Article

# Subthreshold kaon production and the nuclear equation of state

Cyclotron Institute and Physics Department, Texas A&M University, College Station, TX 77843, USA
(Impact Factor: 6.02). 11/1994; 349(4):405-410. DOI: 10.1016/0370-2693(95)00301-Z
Source: arXiv

ABSTRACT We reexamine in the relativistic transport model the dependence of kaon yield on the nuclear equation of state in heavy ion collisions at energies that are below the threshold for kaon production from the nucleon-nucleon interaction in free space. For Au+Au collisions at GeV/nucleon, we find that the kaon yield measured by the Kaos collaboration at GSI can be accounted for if a soft nuclear equation of state is used. We also confirm the results obtained in non-relativistic transport models that the dependence of kaon yield on the nuclear equation of state is more appreciable in heavy ion collisions at lower incident energies. We further clarify the difference between the predictions from the relativistic transport model and the non-relativistic transport model with a momentum-dependent potential.

0 Followers
·
130 Views
• Source
##### Article: Lambda hyperon production and polarization in collisions of p(3.5 GeV) + Nb
[Hide abstract]
ABSTRACT: 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 present versions of the employed models is able to fully reproduce the experimental distributions, i.e. in absolute yield and in shape. Presumably, this finding results from an insufficient modelling in the transport models of the elementary processes being relevant for $\Lambda$ production, rescattering and absorption. The present high-statistics data allow for a genuine two-dimensional investigation as a function of phase space of the self-analyzing $\Lambda$ polarization in the weak decay $\Lambda\rightarrow p \pi^-$. Finite negative values of the polarization in the order of $5-20\,\%$ are observed over the entire phase space studied. The absolute value of the polarization increases almost linearly with increasing transverse momentum for $p_t>300\,$MeV/c and increases with decreasing rapidity for $y < 0.8$.
European Physical Journal A 05/2014; 50(81). DOI:10.1140/epja/i2014-14081-2 · 2.42 Impact Factor
• Source
##### Article: On pp → pKΛ, NKΣ, ppϕ — the Basic Ingredients for Strangeness Production in Heavy Ion Collisions
[Hide abstract]
ABSTRACT: The strangeness production in heavy ion collisions was proposed to be probes of the nuclear equation of state, Kaon potential in nuclear medium, strange quark matter and quark-gluon plasma, etc. However, to act as reliable probes, proper understanding of the basic ingredients for the strangeness production, such as pp → pK+Λ, pp → ppϕ and pp → nK+Σ+ is necessary. Recent study of these reactions clearly shows that previously ignored contributions from the spin-parity 1/2- resonances, N*(1535) and Δ*(1620), are in fact very important for these reactions, especially for near-threshold energies. It is necessary to include these contributions for getting reliable calculation for the strangeness production in heavy ion collisions.
International Journal of Modern Physics E 10/2008; 17(09):1753-1764. DOI:10.1142/S0218301308010751 · 0.84 Impact Factor
• Source
##### Article: pp-->pK+Λ reaction in an effective Lagrangian model
[Hide abstract]
ABSTRACT: We investigate the pp-->pK+Λ reaction within an effective Lagrangian model where the contributions to the amplitudes are taken into account within the tree level. The initial interaction between the two nucleons is modeled by the exchange of π, ρ, ω, and σ mesons, and the ΛK+ production proceeds via the excitation of the N*(1650), N*(1710), and N*(1720) baryonic resonances. The parameters of the model at the nucleon-nucleon-meson vertices are determined by fitting the elastic nucleon-nucleon scattering with an effective interaction based on the exchange of these four mesons, while those at the resonance vertices are calculated from the known decay widths of the resonances as well as the vector meson dominance model. Available experimental data is described well by this approach. The one-pion-exchange diagram dominates the production process at both higher and lower beam energies. The ρ and ω meson exchanges make negligible contributions. However, the σ-exchange processes contribute substantially to the total cross sections at lower beam energies. The excitation of the N*(1710) and N*(1650) resonances dominate this reaction at beam momenta above and below 3 GeV/c, respectively. The interference among the amplitudes of various resonance excitation processes is significant. For beam energies very close to the K+ production threshold the hyperon-proton final state interaction effects are quite important. The data is selective about the model used to describe the low-energy scattering of the two final state baryons.
Physical Review C 11/1999; 60(5):55213-. DOI:10.1103/PhysRevC.60.055213 · 3.88 Impact Factor