C. Alt

Publications (71)31.46 Total impact

• Article: Energy dependence of particle ratio fluctuations in central Pb+Pb collisions from √sNN=6.3 to 17.3 GeV

  C. Alt, T. Anticic, B. Baatar, D. Barna, J. Bartke, L. Betev, H. Białkowska, C. Blume, B. Boimska, M. Botje, [......], P. Szymanski, V. Trubnikov, D. Varga, M. Vassiliou, G. I. Veres, G. Vesztergombi, D. Vranić, A. Wetzler, Z. Włodarczyk, I. K. Yoo
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  ABSTRACT: We present measurements of the energy dependence of event-by-event fluctuations in the K/π and (p+p̅ )/π multiplicity ratios in heavy-ion collisions at the CERN SPS. The particle ratio fluctuations were obtained for central Pb+Pb collisions at five collision energies, √sNN, between 6.3 and 17.3 GeV. After accounting for the effects of finite-number statistics and detector resolution, we extract the strength of nonstatistical fluctuations at each energy. For the K/π ratio, larger fluctuations than expected for independent particle production are found at all collision energies. The fluctuations in the (p+p̅ )/π ratio are smaller than expectations from independent particle production, indicating correlated pion and proton production from resonance decays. For both ratios, the deviation from purely statistical fluctuations shows an increase toward lower collision energies. The results are compared to transport model calculations, which fail to describe the energy dependence of the K/π ratio fluctuations.
  Phys. Rev. C. 04/2009; 79(4).
• Article: Energy dependence of ϕ meson production in central Pb+Pb collisions at √sNN=6 to 17 GeV

  C. Alt, T. Anticic, B. Baatar, D. Barna, J. Bartke, L. Betev, H. Białkowska, C. Blume, B. Boimska, M. Botje, [......], V. Trubnikov, D. Varga, M. Vassiliou, G. I. Veres, G. Vesztergombi, D. Vranić, A. Wetzler, Z. Włodarczyk, I. K. Yoo, J. Zimányi
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  ABSTRACT: ϕ meson production is studied by the NA49 Collaboration in central Pb+Pb collisions at 20A,30A,40A,80A, and 158A GeV beam energy. The data are compared with measurements at lower and higher energies and with microscopic and thermal models. The energy dependence of yields and spectral distributions is compatible with the assumption that partonic degrees of freedom set in at low SPS energies.
  Phys. Rev. C. 10/2008; 78(4).
• Article: Energy dependence of Λ and Ξ production in central Pb+Pb collisions at 20A,30A,40A,80A, and 158A GeV measured at the CERN Super Proton Synchrotron

  C. Alt, T. Anticic, B. Baatar, D. Barna, J. Bartke, L. Betev, H. Białkowska, C. Blume, B. Boimska, M. Botje, [......], D. Varga, M. Vassiliou, G. I. Veres, G. Vesztergombi, D. Vranić, A. Wetzler, Z. Włodarczyk, A. Wojtaszek, I. K. Yoo, J. Zimányi
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  ABSTRACT: Results on Λ,Λ̅ ,Ξ-, and Ξ̅ + production in central Pb+Pb reactions at 20A,30A,40A,80A, and 158A GeV are presented. The energy dependence of transverse mass spectra, rapidity spectra, and multiplicities is discussed. Comparisons to string hadronic models (UrQMD and HSD) and statistical hadron gas models are shown. Although the latter provide a reasonable description of all particle yields, the first class of models fails to match the Ξ- and Ξ̅ + multiplicities.
  Phys. Rev. C. 09/2008; 78(3).
• Source

  Available from: Predrag Buncic

  Article: Energy dependence of phi meson production in central Pb+Pb collisions at sqrt(s_nn) = 6 to 17 GeV

  C. Alt, T. Anticic, B Baatar, D Barna, J. Bartke, L Betev, H Bialkowska, C Blume, B Boimska, M Botje, [......], V Trubnikov, D Varga, M Vassiliou, G I Veres, G Vesztergombi, D Vranic, A. Wetzler, Z. Walodarczyk, I. K. Yoo, J. Zimanyi
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  ABSTRACT: Phi meson production is studied by the NA49 Collaboration in central Pb+Pb collisions at 20A, 30A, 40A, 80A and 158A GeV beam energy. The data are compared with measurements at lower and higher energies and to microscopic and thermal models. The energy dependence of yields and spectral distributions is compatible with the assumption that partonic degrees of freedom set in at low SPS energies.
  07/2008;
• Article: Bose-Einstein correlations of π-π- pairs in central Pb+Pb collisions at 20A,30A,40A,80A, and 158A GeV

