Strange particle production from SIS to LHC

Journal of Physics G: Nuclear and Particle Physics, 2003

The production and the propagation of K +-and of K −-mesons in heavyion collisions at beam energies of 1 to 2 AGeV have systematically been investigated with the Kaon Spectrometer KaoS at the SIS at the GSI. The ratio of the K +production excitation function for Au+Au and for C+C reactions increases with decreasing beam energy, which is expected for a soft nuclear equation-of-state. At 1.5 AGeV a comprehensive study of the K +-and of the K −-emission as a function of the size of the collision system, of the collision centrality, of the kaon energy, and of the polar emission angle has been performed. The K − /K + ratio is found to be nearly constant as a function of the collision centrality. The spectral slopes and the polar emission patterns are different for K − and for K +. These observations indicate that K +-mesons decouple earlier from the reaction zone than K −-mesons.

2004

Production of the doubly strange Ξ baryon in heavy-ion collisions at SIS energies is studied in a relativistic transport model that includes perturbatively the strangeness-exchange reactions KΛ → πΞ andKΣ → πΞ. Taking the cross sections for these reactions from the predictions of a hadronic model, we find that the Ξ yield is about 10 −4 in central collisions of 58 Ni + 58 Ni at E/A = 1.93 GeV. The Ξ yield is further found to be more sensitive to the magnitude of the cross sections for strangeness-exchange reactions than to the medium effects due to modified kaon properties. We have also made predictions for Ξ production in Au+Au collisions at energies from 1 to 2 GeV/nucleon.

Pramana, 2006

In these lectures we discuss the investigation of the strange meson production in protonproton (pp) and in proton-nucleus (pA) reactions within an effective Lagrangian model. The kaon production proceeds mainly via the excitations of N * (1650), N * (1710), and N * (1720) resonant intermediate nucleonic states, in the collision of two initial state nucleons. Therefore, the strangeness production is expected to provide information about the resonances lying at higher excitation energies. For beam energies very close to the kaon production threshold the hyperon-proton final state interaction effects are quite important. Thus, these studies provide a check on the models of hyperon-nucleon interactions. The inmedium production of kaons show strong sensitivity to the self energies of the intermediate mesons.

International Journal of Modern Physics E, 2009

Strange meson production reactions are expected to provide information on the manifestation of quantum chromodynamics in the non-perturbative regime of energies larger than that of the low energy pion physics. The K meson contains a strange quark (s) or antiquark [Formula: see text] while the η meson has hidden strangeness as it contains some component of the [Formula: see text] pair. In this lecture we present an overview of describing the production of K and η mesons in nucleon-nucleon collisions within an effective Lagrangian model (ELM) where meson production proceeds via excitation, propagation and subsequent decay of intermediate baryonic resonant states. Specific examples are discussed where proper understanding of the data is still lacking.

Physical Review D, 2013

Measurements are presented of the production of primary K 0 S and à particles in proton-proton collisions at ffiffi ffi s p ¼ 7 TeV in the region transverse to the leading charged-particle jet in each event. The average multiplicity and average scalar transverse momentum sum of K 0 S and à particles measured at pseudorapidities jj < 2 rise with increasing charged-particle jet p T in the range 1-10 GeV=c and saturate in the region 10-50 GeV=c. The rise and saturation of the strange-particle yields and transverse momentum sums in the underlying event are similar to those observed for inclusive charged particles, which confirms the impact-parameter picture of multiple parton interactions. The results are compared to recent tunes of the PYTHIA Monte Carlo event generator. The PYTHIA simulations underestimate the data by 15%-30% for K 0 S mesons and by about 50% for à baryons, a deficit similar to that observed for the inclusive strange-particle production in non-single-diffractive proton-proton collisions. The constant strange-to charged-particle activity ratios with respect to the leading jet p T and similar trends for mesons and baryons indicate that the multiparton-interaction dynamics is decoupled from parton hadronization, which occurs at a later stage.

Nuclear Physics A, 2003

Exclusive data on the reactions pp → ppK + K − and pp → pK + Λ/Σ 0 have been taken at the cooler synchrotron COSY close to threshold.

2004

We investigate the associated strangeness Lambda K+ and Sigma0 K+ productions in proton-proton collisions within an effective Lagrangian model. The initial interaction between the two nucleons is modeled by the exchange of pi, rho, omega, and sigma mesons and the strangeness production proceeds via excitations of 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 and from the vector meson dominance model. Experimental data taken recently by the COSY-11 collaboration are described well by this approach. The one-pion-exchange diagram dominates the production process at both higher and lower beam energies. The excitation of the N*(1650) resonance dominates both the production channels...

European Physical Journal C, 1990

The production of Λ, $\bar \Lambda$ andK s 0 has been studied in 200 GeV/nucleonp+S and S+S collisions in the streamer chamber of the NA35 experiment at the CERN SPS. Significant enhancement of the multiplicities of all observed strange particles relative to negative hadrons was observed in central S+S collisions, as compared top+p andp+S collisions. The latter collisions show no overall (relative) strangeness enhancement overp+p, but the rapidity distributions and hadron multiplicities indicate some secondary cascading production of Λ particles in thep+S andp+Au collisions. The Λ polarization in central S+S collisions was found to be compatible with zero up top T =2 GeV/c.

Journal of Physics G: Nuclear and Particle Physics, 2002

The production of K + and K − mesons in elementary proton-proton collision has been investigated at the Cooler Synchrotron COSY in Jülich. A high quality proton beam with low emittance and small momentum spread permitted to study the creation of these mesons very close to the kinematical threshold.

Zeitschrift für Physik C: Particles and Fields, 1989

The production of neutral strange particles K ~ A and A has been studied in 60 and 200 GeV per nucleon OAu and pAu collisions with the streamer chamber vertex spectrometer of the NA35 experiment at the CERN-SPS accelerator. Ratios of neutral strange particle production to negatively charged particle production in selected regions of phase space were measured to be the same in OAu and pAu reactions. The rates of strange particle production in central OAu collisions are about a factor of 16 higher than in pAu collisions when compared in the same regions of phase space. If an enhancement of strange particle production in OAu collisions relative to pAu collisions is considered to be a signature for quark-gluon plasma formation, no evidence sup-