4,842 research outputs found

    Correlated D-meson decays competing against thermal QGP dilepton radiation

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    The QGP that might be created in ultrarelativistic heavy-ion collisions is expected to radiate thermal dilepton radiation. However, this thermal dilepton radiation interferes with dileptons originating from hadron decays. In the invariant mass region between the ϕ\phi and J/ΨJ/\Psi peak (11\,GeVM+3\lesssim M_{\ell^+ \ell^-} \lesssim 3 \,GeV) the most substantial background of hadron decays originates from correlated DDˉ\bar{\mathrm{D}}-meson decays. We evaluate this background using a Langevin simulation for charm quarks. As background medium we utilize the well-tested UrQMD-hybrid model. The required drag and diffusion coefficients are taken from a resonance approach. The decoupling of the charm quarks from the hot medium is performed at a temperature of 130130\,MeV and as hadronization mechanism a coalescence approach is chosen. This model for charm quark interactions with the medium has already been successfully applied to the study of the medium modification and the elliptic flow at FAIR, RHIC and LHC energies. In this proceeding we present our results for the dilepton radiation from correlated DDˉ\bar{\mathrm{D}} decays at RHIC energy in comparison to PHENIX measurements in the invariant mass range between 1 and 3 GeV using different interaction scenarios. These results can be utilized to estimate the thermal QGP radiation.Comment: 4 pages, 1 figur

    Magnetic properties of a metal-organic antiferromagnet on a distorted honeycomb lattice

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    For temperatures T well above the ordering temperature T*=3.0+-0.2K the magnetic properties of the metal-organic material Mn[C10H6(OH)(COO)]2x2H20 built from Mn^2+ ions and 3-hydroxy-2-naphthoic anions can be described by a S=5/2 quantum antiferromagnet on a distorted honeycomb lattice with two different nearest neighbor exchange couplings J2 \approx 2J1 \approx 1.8K. Measurements of the magnetization M(H,T) as a function of a uniform external field H and of the uniform zero field susceptibility \chi(T) are explained within the framework of a modified spin-wave approach which takes into account the absence of a spontaneous staggered magnetization at finite temperatures.Comment: 11 pages, 11 figures; more thorough discussion of the dependence of the correlation length on the uniform magnetic field adde

    OpenML Benchmarking Suites

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    Machine learning research depends on objectively interpretable, comparable, and reproducible algorithm benchmarks. Therefore, we advocate the use of curated, comprehensive suites of machine learning tasks to standardize the setup, execution, and reporting of benchmarks. We enable this through software tools that help to create and leverage these benchmarking suites. These are seamlessly integrated into the OpenML platform, and accessible through interfaces in Python, Java, and R. OpenML benchmarking suites are (a) easy to use through standardized data formats, APIs, and client libraries; (b) machine-readable, with extensive meta-information on the included datasets; and (c) allow benchmarks to be shared and reused in future studies. We also present a first, carefully curated and practical benchmarking suite for classification: the OpenML Curated Classification benchmarking suite 2018 (OpenML-CC18)
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