1,355 research outputs found

    Comment on "Material Evidence of a 38 MeV Boson"

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    In the recent preprint 1202.1739 it was claimed that preliminary data presented by COMPASS at recent conferences confirm the existence of a resonant state of mass 38 MeV decaying to two photons. This claim was made based on structures observed in two-photon mass distributions which however were shown only to demonstrate the purity and mass resolution of the {\pi}0 and {\eta} signals. The additional structures are understood as remnants of secondary interactions inside the COMPASS spectrometer. Therefore, the COMPASS data do not confirm the existence of this state.Comment: 2 pages, 7 figure

    Angular Correlations in Internal Pair Conversion of Aligned Heavy Nuclei

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    We calculate the spatial correlation of electrons and positrons emitted by internal pair conversion of Coulomb excited nuclei in heavy ion collisions. The alignment or polarization of the nucleus results in an anisotropic emission of the electron-positron pairs which is closely related to the anisotropic emission of γ\gamma-rays. However, the angular correlation in the case of internal pair conversion exhibits diverse patterns. This might be relevant when investigating atomic processes in heavy-ion collisions performed at the Coulomb barrier.Comment: 27 pages + 6 eps figures, uses revtex.sty and epsf.sty, tar-compressed and uuencoded with uufile

    Climate informed engineering: An essential pillar of industry 4.0 transformation

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    Breakthroughs in computing have led to development of new generations of Earth Systems Models providing detailed information on how our planet may locally respond to the ongoing global warming. Access to such climate information systems presents an unprecedented opportunity for engineers to make tangible contributions to climate adaptation through integration of climate information in their products, designs, and services. We introduce the concept of “Climate Informed Engineering” (CIE) as an emerging interdisciplinary field integrating climatic considerations in engineering products and services. The concept behind CIE is to enable engineers to build infrastructure, devices, sensors or develop new materials and processes that are informed by climate and climate change information. We believe CIE will be an increasingly important dimension of Engineering Science resonating with engineers and scientists with different backgrounds

    Measurement of the 187Re({\alpha},n)190Ir reaction cross section at sub-Coulomb energies using the Cologne Clover Counting Setup

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    Uncertainties in adopted models of particle+nucleus optical-model potentials directly influence the accuracy in the theoretical predictions of reaction rates as they are needed for reaction-network calculations in, for instance, {\gamma}-process nucleosynthesis. The improvement of the {\alpha}+nucleus optical-model potential is hampered by the lack of experimental data at astrophysically relevant energies especially for heavier nuclei. Measuring the Re187({\alpha},n)Ir190 reaction cross section at sub-Coulomb energies extends the scarce experimental data available in this mass region and helps understanding the energy dependence of the imaginary part of the {\alpha}+nucleus optical-model potential at low energies. Applying the activation method, after the irradiation of natural rhenium targets with {\alpha}-particle energies of 12.4 to 14.1 MeV, the reaction yield and thus the reaction cross section were determined via {\gamma}-ray spectroscopy by using the Cologne Clover Counting Setup and the method of {\gamma}{\gamma} coincidences. Cross-section values at five energies close to the astrophysically relevant energy region were measured. Statistical model calculations revealed discrepancies between the experimental values and predictions based on widely used {\alpha}+nucleus optical-model potentials. However, an excellent reproduction of the measured cross-section values could be achieved from calculations based on the so-called Sauerwein-Rauscher {\alpha}+nucleus optical-model potential. The results obtained indicate that the energy dependence of the imaginary part of the {\alpha}+nucleus optical-model potential can be described by an exponential decrease. Successful reproductions of measured cross sections at low energies for {\alpha}-induced reactions in the mass range 141{\leq}A{\leq}187 confirm the global character of the Sauerwein-Rauscher potential

    Meson spectroscopy with COMPASS

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    The COMPASS fixed-target experiment at CERN SPS is dedicated to the study of hadron structure and dynamics. In the physics programme using hadron beams, the focus is on the detection of new states, in particular the search for JPCJ^{PC} exotic states and glueballs. After a short pilot run in 2004 (190 GeV/c negative pion beam, lead target), we started our hadron spectroscopy programme in 2008 by collecting an unprecedented statistics with a negative hadron beam (190 GeV/c) on a liquid hydrogen target. A similar amount of data with positive hadron beam (190 GeV/c) has been taken in 2009, as well as some additional data with negative beam on nuclear targets. The spectrometer features a large angular acceptance and high momentum resolution and also good coverage by electromagnetic calorimetry, crucial for the detection of final states involving π0\pi^0 or η\eta. A first important result is the observation of a significant JPCJ^{PC} spin exotic signal consistent with the disputed π1(1600)\pi_1(1600) in the pilot run data. This result was recently published. We present an overview of the status of various ongoing analyses on the 2008/09 data.Comment: 6 pages, 6 figures, to appear in the proceedings of the International Nuclear Physics Conference 2010, Vancouver, Canada, 04-09 Jul 201

    Derivation of Boltzmann Principle

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    We present a derivation of Boltzmann principle SB=kBlnWS_{B}=k_{B}\ln \mathcal{W} based on classical mechanical models of thermodynamics. The argument is based on the heat theorem and can be traced back to the second half of the nineteenth century with the works of Helmholtz and Boltzmann. Despite its simplicity, this argument has remained almost unknown. We present it in a modern, self-contained and accessible form. The approach constitutes an important link between classical mechanics and statistical mechanics
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