on the scintillation light output, optical transmittance, and luminescent spectra of composite scintillators based on single crystal grains of Al2O3:Ti, is studied. The dielectric gel Sylgard-184 is the base and the binder for the grains inside the composite scintillator. The paper presents and analyses the results obtained for the scintillators exposed by 10 MeV electrons from the linear electron accelerator at room temperature. For exposure doses at least up to D∼550 Mrad when dose rate is 1500 Mrad/h and D∼125 Mrad when dose rate is 0.2 Mrad/h the composite scintillators are radiation-resistant.

We measured the cross section and response functions for the quasielastic 16O(e,e'p) reaction for missing energies 25< or =E(m)< or =120 MeV at missing momenta P(m)< or =340 MeV/c. For 25<E(m)<50 MeV and P(m) approximately 60 MeV/c, the reaction is dominated by a single 1s(1/2) proton knockout. At larger P(m), the single-particle aspects are increasingly masked by more complicated processes. Calculations which include pion exchange currents, isobar currents, and short-range correlations account for the shape and the transversity, but for only half of the magnitude of the measured cross section.

Plastic scintillators are often used as detectors in High Energy Physics (HEP), but have insufficient radiation hardness. Organization of better light collection inside a single detector may prolong operation life of scintillators. A finger-strip plastic scintillator option has many advantages to keep the excellent detector performance at high luminosity. Measurements assigned to show an advantage of a stripped detector vs. the un-stripped one in the range of increased absorbed doses and the smallest dose rates have been performed. This method has proved to be a good upgrade strategy.

Positive pion electroproduction from the deuteron near threshold has been considered within an approach based on the unitary transformation method. The gauge independence of the treatment is provided by using an explicitly gauge-independent expression for the reaction amplitude. The results of calculations for the kinematics of the experiments on forward-angle $\pi^ + $ meson electroproduction accomplished at Saclay and Jefferson Laboratory are discussed and compared with those given by the impulse approximation. It is shown that the observed behaviour of the cross-sections is in accordance with the calculations based on the pion-nucleon dynamics. In particular, the pion production rate suppression in the $^2{\rm H}({\rm e,e}'\pi^ + $ )nn reaction compared to that for the $^1{\rm H}({\rm e,e}'\pi^ + $ )n one can be due to such “nuclear medium” effects as nucleon motion and binding along with Pauli blocking in the final nn state.

In our previous works in this series, we investigated composite scintillators, i.e. scintillators based on a transparent gel composition containing single crystal grains of inorganic crystals (GSO:Ce, GPS:Ce, Al2O3:Ti, YSO:Ce and YAG:Ce). The gel composition was not only a binding material for scintillation grains. It was both a light-collecting medium in which a total scintillation signal from various grains was forming as well as a coating that protected scintillation grains from the effects of chemically active components of the atmosphere. At large cumulative doses of D, we observed a previously undescribed effect of scintillator cracking. In this work, as in previous works in this series, we irradiated composite scintillators on a linear electron accelerator. The electron energy was 10 MeV. We irradiated for a low (0.2 Mrad/h) and a high dose rate (1500 Mrad/h). At the low dose rate, cracking occurs at lower D values (about 100–200 Mrad) than under irradiation with the high dose rate (up to 500 Mrad). The luminescent characteristics of the scintillator changed insignificantly until the gel composition fixing single-crystal grains cracked. After the destruction of the gel composition, an abrupt deterioration in the properties of the sample was occurring. Additional studies have allowed us to show that nitrogen compounds, including nitric acid, can appear in the irradiation zone under the influence of radiation. The scintillator in the irradiation zone can either begin to expand under the influence of heating or (and) to crack when exposed to aggressive atmospheric components. There are two main hypotheses for describing the cracking of composite scintillators, requiring an analysis of the irradiation conditions, which this work is devoted. In this article, we conducted additional studies when the irradiated scintillators were in the atmosphere, or in a vacuum to compare and analyse the “temperature” and “radiation-chemical” hypothesis of composite scintillators cracking, as well as to confirm the conclusions of our analysis. The analysis we carried out in work proves that, at the low dose rate, nitrogen-containing compounds forming in the irradiation zone have a decisive influence on the effect of scintillator cracking. At the high dose rates, the main effect that leads to the cracking of scintillators is their heating, occurring under the influence of radiation.

