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Institute
his contribution aims to give a basic overview of the latest results regarding the production of resonances in different collision systems. The results were extracted from experimental data collected with HADES that is a multipurpose detector located at the GSI Helmholtzzentrum, Darmstadt. The main points discussed here are: the properties of the strange resonances Λ(1405) and Σ(1385), the role of Δ’s as a source of pions in the final state, the production dynamics reflected in form of differential cross sections, and the role of the ϕ meson as a source for K− particles.
The production of Σ0 baryons in the nuclear reaction p (3.5 GeV) + Nb (corresponding to sNN=3.18 GeV) is studied with the detector set-up HADES at GSI, Darmstadt. Σ0s were identified via the decay Σ0→Λγ with subsequent decays Λ→pπ− in coincidence with a e+e− pair from either external (γ→e+e−) or internal (Dalitz decay γ⁎→e+e−) gamma conversions. The differential Σ0 cross section integrated over the detector acceptance, i.e. the rapidity interval 0.5<y<1.1, has been extracted as ΔσΣ0=2.3±(0.2)stat±(−0.6+0.6)sys±(0.2)norm mb, yielding the inclusive production cross section in full phase space σΣ0total=5.8±(0.5)stat±(−1.4+1.4)sys±(0.6)norm±(1.7)extrapol mb by averaging over different extrapolation methods. The Λall/Σ0 ratio within the HADES acceptance is equal to 2.3±(0.2)stat±(−0.6+0.6)sys. The obtained rapidity and momentum distributions are compared to transport model calculations. The Σ0 yield agrees with the statistical model of particle production in nuclear reactions. Keywords: Hyperons, Strangeness, Proton, Nucleus.
Expectations of Sterling returning to Gold have been disregarded in empirical work on the US dollar – Sterling exchange rate in the early 1920s. We incorporate such considerations in a PPP model of the exchange rate, letting the probability of a return to gold follow a logistic function. We draw several conclusions: (i) the PPP model works well from spring 1919 to spring 1925; (ii) wholesale prices outperform consumer prices; (iii) allowing for a return to gold leads to a higher speed of adjustment of the exchange rate to PPP; (iv) interest rate differentials and the relative monetary base are crucial determinants of the expected return to gold; (v) the probability of a return to Gold peaked at about 72% in late 1924 and but fell to about 60% in early 1925; and (vi) our preferred model does not support the Keynes’ view that Sterling was overvalued after the return to gold.
We test the menu cost model of Ball and Mankiw (1994, 1995), which implies that the impact of price dispersion on inflation should differ between inflation and deflation episodes, using data for Japan and Hong Kong. We use a random cross-section sample split when calculating the moments of the distribution of price changes to mitigate the small-cross-sectionsample bias noted by Cecchetti and Bryan (1999). The parameter on the third moment is positive and significant in both countries during both the inflation and deflation periods, and the parameter on the second moment changes sign in the deflation period, as the theory predicts. Keywords: inflation, deflation, menu costs, Hong Kong, Japan JEL Numbers: E31
We present measurements of exclusive ensuremathπ+,0 and η production in pp reactions at 1.25GeV and 2.2GeV beam kinetic energy in hadron and dielectron channels. In the case of π+ and π0 , high-statistics invariant-mass and angular distributions are obtained within the HADES acceptance as well as acceptance-corrected distributions, which are compared to a resonance model. The sensitivity of the data to the yield and production angular distribution of Δ (1232) and higher-lying baryon resonances is shown, and an improved parameterization is proposed. The extracted cross-sections are of special interest in the case of pp → pp η , since controversial data exist at 2.0GeV; we find \ensuremathσ=0.142±0.022 mb. Using the dielectron channels, the π0 and η Dalitz decay signals are reconstructed with yields fully consistent with the hadronic channels. The electron invariant masses and acceptance-corrected helicity angle distributions are found in good agreement with model predictions.