System size dependence of strange particle yields and spectra at sqrt(s)=17.3 GeV

Yields and spectra of strange hadrons (K+, K-, phi, Lambda and Antilambda) as well as of charged pions were measured in near central C+C and Si+Si collisions at 158 AGeV beam energy with the NA49 detector. Together with earlier data for p+p, S+S and Pb+Pb reactions the system size dependence can be studied. Relative strangeness production rises fast and saturates at about 60 participating nucleons; the net hyperon spectra show an increasing shift towards midrapidity for larger colliding nuclei. An interpretation based on the formation of coherent systems of increasing volume is proposed. The transverse mass spectra can be described by a blast wave ansatz. Increasing flow velocity is accompanied by decreasing temperatures for both kinetic and chemical freeze out. The increasing gap between inelastic and elastic decoupling leaves space for rescattering.Comment: 8 pages, 6 figures, Proceedings of the Hot Quarks 2004 worksho

Measurement of negatively charged pion spectra in inelastic p plus p interactions at p(lab)=20, 31, 40, 80 and 158 GeV/c

We present experimental results on inclusive spectra and mean multiplicities of negatively charged pions produced in inelastic p+p interactions at incident projectile momenta of 20, 31, 40, 80 and 158 GeV/c ($\sqrt{s} =$ 6.3, 7.7, 8.8, 12.3 and 17.3 GeV, respectively). The measurements were performed using the large acceptance NA61/SHINE hadron spectrometer at the CERN Super Proton Synchrotron. Two-dimensional spectra are determined in terms of rapidity and transverse momentum. Their properties such as the width of rapidity distributions and the inverse slope parameter of transverse mass spectra are extracted and their collision energy dependences are presented. The results on inelastic p+p interactions are compared with the corresponding data on central Pb+Pb collisions measured by the NA49 experiment at the CERN SPS. The results presented in this paper are part of the NA61/SHINE ion program devoted to the study of the properties of the onset of deconfinement and search for the critical point of strongly interacting matter. They are required for interpretation of results on nucleus-nucleus and proton-nucleus collisions

Energy and centrality dependence of (p)over-bar and p production and the (Lambda)over-bar/(p)over-bar ratio in Pb plus Pb collisions between 20A GeV and 158A GeV

The transverse mass m(t) distributions for antiprotons are measured at midrapidity for minimum bias Pb+Pb collisions at 158A GeV and for central Pb+Pb collisions at 20A, 30A, 40A, and 80A GeV beam energies in the fixed target experiment NA49 at the CERN SPS. The rapidity density dn/dy, inverse slope parameter T, and mean transverse mass < m(t)> derived from the m(t) distributions are studied as a function of the incident energy and the collision centrality and compared to the relevant data on proton production. The shapes of the m(t) distributions of (p) over bar and p are very similar. The ratios of the particle yields, (p) over bar /p and (p) over bar/(Lambda) over bar, are also analyzed. The (p) over bar /p ratio exhibits an increase with decreasing centrality and a steep rise with increasing beam energy. The (Lambda) over bar/(Lambda) over bar ratio increases beyond unity with decreasing beam energy

Hadronic expansion dynamics in central Pb+Pb collisions at 158 GeV per nucleon

Two-particle correlation functions of negative hadrons over wide phase space, and transverse mass spectra of negative hadrons and deuterons near mid-rapidity have been measured in central Pb+Pb collisions at 158 GeV per nucleon by the NA49 experiment at the CERN SPS. A novel Coulomb correction procedure for the negative two-particle correlations is employed making use of the measured oppositely charged particle correlation. Within an expanding source scenario these results are used to extract the dynamic characteristics of the hadronic source, resolving the ambiguities between the temperature and transverse expansion velocity of the source, that are unavoidable when single and two particle spectra are analysed separately. The source shape, the total duration of the source expansion, the duration of particle emission, the freeze-out temperature and the longitudinal and transverse expansion velocities are deduced

Upper limit of D-0 production in central Pb-Pb collisions at 158A GeV

Results are presented from a search for the decays D-0-> K(-)pi(+) and (D) over bar (0)-> K(+)pi(-) in a sample of 3.8x10(6) central Pb-Pb events collected with a beam energy of 158A GeV by NA49 at the CERN SPS. No signal is observed. An upper limit on D-0 production is derived and compared to predictions from several models

Measurements of production properties of K S 0 mesons and Λ hyperons in proton-carbon interactions at 31 GeV/ c

Spectra of KS0 mesons and Λ hyperons were measured in p + C interactions at 31 GeV/c with the large acceptance NA61/SHINE spectrometer at the CERN SPS. The data were collected with an isotropic graphite target with a thickness of 4% of a nuclear interaction length. Interaction cross sections, charged pion spectra, and charged kaon spectra were previously measured using the same data set. Results on KS0 and Λ production in p + C interactions serve as a reference for the understanding of the enhancement of strangeness production in nucleus-nucleus collisions. Moreover, they provide important input for the improvement of neutrino flux predictions for the T2K long baseline neutrino oscillation experiment in Japan. Inclusive production cross sections for KS0 and Λ are presented as a function of laboratory momentum in intervals of the laboratory polar angle covering the range from 0 up to 240 mrad. The results are compared with predictions of several hadron production models. The KS0 mean multiplicity in production processes 〈nKS0〉 and the inclusive cross section for KS0 production σKS0 were measured and amount to 0.127 ± 0.005 (stat) ± 0.022 (sys) and 29.0 ± 1.6 (stat) ± 5.0 (sys) mb, respectively. © 2014 American Physical Society

Measurements of production properties of K S 0 mesons and Λ hyperons in proton-carbon interactions at 31 GeV/ c

Spectra of KS0 mesons and Λ hyperons were measured in p + C interactions at 31 GeV/c with the large acceptance NA61/SHINE spectrometer at the CERN SPS. The data were collected with an isotropic graphite target with a thickness of 4% of a nuclear interaction length. Interaction cross sections, charged pion spectra, and charged kaon spectra were previously measured using the same data set. Results on KS0 and Λ production in p + C interactions serve as a reference for the understanding of the enhancement of strangeness production in nucleus-nucleus collisions. Moreover, they provide important input for the improvement of neutrino flux predictions for the T2K long baseline neutrino oscillation experiment in Japan. Inclusive production cross sections for KS0 and Λ are presented as a function of laboratory momentum in intervals of the laboratory polar angle covering the range from 0 up to 240 mrad. The results are compared with predictions of several hadron production models. The KS0 mean multiplicity in production processes 〈nKS0〉 and the inclusive cross section for KS0 production σKS0 were measured and amount to 0.127 ± 0.005 (stat) ± 0.022 (sys) and 29.0 ± 1.6 (stat) ± 5.0 (sys) mb, respectively. © 2014 American Physical Society