Effect of pressure on the superconducting Tc of MgB2

Measurements of the superconducting transition temperature Tc have been performed by the inductive method on MgB2 at pressures up to 28 GPa. Tc decreases with applied pressure, exhibiting a cusp at about 9 GPa. We interpret the appearance of this anomaly in the Tc(P) dependence as a result of the pressure-induced electronic transition. Recent band-structure calculations for MgB2 give some support for such an explanation.Comment: 11 pages, including 4 figure

Experiments on electromagnetic interaction of linearly polarized photons with nucleons and nuclei

Experiments on electromagnetic interaction of nucleons and nuclei with linearly polarized photon beams produced by coherent bremsstrahlung of high energy electrons from diamond single crystal targets are reviewed. The details of experimental equipment, the methods of beam monitoring and photon polarization evaluation, as well as the methods for measuring cross section asymmetries are discussed. The experimental results for polarization parameters of pion photoproduction and photodisintegration reactions are presented and discussed along with theoretical analyses.Розглянуто експерименти з електромагнітної взаємодії нуклонів та ядер з лінійно поляризованими фотонними пучками, які отримані в результаті когерентного випромінювання електронів з високими енергіями на мішені з кристалу алмаза. Дискутуються деталі експериментального обладнання, методи моніторування пучка та визначення величини поляризації фотонів, а також методи вимірювання асиметрії перерізів. Експериментальні результати для поляризаційних параметрів фото народження піонів та реакцій фото дезінтеграції, що представлені, дискутуються наразі з теоретичним аналізом.Рассмотрены эксперименты по электромагнитному взаимодействию нуклонов и ядер с линейно поляризованными фотонными пучками, производимыми в результате когерентного тормозного излучения электронов с высокими энергиями на мишени из кристалла алмаза. Обсуждаются детали экспериментального оборудования, методы мониторирования пучка и определения величины поляризации фотонов, а также методы измерения асимметрии сечений. Представленные экспериментальные результаты для поляризационных параметров фоторождения пионов и реакций фотодезинтеграции обсуждаются наряду с теоретическим анализом

Effect of Bias Fields on off-Diagonal Magnetoimpedance (MI) Sensor Performance

This paper investigates the performance of off-diagonal magnetoimpedance in Co-based amorphous wire subjected to dc bias fields: circular and orthogonal (with respect to the wire axis). Typically it is as-sumed that the wire impedance is insensitive to the orthogonal field so the wire element can be used to construct 3D sensors. Our results demonstrated the possibility of large impedance change due to this field, in the range of 10 mV/Oe. The dc current in a wire generating a circular field results in improved sensitivi-ty due to elimination of the domain structure and smoothing the effect of the anisotropy deviations. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3633

Влияние лазерного облучения на микроструктуру поверхности сплавов циркония

Представлены результаты исследования влияния лазерного импульсного (длительностью 50 нс) облучения на структуру поверхностных слоев сплавов циркония. В результате лазерного облучения поверхности циркониевых сплавов формируются аморфные фазы, концентрация включений интерметаллических фаз в поверхностном слое глубиной до 0,3 мкм уменьшается почти вдвое. На поверхности сплавов формируются волновые структуры за счет быстрого застывания жидкого расплава, фронт которого движется с большой скоростью вследствие возможной неустойчивости Кельвина-Гельмгольца или возникновения кристаллизационных волн на поверхности облученного пятна. The results of studying the effect of laser pulse (duration 50 ns) irradiation on the structure of the surface layers of zirconium alloys. As a result of laser irradiation of the zirconium alloys surface are formed amorphous phases, the concentration of inclusions of intermetallic phases in the surface layer depth of 0.3 microns is reduced by almost half. On the surface alloys formed by the wave structure due to the rapid solidification of the liquid melt, whose front is moving at high speed due to possible Kelvin-Helmholtz instability or the occurrence of crystallization waves at the surface irradiated spot. Представлені результати дослідження впливу лазерного імпульсного (тривалістю 50 нс) опромінення на структуру поверхневих шарів сплавів цирконію. У результаті лазерного опромінення поверхні цирконієвих сплавів формуються аморфні фази, концентрація включень інтерметалевих фаз в поверхневому шарі глибиною до 0,3 мкм зменшується майже вдвічі. На поверхні сплавів формуються хвильові структури за рахунок швидкого застигання рідкого розплаву, фронт якого рухається з великою швидкістю внаслідок можливої нестійкості Кельвіна-Гельмгольца або виникнення кристалізаційних хвиль на поверхні опроміненого плями

Structure and Stresses in a System of Two Mechanical Twins in Titanium

In the work we have presented the results of experimental studies and mathematical modeling for the processes of the structure formation in a transition zone of wedge-type twins system in commercially pure titanium. The process of interaction of structure defects with twinning dislocations during the formation of a wedge-type twin was taken into consideration. It is shown that the interaction alters the stress maximum in vicinity of boundaries in the system two wedge-type twins

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters

Measurement of D*+/- meson production in jets from pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

This paper reports a measurement of D*+/- meson production in jets from proton-proton collisions at a center-of-mass energy of sqrt(s) = 7 TeV at the CERN Large Hadron Collider. The measurement is based on a data sample recorded with the ATLAS detector with an integrated luminosity of 0.30 pb^-1 for jets with transverse momentum between 25 and 70 GeV in the pseudorapidity range |eta| < 2.5. D*+/- mesons found in jets are fully reconstructed in the decay chain: D*+ -> D0pi+, D0 -> K-pi+, and its charge conjugate. The production rate is found to be N(D*+/-)/N(jet) = 0.025 +/- 0.001(stat.) +/- 0.004(syst.) for D*+/- mesons that carry a fraction z of the jet momentum in the range 0.3 < z < 1. Monte Carlo predictions fail to describe the data at small values of z, and this is most marked at low jet transverse momentum.Comment: 10 pages plus author list (22 pages total), 5 figures, 1 table, matches published version in Physical Review