970 research outputs found

    Measurement of leptonic and hadronic decays of omega- and phi-mesons at RHIC by PHENIX

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    The PHENIX experiment at RHIC measured production of the \omega- and \phi- mesons in p+p, d+Au and Au+Au collisions at \sqrt{s_NN} = 63 and 200 GeV. Particle properties were studied using hadronic and di-electron decay channels. Transverse momentum (mass) spectra measured in different decay modes are found to be in agreement with each other within the errors. Nuclear modification factors R_{AA} measured for both mesons are consistent with results previously obtained for other neutral mesons. Position of the meson mass peaks and their widths reconstructed in hadronic decay channels are in agreement with their properties measured in vacuum.Comment: QM2006 proceedings 4 pages, 3 plot

    Теплофизические свойства и термодеструкция нанокомпозитов, отвержденных в постоянных физических полях

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    З використанням методів диференційної скануючої калориметрії (ДСК) та термогравіметрії були досліджені нанокомпозити складу ЕП-3 % СdO та ЕП-3 % (СdO + ПАн), отверднені за нормальних умов та в постійному магнітному або електричному полях. Показано, що ці чинники впливають на сегментальну рухливість міжвузлових фрагментів зшитого полімеру та на стрибок питомої теплоємності. Взаємодія зовнішнього магнітного поля тільки з дипольними молекулами зразка ЕП-3 % CdO зумовлює часткові зміни в його структурі. Аналітична обробка ДСК-термограм показала, що введення до епоксидної матриці поліаніліну (ПАн) та CdO 3 об. % сприяє зменшенню питомої теплоємності епоксиполімеру (ЕП) на дослідженому температурному інтервалі та, відповідно, зумовлює зростання сегментальної рухливості. ПАн, введений до складу суміші реагентів ЕП-CdO, витісняється у міжфазові шари органо-неорганічної суміші і сприяє їх суміщенню. Ці дані корелюють зі змінами енергій активації залежно від складу нанокомпозитів та умов їх тверднення. Було встановлено каталітичний вплив CdO на піроліз поліепоксидної матриці.By using the methods of DSC, TGA-DTG analysis, we study nanocomposites composition EP-3 % CdO and EP-3 % (CdO + PAn) cured under standard conditions in constant magnetic or electric fields. We show that these factors affect the segmental mobility of interstitial cross-linked polymer fragments and the specific heat jump. The interaction of external magnetic field only with dipole molecules of the sample EP-3 % CdO causes a partial change in its structure. Analytical processing of DSC thermograms showed that introduction of the polyaniline (Pan) and CdO 3 % vol. into epoxy matrix contributes to reduction of the specific heat capacity of epoxy (EP)in the investigated temperature range and thus causes the segmental mobility growth. PAn, introduced into the reagent mixture (EP-CdO) is forced into the interfacial organic-inorganic mixture layers and contributes to their reconciliation. These data correlate with changes in the activation energy depending on the nanocomposites composition and their curing conditions. We discover that the CdO catalytic effect influenced the pyrolysis epoxide matrix.С использованием методов дифференциальной сканирующей калориметрии (ДСК) и термогравиметрии были исследованы нанокомпозиты состава ЭП-3 % СdO и ЭП-3 % (СdO + ПАн), отвержденные при нормальных условиях и в постоянном магнитном или электрическом полях. Показано, что данные факторы влияют на сегментальную подвижность межузловых фрагментов сшитого полимера и на скачок удельной теплоемкости. Взаимодействие внешнего магнитного поля только с дипольными молекулами образца ЭП-3 % CdO обусловливает частичные изменения в его структуре. Аналитическая обработка ДСК-термограмм показала, что введение в эпоксидную матрицу полианилина (ПАн) и CdO 3 об. % способствует уменьшению удельной теплоемкости эпоксиполимера (ЭП) на исследованном температурном интервале и, соответственно, обусловливает рост сегментальной подвижности. ПАн, введенный в состав смеси реагентов ЭП-CdO, вытесняется в межфазные слои органо-неорганической смеси и способствует их совмещению. Эти данные коррелируют с изменениями энергий активации в зависимости от состава нанокомпозитов и условий их отвердения. Было установлено каталитическое влияние CdO на пиролиз полиэпоксидной матрицы

    УПРОЧНЕНИЕ ГРЕБНЕЙ И СНИЖЕНИЕ ИЗНОСА КОЛЕСНЫХ ПАР

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    Reducing of wear and tear of a friction pair wheel-rail is one of the main tasks to increase efficiency of railway rolling stock operation. The authors suggest analysis of technologies of thermic reinforcement of the ridges of wheelsets using comparative tests of locomotives. The results of testing of three techniques of metal working, respectively laser, plasmic and electrocontact, allow to select in the framework of comprehensive tribological approach the most reliable and promising technology.The study has shown that the three technologies have differences as for equipment, consumables, technical conditions and staff qualifications necessary to apply them. There are also differences concerning conditions of heating and cooling of reinforced metal (one-time or cyclic heating) and ecological aspects (light radiation, noise level etc).The reinforced zones differ in distribution of firmness and grain dimensions by depth, kinetics of temporary and residual stress, geometry and consequently in their influence on wear and tear process.Experiments have proved that elecrocontact reinforcement permits to achieve the same results (as for reducing wear of ridges) as the plasmic hardening. When using four band zones of reinforcement the mean intensity of wearing of the ridges with electrocontact reinforcement is higher than the wearing of ridges reinforced with plasma by 0,08 мм/104 kм. If six zones of reinforcement are used, the mean intensity of wearing of the ridges is the same for plasmic and elecrtocontact hardening.The authors suppose that electrocontact technology is more promising as it has more possibilities to positively affect the ridges wearing (by changing geometry of band zones of reinforcement, their number and location in the reinforced zone). But to correctly compare the data it is necessary to economically assess the technologies taking into account all costs resulting in comparably equal rates of wearing of ridges during operation of rolling stock.Существует задача снижения износа пары трения колесо-рельс. С ней связывают одно из главных направлений повышения эффективности эксплуатации подвижного состава железных дорог. Авторы статьи предлагают  анализ используемых для этой  цели технологий термического  упрочнения гребней колесных  пар на основе сравнительных испытаний локомотивов. Результаты  проверки трех способов обработки  металла – лазерного, плазменного и электроконтактного – позволяют выбрать наиболее надежную и перспективную технологию в рамках  комплексного трибологического подхода.

