Long-term operation of a multi-channel cosmic muon system based on scintillation counters with MRS APD light readout

A Cosmic Ray Test Facility (CRTF) is the first large-scale implementation of a scintillation triggering system based on a new scintillation technique known as START. In START, the scintillation light is collected and transported by WLS optical fibers, while light detection is performed by pairs of avalanche photodiodes with the Metal-Resistor-Semiconductor structure operated in the Geiger mode (MRS APD). START delivers 100% efficiency of cosmic muon detection, while its intrinsic noise level is less than 10^{-2} Hz. CRTF, consisting of 160 START channels, has been continuously operated by the ALICE TOF collaboration for more than 25 000 hours, and has demonstrated a high level of stability. Fewer than 10% of MRS APDs had to be replaced during this period.Comment: Proceedings of NDIP-2008. 8 pages, 8 figures, 6 reference

Rearrangement of the vortex lattice due to instabilities of vortex flow

With increasing applied current we show that the moving vortex lattice changes its structure from a triangular one to a set of parallel vortex rows in a pinning free superconductor. This effect originates from the change of the shape of the vortex core due to non-equilibrium effects (similar to the mechanism of vortex motion instability in the Larkin-Ovchinnikov theory). The moving vortex creates a deficit of quasiparticles in front of its motion and an excess of quasiparticles behind the core of the moving vortex. This results in the appearance of a wake (region with suppressed order parameter) behind the vortex which attracts other vortices resulting in an effective direction-dependent interaction between vortices. When the vortex velocity $v$ reaches the critical value $v_c$ quasi-phase slip lines (lines with fast vortex motion) appear which may coexist with slowly moving vortices between such lines. Our results are found within the framework of the time-dependent Ginzburg-Landau equations and are strictly valid when the coherence length $\xi(T)$ is larger or comparable with the decay length $L_{in}$ of the non-equilibrium quasiparticle distribution function. We qualitatively explain experiments on the instability of vortex flow at low magnetic fields when the distance between vortices $a \gg L_{in} \gg \xi (T)$. We speculate that a similar instability of the vortex lattice should exist for $v>v_c$ even when $a<L_{in}$.Comment: 10 pages, 11 figure

Avalanche photodiodes for the CMS electromagnetic calorimeter

Avalanche photodiodes(APD's) will be used as photodetectors in the CMS barrel electromagnetic crystal calorimeter for high precision energy measurements in a hostile radiation environment. Significant progress has been made in the characteristics of these devices being expressly developed for CMS. Parameters of the final structure APD's together with demonstrations of radiation hardness and plans for quality assurance/control during the production phase are presented

Hadron calorimeter with MAPD readout in the NA61/SHINE experiment

The modular hadron calorimeter with micro-pixel avalanche photodiodes readout for the NA61/SHINE experiment at the CERN SPS is presented. The calorimeter consists of 44 independent modules with lead-scintillator sandwich structure. The light from the scintillator tiles is captured by and transported with WLS-fibers embedded in scintillator grooves. The construction provides a longitudinal segmentation of the module in 10 sections with independent MAPD readout. MAPDs with pixel density of $~10^{4}$/mm$^2$ ensure good linearity of calorimeter response in a wide dynamical range. The performance of the calorimeter prototype in a beam test is reported

Scintillator counters with multi-pixel avalanche photodiode readout for the ND280 detector of the T2K experiment

The Tokai-to-Kamioka (T2K) experiment is a second generation long baseline neutrino oscillation experiment which aims at a sensitive search for νe appearance. The main design features of the T2K near neutrino detectors located at 280 m from the target are presented, and the scintillator counters are described. The counters are readout via WLS fibers embedded into S-shaped grooves in the scintillator from both ends by multi-pixel avalanche photodiodes operating in a limited Geiger mode. Operating principles and results of tests of photosensors with a sensitive area of 1 mm2 are presented. A time resolution of 1.75 ns, a spatial resolution of 9.9 - 12.4 cm, and a detection efficiency for minimum ionizing particles of more than 99% were obtained for scintillator detectors in a beam test. © 2007 Elsevier B.V. All rights reserved

