Frankfurt am Main, Germany
Frankfurt am Main, Germany

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Anticic T.,Ruder Boskovic Institute | Baatar B.,Joint Institute for Nuclear Research | Barna D.,KFKI Research Institute | Bartke J.,Polish Academy of Sciences | And 73 more authors.
Physical Review C - Nuclear Physics | Year: 2011

The yields of (anti)protons were measured by the NA49 Collaboration in centrality-selected Pb+Pb collisions at 40A and 158A GeV. Particle identification was obtained in the laboratory momentum range from 5 to 63 GeV/c by measuring the energy loss dE/dx in the time projection chamber detector gas. The corresponding rapidity coverage extends 1.6 units from midrapidity into the forward hemisphere. Transverse-mass spectra, the rapidity dependences of the average transverse mass, and rapidity density distributions were studied as a function of collision centrality. The values of the average transverse mass as well as the midrapidity yields of protons normalized to the number of wounded nucleons show only modest centrality dependences. In contrast, the shape of the rapidity distribution changes significantly with collision centrality, especially at 40A GeV. The experimental results are compared to calculations of the hadron-string dynamics and the ultrarelativistic quantum-molecular-dynamics transport models. Super Prot. © 2011 The American Physical Society.


Anticic T.,Ruder Boskovic Institute | Baatar B.,Joint Institute for Nuclear Research | Barna D.,KFKI Research Institute | Bartke J.,Polish Academy of Sciences | And 70 more authors.
Physical Review C - Nuclear Physics | Year: 2011

Kaons and protons carry large parts of two conserved quantities: strangeness and baryon number. It is argued that their correlation and thus also fluctuations are sensitive to conditions prevailing at the anticipated parton-hadron phase boundary. Fluctuations of the (K++K -)/(p+p̄) and K+/p ratios have been measured for the first time by NA49 in central Pb+Pb collisions at five CERN Super Proton Synchrotron energies between √sNN=6.3 and √s NN=17.3 GeV. Both ratios exhibit a change of sign in σdyn, a measure of nonstatistical fluctuations, around √sNN=8 GeV. Below this energy, σdyn is positive, indicating higher fluctuation compared to a mixed event background sample, while for higher energies, σdyn is negative, indicating correlated emission of kaons and protons. The results are compared to hadronic transport model calculations which fail to reproduce the energy dependence. © 2011 American Physical Society.


Anticic T.,Ruder Boskovic Institute | Baatar B.,Joint Institute for Nuclear Research | Barna D.,KFKI Research Institute | Bartke J.,Polish Academy of Sciences | And 71 more authors.
Physical Review C - Nuclear Physics | Year: 2011

Production of the K *(892 )0 and K *(892 )0 resonances was studied via their K +π - and K -π + decay modes in central Pb+Pb, Si+Si, C+C, and inelastic p+p collisions at 158A GeV(√s NN=17.3 GeV) with the NA49 detector at the CERN SPS. Transverse momentum and rapidity distributions were measured and total yields were estimated. The yield of K * exceeds that of K * by about a factor of two in nucleus-nucleus reactions. The total yield ratios K */ + and * / - are strongly suppressed in central Pb+Pb compared to p+p, C+C, and Si+Si collisions, in agreement with the expected attenuation of these short-lived resonance states in the hadronic phase of the expanding fireball. The UrQMD model, although incorporating such a scenario, does not provide a quantitative description of the experimental results. The statistical hadron gas model assuming the same freeze-out parameters for stable hadrons and resonances overestimates the * / ratios in central Pb+Pb collisions by about a factor of 2.5. © 2011 American Physical Society.


Anticic T.,Ruder Boskovic Institute | Baatar B.,Joint Institute for Nuclear Research | Bartke J.,Polish Academy of Sciences | Beck H.,Fachbereich Physik der University | And 65 more authors.
Physical Review C - Nuclear Physics | Year: 2014

A novel approach, the identity method, was used for particle identification and the study of fluctuations of particle yield ratios in Pb + Pb collisions at the CERN Super Proton Synchrotron (SPS). This procedure allows one to measure the moments of the multiplicity distributions of protons (p), kaons (K), pions (π), and electrons (e) in case of incomplete particle identification. Using these moments the excitation function of the fluctuation measure νdyn[A,B] was measured, with A and B denoting different particle types. The obtained energy dependence of νdyn agrees with previously published NA49 results on the related measure σdyn. However, νdyn[K,p] and νdyn[K,π] were found to depend on the phase-space coverage. This feature most likely explains the reported differences between measurements of NA49 and those of STAR in central Au + Au collisions. © 2014 American Physical Society.