The proton analyzing power Ay in pion production reaction pd --> pi0 3He has been calculated including one- and two-body meson production mechanisms with a proper treatment of the three-nucleon dynamics and an accurate solution of the 3N bound-state problem for phenomenological two-nucleon potentials. In the region around the Delta resonance, the structure of the analyzing power can be understood once interference effects among amplitudes describing intermediate Delta N formation in different orbital states are considered along with the additional interference with the S-wave pion production amplitudes. Then, the inclusion of three-nucleon dynamics in the initial state produces the structure of the analyzing power that has been observed experimentally.

To date, LuAG:Ce crystals are one of the most common scintillators, since they have been known for a long time and there are technologies for mass production of large-volume crystals. However, the scintillation properties of such crystals can be improved by creating mixed crystals with the replacement of some ions by others. In this work, composite scintillators based on the grown LuYAG:Ce inorganic crystals were produced. For the obtained samples, studies of optical transmission, luminescence, light output, and decay time were carried out. The optimal conditions and sizes of crystalline grains for the creation of composite scintillators have been determined.

Radiation resistance of composite scintillators containing grains of organic or inorganic single crystals has been analysed. The analysis is based on the study of composite scintillators containing grains Gd2SiO5:Ce (GSO:Ce), Gd2Si2O7:Ce (GPS:Ce), Al2O3:Ti, Y2SiO5:Ce (YSO:Ce) or Y3Al5O12:Ce (YAG:Ce). This paper presents the results of research and suggests possible mechanisms as well as processes of radiation changes that occur in scintillators due to irradiation. It also discusses how these effects can affect the scintillation characteristics of composite scintillators exposed to radiation.

A large number of experiments carried out at charged particle accelerators indicate that the radiation dose accumulated by the scintillation materials contained in detectors is significant.For example, in experiments at the Large Hadron Collider, the radiation dose in scintillation detectors can reach 10 Mrad and will increase in the future.In this connection, the search for new radiation-resistant scintillation materials is especially important.Irradiation can significantly alter the characteristics of the scintillator material.The aim of this work was to study the features of possible radiation damage and transformations in composite scintillators under the action of ionizing radiation.We focused on composite scintillators, which are transparent non-luminescent gel-compositions containing grains of scintillation oxide single crystals.A comparative analysis of the spectra of the relative light yield, transmission, and luminescence, as well as their dependence on the accumulated dose for various composite scintillators, has been carried out.Possible mechanisms of radiation changes occurring in scintillators under irradiation are proposed and the influence of these processes on the radiation resistant of composite scintillators is analyzed.In this work, as in previous works in this series, we irradiated composite scintillators on a linear electron accelerator.The electron energy was 10 MeV.We irradiated with a low (0.2 Mrad/h) and a high (1500 Mrad/h) dose rate.At low dose rate, cracking occurs at lower radiation dose values (about 100-200 Mrad) than under irradiation at a high dose rate (up to 500 Mrad).The luminescent characteristics of the scintillator changed insignificantly until the gel composition fixing single-crystal grains cracked.After destruction of the gel composition, an abrupt deterioration in the properties of the sample took place.

