The production of \(\Sigma^{0}\) baryons in the nuclear reaction p (3.5 GeV) + Nb (corresponding to \(\sqrt{s_{NN}}=3.18\) GeV) is studied with the detector set-up HADES at GSI, Darmstadt. ...\(\Sigma^{0}\)s were identified via the decay \(\Sigma^{0} \rightarrow \Lambda \gamma\) with subsequent decays \(\Lambda \rightarrow p \pi^{-}\) in coincidence with a \(e^{+}e^{-}\) pair from either external (\(\gamma \rightarrow e^{+} e^{-}\)) or internal (Dalitz decay \(\gamma^{*}\rightarrow e^{+} e^{-}\)) gamma conversions. The differential \(\Sigma^0\) cross section integrated over the detector acceptance, i.e. the rapidity interval \(0.5 < y < 1.1\), has been extracted as \(\Delta\sigma_{\Sigma^{0}} = 2.3 \pm (0.2)^{stat} \pm \left(^{+0.6}_{-0.6}\right)^{sys} \pm (0.2)^{norm}\) mb, yielding the inclusive production cross section in full phase space \(\sigma^{total}_{\Sigma^{0}} = 5.8 \pm (0.5)^{stat} \pm \left(^{+1.4}_{-1.4}\right)^{sys} \pm (0.6)^{norm} \pm (1.7)^{extrapol}\) mb by averaging over different extrapolation methods. The \(\Lambda_{all}\)/\(\Sigma^{0}\) ratio within the HADES acceptance is equal to 2.3 \(\pm\) \((0.2)^{stat}\) \(\pm\) \((^{+0.6}_{-0.6})^{sys}\). The obtained rapidity and momentum distributions are compared to transport model calculations. The \(\Sigma^{0}\) yield agrees with the statistical model of particle production in nuclear reactions.
We report on the first measurement of \(p\Lambda\) and \(pp\) correlations via the femtoscopy method in p+Nb reactions at \(\mathrm{\sqrt{s_{NN}}=3.18} ~\mathrm{GeV}\), studied with the High ...Acceptance Di-Electron Spectrometer (HADES). By comparing the experimental correlation function to model calculations, a source size for \(pp\) pairs of \(r_{0,pp}=2.02 \pm 0.01(\mathrm{stat})^{+0.11}_{-0.12} (\mathrm{sys}) ~\mathrm{fm}\) and a slightly smaller value for \(p\Lambda\) of \(r_{0,\Lambda p}=1.62 \pm 0.02(\mathrm{stat})^{+0.19}_{-0.08}(\mathrm{sys}) ~\mathrm{fm}\) is extracted. Using the geometrical extent of the particle emitting region, determined experimentally with \(pp\) correlations as reference together with a source function from a transport model, it is possible to study different sets of scattering parameters. The \(p\Lambda\) correlation is proven sensitive to predicted scattering length values from chiral effective field theory. We demonstrate that the femtoscopy technique can be used as valid alternative to the analysis of scattering data to study the hyperon-nucleon interaction.
The HADES-at-FAIR project Lapidus, K.; Agakishiev, G.; Balanda, A. ...
Physics of atomic nuclei,
05/2012, Letnik:
75, Številka:
5
Journal Article
Recenzirano
Odprti dostop
After the completion of the experimental program at SIS18 the HADES setup will migrate to FAIR, where it will deliver high-quality data for heavy-ion collisions in an unexplored energy range of up to ...8
A
GeV. In this contribution, we briefly present the physics case, relevant detector characteristics and discuss the recently completed upgrade of HADES.