Scintillator counters with WLS fiber/MPPC readout for the side muon range detector (SMRD)of the T2K experiment

The T2K neutrino experiment at J-PARC uses a set of near detectors to measure the properties of an unoscillated neutrino beam and neutrino interaction cross-sections. One of the sub-detectors of the near-detector complex, the side muon range detector (SMRD), is described in the paper. The detector is designed to help measure the neutrino energy spectrum, to identify background and to calibrate the other detectors. The active elements of the SMRD consist of 0.7 cm thick extruded scintillator slabs inserted into air gaps of the UA1 magnet yokes. The readout of each scintillator slab is provided through a single WLS fiber embedded into a serpentine shaped groove. Two Hamamatsu multi-pixel avalanche photodiodes (MPPC's) are coupled to both ends of the WLS fiber. This design allows us to achieve a high MIP detection efficiency of greater than 99%. A light yield of 25-50 p.e./MIP, a time resolution of about 1 ns and a spatial resolution along the slab better than 10 cm were obtained for the SMRD counters.Comment: 7 pages, 4 figures; talk at TIPP09, March 12-17, Tsukuba, Japan; to be published in the conference proceeding

Влияние освещения кризиса на финансовый рынок России

The article examines the impact of informational messages characterizing the crisis in the economy on the financial market indicators. The aim of the article is to build an index that allows assessing the crisis situation in the country based on textual analysis of informational messages. Due to the literature review, the factors determining the crisis in the economy were identified. The empirical base of the study included more than 10 million news texts from various sources accredited by Thomson Reuters. For the first time, the authors compiled a “bag of words” (dictionary) to determine the crisis situation in the country; and by means of the text analysis, they developed the author’s crisis index calculated on the basis of news reports in foreign media about Russia. They conducted the analysis of the relations between the crisis index and the stock index MOEX. According to the results of the study, it has been established that an increase in the number of news reports determining the crisis situation in the economy has a negative effect on the financial market: it leads to a drop in stock prices. Thus, not only objective economic factors, but also the information component influencing the mood of investors and the behavior of economic entities, affects the key indicators of the financial market. The proposed author’s crisis index can also be used to assess other relations, for example, the effect of the crisis on the exchange rate.В статье исследуется влияние информационных сообщений, характеризующих проявление кризиса в экономике, на показатели финансового рынка. Цель статьи — построение индекса, позволяющего оценивать кризисную ситуацию в стране на основе текстового анализа информационных сообщений. С помощью обзора литературы выявлены факторы, определяющие кризисные явления в экономике. Эмпирическая база исследования включала в себя более 10 млн новостных текстов из различных источников, аккредитованных ThomsonReuters. Авторы впервые составили «мешок слов» (словарь) для определения кризисной ситуации в стране и с помощью текстового анализа разработали авторский индекс кризиса, рассчитанный на основе новостных сообщений в зарубежных СМИ о России. Проведен анализ зависимости между индексом кризиса и биржевым индексом MOEX. По результатам исследования установлено, что увеличение количества новостных сообщений, определяющих проявление кризисной ситуации в экономике, негативно отражается на финансовом рынке: приводит к падению котировок акций. Таким образом, не только объективные экономические факторы, но и информационная составляющая, оказывающая влияние на настроения инвесторов и поведение экономических субъектов, воздействует на ключевые показатели финансового рынка. Предложенный авторский индекс кризиса может также быть использован для оценки других зависимостей, например влияния кризиса на валютный курс

Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV

The t t-bar production cross section (sigma[t t-bar]) is measured in proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS experiment, corresponding to an integrated luminosity of 2.3 inverse femtobarns. The measurement is performed in events with two leptons (electrons or muons) in the final state, at least two jets identified as jets originating from b quarks, and the presence of an imbalance in transverse momentum. The measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/- 2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction of the standard model.Comment: Replaced with published version. Included journal reference and DO