CMS hadron calorimeters (HB, HE, HO) have been in operation for several years and contributed substantially to the success of the CMS Physics Program. The endcap calorimeter HE suffered more radiation damage than anticipated causing rapid degradation of scintillator segments (tiles) which have a higher radiation flux from secondary particles than HB and HO. A proposal to upgrade of HE calorimeter will provide a solution for survivability at future LHC higher luminosity. A finger-strip plastic scintillator option has many advantages and is a lower cost alternative to keep the excellent HE performance at high luminosity. Measurements and simulations have been performed and this method is a good upgrade strategy. HE upgrade beyond phase 1. Finger scintillator option. S.V. Afanasiev, P. de Barbaro, A.Yu. Boyarintsev, I.F. Emeliantchik, I.A. Golutvin, B.V. Grinyov, Yu.V. Ershov, L.G. Levchuk , A.V. Litomin, A.I. Malakhov, P.V. Moisenz, V.F. Popov , N.M. Shumeiko, V.A. Smirnov, P.V. Sorokin, P.N. Zhmurin a Joint Institute for Nuclear Research, Dubna, Russia b National Scientific Center, Kharkov Institute of Physics and Technology, Kharkov, Ukraine c Institute for Scintillation Materials National Academy of Sciences of Ukraine, Kharkov, Ukraine d National Center for Particle and High Energy Physics, Minsk, Belarus e University of Rochester, Rochester, USA Abstract CMS hadron calorimeters (HB, HE, HO) have been in operation for several years and contributed substantially to the success of the CMS Physics Program. The endcap calorimeter HE suffered more radiation damage than anticipated causing rapid degradation of scintillator segments (tiles) which have a higher radiation flux from secondary particles than HB and HO. A proposal to upgrade of HE calorimeter will provide a solution for survivability at future LHC higher luminosity. A finger-strip plastic scintillator option has many advantages and is a lower cost alternative to keep the excellent HE performance at high luminosity. Measurements and simulations have been performed and this method is a good upgrade strategy.CMS hadron calorimeters (HB, HE, HO) have been in operation for several years and contributed substantially to the success of the CMS Physics Program. The endcap calorimeter HE suffered more radiation damage than anticipated causing rapid degradation of scintillator segments (tiles) which have a higher radiation flux from secondary particles than HB and HO. A proposal to upgrade of HE calorimeter will provide a solution for survivability at future LHC higher luminosity. A finger-strip plastic scintillator option has many advantages and is a lower cost alternative to keep the excellent HE performance at high luminosity. Measurements and simulations have been performed and this method is a good upgrade strategy.

Problems associated with storage, processing and analysis of data arrays expected in experiments planned at the Large Hadron Collider (LHC) are discussed. These challenges are supposed to be met through a distributed computing model, LHC computing Grid (LCG). Peculiarities of LCG middleware deployment at small computer systems are discussed. Details concerning configuration of the LCG middleware at the KIPT CMS cluster are presented.

The article analyzes two main hypotheses describing the cracking of a composite scintillator in the irradiation zone. This is the "temperature" and "radiation-chemical" hypothesis of cracking. The analysis is based on experi-mental data that we obtained by irradiating scintillators and the results of model chemical experiments.

Two CMS Endcap hadron calorimeters (HE) have been in operation for several years and contributed substantially to the success of the CMS Physics Program. The HE calorimeter suffered more from the radiation than it had been anticipated because of rapid degradation of scintillator segments (tiles) which have a high radiation flux of secondary particles. Some investigations of scintillators have shown that the degradation of plastic scintillator increases significantly at low dose rates. A proposal to upgrade up-grade the HE calorimeter has been prepared to provide a solution for survivability of the future LHC at higher luminosity and higher energy. A finger-strip plastic scintillator option has many advantages and is a lower cost alternative to keep the excellent HE performance at high luminosity. Measurements have been performed and this method has proved to be a good upgrade strategy.

The Compact Muon Solenoid (CMS) is a high-performance general-purpose detector at the Large Hadron Collider (LHC) at CERN.More than twenty institutes from Russia and Joint Institute for Nuclear Research (JINR) are involved in Russia and Dubna Member States (RDMS) CMS Collaboration.A proper computing grid-infrastructure has been constructed at the RDMS institutes for the participation in the running phase of the CMS experiment.Current status of RDMS CMS computing and plans of its development to the next LHC start in 2015 are presented.

