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Register a new userInclusive pion and eta production in p+Nb collisions at 3.5 GeV beam energy
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Data on inclusive pion and eta production measured with the dielectron spectrometer HADES in the reaction p+93Nb at a kinetic beam energy of 3.5 GeV are presented. Our results, obtained with the photon conversion method, supplement the rather sparse information on neutral meson production in proton-nucleus reactions existing for this bombarding energy regime. The reconstructed e+e-e+e- transverse-momentum and rapidity distributions are confronted with transport model calculations, which account fairly well for both pi0 and eta production.
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Results on the production of the double-strange cascade hyperon $mathrm{Xi^-}$ are reported for collisions of p,(3.5~GeV),+,Nb, studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18 at GSI Helmholtzzentrum for Heavy-Ion Research, Darmstadt. For the first time, subthreshold $mathrm{Xi^-}$ production is observed in proton-nucleus interactions. Assuming a $mathrm{Xi^-}$ phase-space distribution similar to that of $mathrm{Lambda}$ hyperons, the production probability amounts to $P_{mathrm{Xi^-}}=(2.0,pm0.4,mathrm{(stat)},pm 0.3,mathrm{(norm)},pm 0.6,mathrm{(syst)})times10^{-4}$ resulting in a $mathrm{Xi^-/(Lambda+Sigma^0)}$ ratio of $P_{mathrm{Xi^-}}/ P_{mathrm{Lambda+Sigma^0}}=(1.2pm 0.3,mathrm{(stat)}pm0.4,mathrm{(syst)})times10^{-2}$. Available model predictions are significantly lower than the estimated $mathrm{Xi^-}$ yield.
We present the inclusive invariant-mass, transverse momentum and rapidity distributions of dielectrons (e$^{+}$e$^{-}$ pairs) in p+p interactions at 3.5 GeV beam kinetic energy. In the vector-meson mass region, a distinct peak corresponding to direct $omega$ decays is reconstructed with 2% mass resolution. The data is compared to predictions from three model calculations. Due to the large acceptance of the HADES apparatus for $e^{+}e^{-}$ invariant masses above 0.2 GeV/$c^{2}$ and for transverse pair momenta p$_{t}$ $ <$ 1 GeV/$c$, acceptance corrections are to a large extent model independent. This allows us to extract from dielectron data for the first time at this energy the inclusive production cross sections for light vector mesons. Inclusive production cross sections for $pi^o$ and $eta$ mesons are also reported. The obtained results will serve as an important reference for the study of vector meson production in proton-nucleus and heavy-ion collisions. Furthermore, using this data, an improved value for the upper bound of the branching ratio for direct $eta$ decays into the electron-positron channel is obtained.
Results on $Lambda$ hyperon production are reported for collisions of p(3.5 GeV) + Nb, studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18 at GSI Helmholtzzentrum for Heavy-Ion Research, Darmstadt. The transverse mass distributions in rapidity bins are well described by Boltzmann shapes with a maximum inverse slope parameter of about $90,$MeV at a rapidity of $y=1.0$, i.e. slightly below the center-of-mass rapidity for nucleon-nucleon collisions, $y_{cm}=1.12$. The rapidity density decreases monotonically with increasing rapidity within a rapidity window ranging from 0.3 to 1.3. The $Lambda$ phase-space distribution is compared with results of other experiments and with predictions of two transport approaches which are available publicly. None of the prese
The inclusive production of {Lambda} hyperons in proton-proton collisions at $sqrt{s}$ = 3.18 GeV was measured with HADES at the GSI Helmholtzzentrum fur Schwerionenforschung in Darmstadt. The experimental data are compared to a data-based model for individual exclusive {Lambda} production channels in the same reaction. The contributions of intermediate resonances such as {Sigma}(1385), {Delta}++ or N* are considered in detail. In particular, the result of a partial wave analysis is accounted for the abundant pK$^+${Lambda} final state. Model and data show a reasonable agreement at mid rapidities, while a difference is found for larger rapidities. A total {Lambda} production cross section in p+p collisions at $sqrt{s}$ = 3.18 GeV of {sigma}(pp $to$ {Lambda} + X) = 207.3 $pm$ 1.3 +6.0 -7.3 (stat.) $pm$ 8.4 (syst.) +0.4 -0.5 (model) {mu}b is found.
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.
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