108 research outputs found

    The Effect of Interface Texture on Exchange Biasing in Ni80Fe20/Ir20Mn80System

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    Exchange-biasing phenomenon can induce an evident unidirectional hysteresis loop shift by spin coupling effect in the ferromagnetic (FM)/antiferromagnetic (AFM) interface which can be applied in magnetoresistance random access memory (MRAM) and recording-head applications. However, magnetic properties are the most important to AFM texturing. In this work, top-configuration exchange-biasing NiFe/IrMn(x Å) systems have been investigated with three different conditions. From the high-resolution cross-sectional transmission electron microscopy (HR X-TEM) and X-ray diffraction results, we conclude that the IrMn (111) texture plays an important role in exchange-biasing field (Hex) and interfacial exchange energy (Jk).HexandJktend to saturate when the IrMn thickness increases. Moreover, the coercivity (Hc) dependence on IrMn thickness is explained based on the coupling or decoupling effect between the spins of the NiFe and IrMn layers near the NiFe/IrMn interface. In this work, the optimal values forHexandJkare 115 Oe and 0.062 erg/cm2, respectively

    An upper limit on hypertriton production in collisions of Ar(1.76 AGeV)+KCl

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    A high-statistic data sample of Ar(1.76 AGeV)+KCl events recorded with HADES is used to search for a hypertriton signal. An upper production limit per centrality-triggered event of 1.041.04 x 10310^{-3} on the 3σ3\sigma level is derived. Comparing this value with the number of successfully reconstructed Λ\Lambda hyperons allows to determine an upper limit on the ratio NΛ3H/NΛN_{_{\Lambda}^3H}/N_{\Lambda}, which is confronted with statistical and coalescence-type model calculations

    Deep sub-threshold Ξ\Xi^- production in Ar+KCl reactions at 1.76A GeV

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    We report first results on a deep sub-threshold production of the doubly strange hyperon Ξ\Xi^- in a heavy-ion reaction. At a beam energy of 1.76A GeV the reaction Ar+KCl was studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18/GSI. A high-statistics and high-purity Λ\Lambda sample was collected, allowing for the investigation of the decay channel ΞΛπ\Xi^- \to \Lambda \pi^-. The deduced Ξ/(Λ+Σ0)\Xi^-/(\Lambda+\Sigma^0) production ratio of (5.6±1.21.7+1.8)103(5.6 \pm 1.2 ^{+1.8}_{-1.7})\cdot 10^{-3} is significantly larger than available model predictions.Comment: 4 pages, including 4 figure

    Study of the quasi-free npnpπ+πnp \to np \pi^+\pi^- reaction with a deuterium beam at 1.25 GeV/nucleon

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    The tagged quasi-free npnpπ+πnp \to np\pi^+\pi^- reaction has been studied experimentally with the High Acceptance Di-Electron Spectrometer (HADES) at GSI at a deuteron incident beam energy of 1.25 GeV/nucleon (s\sqrt s \sim 2.42 GeV/c for the quasi-free collision). For the first time, differential distributions for π+π\pi^{+}\pi^{-} production in npnp collisions have been collected in the region corresponding to the large transverse momenta of the secondary particles. The invariant mass and angular distributions for the npnpπ+πnp\rightarrow np\pi^{+}\pi^{-} reaction are compared with different models. This comparison confirms the dominance of the tt-channel with ΔΔ\Delta\Delta contribution. It also validates the changes previously introduced in the Valencia model to describe two-pion production data in other isospin channels, although some deviations are observed, especially for the π+π\pi^{+}\pi^{-} invariant mass spectrum. The extracted total cross section is also in much better agreement with this model. Our new measurement puts useful constraints for the existence of the conjectured dibaryon resonance at mass M\sim 2.38 GeV and with width Γ\Gamma\sim 70 MeV

    Inclusive dielectron production in proton-proton collisions at 2.2 GeV beam energy

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    Data on inclusive dielectron production are presented for the reaction p+p at 2.2 GeV measured with the High Acceptance DiElectron Spectrometer (HADES). Our results supplement data obtained earlier in this bombarding energy regime by DLS and HADES. The comparison with the 2.09 GeV DLS data is discussed. The reconstructed e+e- distributions are confronted with simulated pair cocktails, revealing an excess yield at invariant masses around 0.5 GeV/c2. Inclusive cross sections of neutral pion and eta production are obtained

    Inclusive Dielectron Production in Ar+KCl Collisions at 1.76 AGeV studied with HADES

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    Results of the HADES measurement of inclusive dielectron production in Ar+KCl collisions at a kinetic beam energy of 1.76 AGeV are presented. For the first time, high mass resolution spectroscopy was performed. The invariant mass spectrum of dielectrons is compared with predictions of UrQMD and HSD transport codes.Comment: 4 pages, 3 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse

    In-Medium Effects on K0 Mesons in Relativistic Heavy-Ion Collisions

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    We present the transverse momentum spectra and rapidity distributions of π\pi^{-} and KS0^0_S in Ar+KCl reactions at a beam kinetic energy of 1.756 A GeV measured with the spectrometer HADES. The reconstructed KS0^0_S sample is characterized by good event statistics for a wide range in momentum and rapidity. We compare the experimental π\pi^{-} and KS0^0_S distributions to predictions by the IQMD model. The model calculations show that KS0^0_S at low tranverse momenta constitute a particularly well suited tool to investigate the kaon in-medium potential. Our KS0^0_S data suggest a strong repulsive in-medium K0^0 potential of about 40 MeV strength.Comment: 10 pages, 10 figures, accepted by Phys. Rev.

    Future perspectives at SIS-100 with HADES-at-FAIR

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    Currently, the HADES spectrometer undergoes un upgrade program to be prepared for measurements at the upcoming SIS-100 synchrotron at FAIR. We describe the current status of the HADES di-electron measurements at the SIS-18 and our future plans for SIS-100.Comment: Invited contribution presented at the XLVII International Winter Meeting on Nuclear Physics, Bormio (Italy), Jan. 26-30, 200
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