Σ0 production in proton nucleus collisions near threshold

The production of Sigma(0) baryons in the nuclear reaction p (3.5 GeV) + Nb (corresponding to root sNN = 3.18 GeV) is studied with the detector set-up HADES at GSI, Darmstadt. Sigma(0)s were identified via the decay Sigma 0 -> Lambda gamma with subsequent decays Lambda -> p pi(-) in coincidence with a e(+)e(-) pair from either external (gamma -> e(+)e(-)) or internal (Dalitz decay gamma* -> 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 +/- (0.2)(stat) +/- ((+0.6)(-0.6))(sys) +/- (0.2)(norm) mB, yielding the inclusive production cross section in full phase space sigma(total)(Sigma 0) = 5.8 +/- (0.5)(stat) +/- ((+1.4)(-1.4))(sys) +/- (0.6)(norm) +/- (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 +/- (0.2)(stat) +/- ((+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. (C) 2018 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license.