Berger-Chen, J.-C.

Fabbietti, L.

Lapidus, K.

GSI Repository

Constraining K0 production channels in proton-proton collisionsfor transport models∗J.-C. Berger-Chen1, L. Fabbietti1, K. Lapidus†1, and the HADES Collaboration1Excellence Cluster “Universe”, TU Mu¨nchen, Boltzmannstr. 2, 85748 Garching, GermanyThe HADES collaboration performed measurements ofstrangeness production in p+p and p+93Nb collisions ata beam kinetic energy of 3.5 GeV. The analysis of theK0-meson emission in p+Nb collisions aims to refine theknowledge of the kaon in-medium behaviour in terms ofthe repulsive potential and the in-medium kaon-nucleonscattering cross sections. The tool to extract these char-acteristics is a transport code incorporating kaon produc-tion mechanisms and kaon final state interactions with nu-clear environment. The measurement of kaons in p+p col-lisions serves as an important reference, which allows toconstrain production cross sections of the different finalstates in transport models.Spectra of kaons produced in p+p collisions were com-pared with the GiBUU [1] simulations based on the res-onance model by Tsushima et al. [2]. In this model,all hyperon-kaon pairs are products of the nucleon res-onances decays, e.g. N(1650) → Λ + K . The res-onance model incorporates all possible channels of typeB + B → B + Y + K , where B can be either a nucleonor a Δ(1232)-resonance, Y is a hyperon (Λ or Σ) and Kstands for a positively charged or a neutral kaon. It wasshown that for the case of inclusive K 0 production in p+preactions the resonance model significantly overestimatesthe K0 yield.A systematical comparison of the various kaon pro-duction channels, implemented in the resonance model,with available published data shows that: i) the channelpπ+ΛK0 is significantly overestimated by the resonancemodel; ii) the channel pΣ+K0 is slightly overestimated aswell.Besides overestimation of the major K 0 productionchannels, the resonance model [2] has other shortcom-ings. One of the main assumptions of the model is that allnucleon-nucleon reactions with the pion in the final state(N + N → N + π + Y + K) proceed through an in-termediate Δ(1232)-resonance with its subsequent decayΔ(1232) → N + π. These final states can be, however,produced in a non-resonant way as well. An on-goinganalysis of the exclusive kaon production in the reactionp+ p → p+ π+ +K0 + Y allows to disentangle the twoproduction mechanisms. The missing mass to the recon-structed pπ+π−π+ system after pre-selection of K 0 can-didates (accessible via K0S → π+π− decays) is shown onFig. 1. The three peaks correspond to the missed neutron(background reaction p + p → p + n + π+ + π+ + π−),∗Work supported by the grants BMBF (06MT9156) and VH-NG-330† kirill.lapidus@ph.tum.deΛ(1116)- and Σ0(1192)-hyperon. A further inspection ofthe pπ+ invariant mass distribution will allow to separatetwo production mechanisms (with or without intermediateΔ(1232)++ state).]2) [MeV/c-π,+π,+πMM(p,0 500 1000 1500dN/dM [a. u.]00.20.40.6nΛ0ΣFigure 1: Distribution of the missing mass to pπ+π+π−-system. Peaks marked “n”, “Λ” and “Σ0” originate fromreactions p + p → p + n + π+ + π+ + π−, p + p →p + π+ + Λ + K0 and p + p → p + π+ + Σ0 + K0,respectively.After taking into account the experimentally obtainedconstraints on the kaon production in elementary collisions,tuned transport models can be used to simulate proton-nucleus and nucleus-nucleus collisions. This will lead tothe reliable determination of in-medium characteristics ofkaon-nucleon interactions. Further information is expectedfrom on-going investigations of other strange particles (Λ,φ(1020), K∗(892)) produced in p+p and p+Nb reactions.References[1] O. Buss et al., “Transport-theoretical Description of NuclearReactions”, Phys. Rept. 512 (2012) 1.[2] K. Tsushima, A. Sibirtsev and A. W. Thomas, “Resonancemodel study of kaon production in baryon baryon reactionsfor heavy ion collisions”, Phys. Rev. C 59 (1999) 369.PHN-HSD-EXP-04 GSI SCIENTIFIC REPORT 201210

Constraining K$^{0}$ production channels in proton-proton collisions for transport  models

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Constraining K $^{0}$ production channels in proton-proton collisions for transport models

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Constraining K0^{0}0 production channels in proton-proton collisions for transport models

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Constraining K $^{0}$ production channels in proton-proton collisions for transport models