$\hat{I}{\pounds }^0$ production in proton nucleus collisions near threshold

Abstract

The production of $\hat{I}{\pounds }^0$ 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. $\hat{I}{\pounds }^0$s were identified via the decay $\hat{I}{\pounds }^0\to \hat{I}›{\hat{I}}^3$ with subsequent decays $\hat{I}›\to p\ddot{I}{€}^{-}$ in coincidence with a $e^{+}{e}^{-}$ pair from either external (${\hat{I}}^3\to e^{+}{e}^{-}$) or internal (Dalitz decay $γ^{*}\rightarrow e^{+} e^{-}$) gamma conversions. The differential $\hat{I}{\pounds }^0$ cross section integrated over the detector acceptance, i.e. the rapidity interval $0.5<y<1.1$, has been extracted as $\hat{I}”\ddot{I}{ƒ}_{\hat{I}{\pounds }^0}=2.3\pm (0.2{)}^{stat}\pm {\left({}_{-0.6}^{+0.6}\right)}^{sys}\pm (0.2{)}^{norm}$ mb, yielding the inclusive production cross section in full phase space $\ddot{I}{ƒ}_{\hat{I}{\pounds }^0}^{total}=5.8\pm (0.5{)}^{stat}\pm {\left({}_{-1.4}^{+1.4}\right)}^{sys}\pm (0.6{)}^{norm}\pm (1.7{)}^{extrapol}$ mb by averaging over different extrapolation methods. The $\hat{I}{›}_{all}$/$\hat{I}{\pounds }^0$ 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 $\hat{I}{\pounds }^0$ yield agrees with the statistical model of particle production in nuclear reactions.

7 pages, 5 figures