Anticic T.,Ruder Boskovic Institute | Baatar B.,Joint Institute for Nuclear Research | Barna D.,KFKI Research Institute | Bartke J.,Polish Academy of Sciences | And 69 more authors.
Physical Review C - Nuclear Physics | Year: 2012

Production of deuterons and antideuterons was studied by the NA49 experiment in the 23.5% most central Pb+Pb collisions at the top CERN Super Proton Synchroton (SPS) energy of √sN N=17.3 GeV. Invariant yields for d̄ and d were measured as a function of centrality in the center-of-mass rapidity range -1.2


Anticic T.,Ruder Boskovic Institute | Baatar B.,Joint Institute for Nuclear Research | Barna D.,Hungarian Academy of Sciences | Bartke J.,Polish Academy of Sciences | And 73 more authors.
Physical Review C - Nuclear Physics | Year: 2012

Measurements of charged pion and kaon production are presented in centrality selected Pb+Pb collisions at 40A GeV and 158A GeV beam energy as well as in semicentral C+C and Si+Si interactions at 40A GeV. Transverse mass spectra, rapidity spectra, and total yields are determined as a function of centrality. The system-size and centrality dependence of relative strangeness production in nucleus-nucleus collisions at 40A GeV and 158A GeV beam energy are derived from the data presented here and from published data for C+C and Si+Si collisions at 158A GeV beam energy. At both energies a steep increase with centrality is observed for small systems followed by a weak rise or even saturation for higher centralities. This behavior is compared to calculations using transport models (ultra-relativistic quantum molecular dynamics and hadron-string dynamics), a percolation model, and the core-corona approach. © 2012 American Physical Society.


Anticic T.,Ruder Boskovic Institute | Baatar B.,Joint Institute for Nuclear Research | Barna D.,KFKI Research Institute | Bartke J.,Polish Academy of Sciences | And 73 more authors.
Physical Review C - Nuclear Physics | Year: 2010

Pion production in nuclear collisions at the Super Proton Synchrotron (SPS) is investigated with the aim to search, in a restricted domain of the phase diagram, for power laws in the behavior of correlations that are compatible with critical QCD. We analyzed interactions of nuclei of different sizes (p+p, C+C, Si+Si, Pb+Pb) at 158A GeV adopting, as appropriate observables, scaled factorial moments in a search for intermittent fluctuations in transverse dimensions. The analysis is performed for π+π- pairs with an invariant mass very close to the two-pion threshold. In this sector one may capture critical fluctuations of the sigma component in a hadronic medium, even if the σ meson has no well-defined vacuum state. It turns out that for the Pb+Pb system the proposed analysis technique cannot be applied without entering the invariant mass region with strong Coulomb correlations. As a result the treatment becomes inconclusive in this case. Our results for the other systems indicate the presence of power-law fluctuations in the freeze-out state of Si+Si approaching in size the prediction of critical QCD. © 2010 The American Physical Society.


Anticic T.,Ruder Boskovic Institute | Baatar B.,Joint Institute for Nuclear Research | Bartke J.,Polish Academy of Sciences | Beck H.,Fachbereich Physik der University | And 68 more authors.
European Physical Journal C | Year: 2015

We look for fluctuations expected for the QCD critical point using an intermittency analysis in the transverse momentum phase space of protons produced around midrapidity in the 12.5 % most central C+C, Si+Si and Pb+Pb collisions at the maximum SPS energy of 158A GeV. We find evidence of power-law fluctuations for the Si+Si data. The fitted power-law exponent is consistent with the value expected for critical fluctuations. Power-law fluctuations had previously also been observed in low-mass collisions. © 2015, The Author(s).


Baatar B.,Joint Institute for Nuclear Research | Barr G.,University of Oxford | Bartke J.,Polish Academy of Sciences | Betev L.,CERN | And 21 more authors.
European Physical Journal C | Year: 2013

The production of protons, anti-protons, neutrons, deuterons and tritons in minimum bias p+C interactions is studied using a sample of 385 734 inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c beam momentum. The data cover a phase space area ranging from 0 to 1.9 GeV/c in transverse momentum and in Feynman x from -0.8 to 0.95 for protons, from -0.2 to 0.3 for anti-protons and from 0.1 to 0.95 for neutrons. Existing data in the far backward hemisphere are used to extend the coverage for protons and light nuclear fragments into the region of intra-nuclear cascading. The use of corresponding data sets obtained in hadron-proton collisions with the same detector allows for the detailed analysis and model-independent separation of the three principle components of hadronization in p+C interactions, namely projectile fragmentation, target fragmentation of participant nucleons and intra-nuclear cascading. © 2013 The Author(s).

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