    Nuclear dependence of the transverse single-spin asymmetry in the production of charged hadrons at forward rapidity in polarized p+pp+p, p+p+Al, and p+p+Au collisions at sNN=200\sqrt{s_{_{NN}}}=200 GeV

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    We report on the nuclear dependence of transverse single-spin asymmetries (TSSAs) in the production of positively-charged hadrons in polarized p+pp^{\uparrow}+p, p+p^{\uparrow}+Al and p+p^{\uparrow}+Au collisions at sNN=200\sqrt{s_{_{NN}}}=200 GeV. The measurements have been performed at forward rapidity (1.4<η<2.41.4<\eta<2.4) over the range of 1.8<pT<7.01.8<p_{T}<7.0 GeV/c/c and 0.1<xF<0.20.1<x_{F}<0.2. We observed a positive asymmetry ANA_{N} for positively-charged hadrons in \polpp collisions, and a significantly reduced asymmetry in pp^{\uparrow}+AA collisions. These results reveal a nuclear dependence of charged hadron ANA_N in a regime where perturbative techniques are relevant. These results provide new opportunities to use \polpA collisions as a tool to investigate the rich phenomena behind TSSAs in hadronic collisions and to use TSSA as a new handle in studying small-system collisions.Comment: 303 authors from 66 institutions, 9 pages, 2 figures, 1 table. v1 is version accepted for publication in Physical Review Letters. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm

    Measurements of double-helicity asymmetries in inclusive J/ψJ/\psi production in longitudinally polarized p+pp+p collisions at s=510\sqrt{s}=510 GeV

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    We report the double helicity asymmetry, ALLJ/ψA_{LL}^{J/\psi}, in inclusive J/ψJ/\psi production at forward rapidity as a function of transverse momentum pTp_T and rapidity y|y|. The data analyzed were taken during s=510\sqrt{s}=510 GeV longitudinally polarized pp++pp collisions at the Relativistic Heavy Ion Collider (RHIC) in the 2013 run using the PHENIX detector. At this collision energy, J/ψJ/\psi particles are predominantly produced through gluon-gluon scatterings, thus ALLJ/ψA_{LL}^{J/\psi} is sensitive to the gluon polarization inside the proton. We measured ALLJ/ψA_{LL}^{J/\psi} by detecting the decay daughter muon pairs μ+μ\mu^+ \mu^- within the PHENIX muon spectrometers in the rapidity range 1.2<y<2.21.2<|y|<2.2. In this kinematic range, we measured the ALLJ/ψA_{LL}^{J/\psi} to be 0.012±0.0100.012 \pm 0.010~(stat)~±\pm~0.0030.003(syst). The ALLJ/ψA_{LL}^{J/\psi} can be expressed to be proportional to the product of the gluon polarization distributions at two distinct ranges of Bjorken xx: one at moderate range x0.05x \approx 0.05 where recent RHIC data of jet and π0\pi^0 double helicity spin asymmetries have shown evidence for significant gluon polarization, and the other one covering the poorly known small-xx region x2×103x \approx 2\times 10^{-3}. Thus our new results could be used to further constrain the gluon polarization for x<0.05x< 0.05.Comment: 335 authors, 10 pages, 4 figures, 3 tables, 2013 data. Version accepted for publication by Phys. Rev. D. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm

    Nuclear dependence of the transverse-single-spin asymmetry for forward neutron production in polarized pp++AA collisions at sNN=200\sqrt{s_{_{NN}}}=200 GeV

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    During 2015 the Relativistic Heavy Ion Collider (RHIC) provided collisions of transversely polarized protons with Au and Al nuclei for the first time, enabling the exploration of transverse-single-spin asymmetries with heavy nuclei. Large single-spin asymmetries in very forward neutron production have been previously observed in transversely polarized pp++pp collisions at RHIC, and the existing theoretical framework that was successful in describing the single-spin asymmetry in pp++pp collisions predicts only a moderate atomic-mass-number (AA) dependence. In contrast, the asymmetries observed at RHIC in pp++AA collisions showed a surprisingly strong AA dependence in inclusive forward neutron production. The observed asymmetry in pp++Al collisions is much smaller, while the asymmetry in pp++Au collisions is a factor of three larger in absolute value and of opposite sign. The interplay of different neutron production mechanisms is discussed as a possible explanation of the observed AA dependence.Comment: 315 authors, 8 pages, 4 figures, 1 table. v2 is version accepted for publication in Phys. Rev. Lett. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm
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