Possible reasons for cracking of composite scintillators after irradiation in an electron accelerator at a high dose rate are proposed. The main causes of cracking of composite scintillators, such as ionizing radiation and thermal expansion, are considered. Ionizing radiation can affect the polymer part of the composite scintillator, while thermal expansion mainly affects the crystal grains. A possible mechanism of cracking the composite scintillator during high dose rate irradiation is described.

Summary The report focuses on the innovation technology based on an integral spectral-velocity forecast (ISVF) of reservoir properties types of geological section and filtration-capacitive properties of reservoirs in borehole area. The physical basis of technology, it’s description and flowchart are also introduced there. The application of ISVF technology provides an opportunity to complete the forecast of types of geological section and filtrationcapacitive properties of reservoirs (such as rate of porosity, permeability, effective thickness, specific capacity and hydroconductivity) in the form of prediction maps and 3D cubes. Nowadays, the technology has been tested and used in various geological conditions during carrying out regional and prospecting and exploration seismic works.

The hardware configuration and cluster software of the NSC KIPT specialized Linux cluster constructed for carrying out work on CMS physics simulations and data processing are described. The performances and architecture of the cluster are outlined. The results of participation of NSC KIPT in the CERN/CMS Monte-Carlo event production arc presented.

Розглянуто вимоги, що викликані фізичними цілями експериментів на LHC, які висувають на передній план концепцію розгалуженного зберігання (базується на Grid) та обробки великих масивів експериментальної інформації. Розглянуто функціювання виконуючої пакетної системи на CMS Linux кластері ННЦ ХФТІ. Викладено заходи щодо підготовки кластера до його інтеграції в структури Grid.

The article analyzes two main hypotheses describing the cracking of a composite scintillator in the irradiation zone. This is the "temperature" and "radiation-chemical" hypothesis of cracking. The analysis is based on experi-mental data that we obtained by irradiating scintillators and the results of model chemical experiments.

The first (e,e'p) polarization transfer measurements on a nucleus heavier than deuterium have been carried out at Jefferson Laboratory. Transverse and longitudinal components of the polarization of protons ejected in the reaction 16O(e,e'p) were measured in quasielastic perpendicular kinematics at a Q^2 of 0.8 (GeV/c)^2. The data are in good agreement with state of the art calculations, but do not exclude possible changes in the ratio of the electric to magnetic form factors of the nucleon in the nuclear medium at the level of recent theoretical predictions.

In conformity with the Agreement of 03.04.1993 between the Government of Ukraine and CERN, the National Science Center Kharkov Institute of Physics & Technology (NSC KIPT) takes part in the international CMS program. Its collaboration duties include: the manufacture of scintillation elements for the forward hadron calorimeter and investigation of their characteristics; the simulation of physical processes in the CMS detector; the preparation for processing experimental results. PACS: 07.77.Ka.

As a part of the spin-physics program at the Jefferson Laboratory (TJNAF), a Moller polarimeter has been developed to measure the polarization of electron beam of energies between 0.8 and 6.0 GeV. A unique design of this polarimeter was developed using a set of three quadrupole magnets that provide an angular selection of the Moller electron pairs, a dipole magnet for their energy analysis, an a rotatable target system. The test procedure and commissioning of the polarimeter are presented. The results of beam polarization measurements in long-term physical experiments, the correlation for the three-beam accelerator mode and other effects are discussed.

As part of the spin physics program at Jefferson Laboratory (JLab), a Møller polarimeter was developed to measure the polarization of electron beam of energies 0.8 to 5.0 GeV. A unique signature for Møller scattering is obtained using a series of three quadrupole magnets which provide an angular selection, and a dipole magnet for energy analysis. The design, commissioning, and the first results of the polarization measurements of this polarimeter will be presented as well as future plans to use its small scattering angle capabilities to investigate physics in the very low $Q^2$ regime.