  C. Alt, T. Anticic, B. Baatar, D. Barna, J. Bartke, L. Betev, H. Białkowska, C. Blume, B. Boimska, M. Botje, [......], D. Varga, M. Vassiliou, G. I. Veres, G. Vesztergombi, D. Vranić, A. Wetzler, Z. Włodarczyk, A. Wojtaszek, I. K. Yoo, J. Zimányi
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  ABSTRACT: Measurements of Bose-Einstein correlations of π-π- pairs in central Pb+Pb collisions were performed with the NA49 detector at the CERN Super Proton Synchroton for beam energies of 20A,30A,40A,80A, and 158A GeV. Correlation functions were measured in the longitudinally comoving “out-side-long” reference frame as a function of rapidity and transverse momentum in the forward hemisphere of the reaction. Radius and correlation strength parameters were obtained from fits of a Gaussian parametrization. The results show a decrease of the radius parameters with increasing transverse-momentum characteristic of strong radial flow in the pion source. No striking dependence on pion-pair rapidity or beam energy is observed. Static and dynamic properties of the pion source are obtained from simultaneous fits with a blast-wave model to radius parameters and midrapidity transverse-momentum spectra. Predictions of hydrodynamic and microscopic models of Pb+Pb collisions are discussed.
  Phys. Rev. C. 06/2008; 77(6).
• Source

  Available from: Roy Lacey

  Article: High transverse momentum hadron spectra at sqrt [s_ {NN}]= 17.3 GeV in Pb+ Pb and p+ p collisions

  C Alt, T Anticic, B Baatar, D Barna, J Bartke, L Betev, H Bia, C Blume, B Boimska, M Botje, [......], D Varga, M Vassiliou, G I Veres, G Vesztergombi, D Vrani, A Wetzler, Z W Lodarczyk, A Wojtaszek, I K Yoo, J Zimányi
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  ABSTRACT: Transverse momentum spectra up to 4.5 GeV/c around midrapidity of π ± , p, ¯ p, K ± in Pb+Pb reactions were measured at √ s N N = 17.3 GeV by the CERN-NA49 experiment. The nuclear mod-ification factors RAA for π ± and RCP for π ± , p, ¯ p, K ± were extracted and are compared to RHIC results at √ s N N = 200 GeV. The modification factor RAA shows a rapid increase with transverse momentum in the covered region. This indicates that the Cronin effect is the dominating effect in our energy range. The modification factor RCP , in which the contribution of the Cronin effect is reduced, shows a saturation well below unity in the π ± channel. The extracted RCP values follow the 200 GeV RHIC results closely in the available transverse momentum range, except for π ± above 2.5 GeV/c transverse momentum. There the measured suppression is smaller than that observed at RHIC.
  04/2008;
• Article: High transverse momentum hadron spectra at √sNN=17.3 GeV in Pb+Pb and p+p collisions

  C. Alt, T. Anticic, B. Baatar, D. Barna, J. Bartke, L. Betev, H. Białkowska, C. Blume, B. Boimska, M. Botje, [......], D. Varga, M. Vassiliou, G. I. Veres, G. Vesztergombi, D. Vranić, A. Wetzler, Z. Włodarczyk, A. Wojtaszek, I. K. Yoo, J. Zimányi
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  ABSTRACT: Transverse momentum spectra up to 4.5 GeV/c around midrapidity of π±,p,p̅ , and K± in Pb+Pb reactions were measured at √sNN=17.3 GeV by the CERN-NA49 experiment. The nuclear modification factors RAA for π± and RCP for π±,p,p̅ ,K± were extracted and compared with results obtained at the BNL Relativistic Heavy Ion Collider (RHIC) at √sNN=200 GeV. The modification factor RAA shows a rapid increase with transverse momentum in the covered region. This indicates that the Cronin effect is the dominating effect in our energy range. The modification factor RCP, in which the contribution of the Cronin effect is reduced, shows a saturation well below unity in the π± channel. The extracted RCP values follow the 200 GeV RHIC results closely in the available transverse momentum range, except for π± above 2.5 GeV/c transverse momentum. There the measured suppression is smaller than that observed at RHIC.
  Phys. Rev. C. 03/2008; 77(3).
• Article: Pion and kaon production in central Pb+Pb collisions at 20A and 30A GeV: Evidence for the onset of deconfinement

  C. Alt, T. Anticic, B. Baatar, D. Barna, J. Bartke, L. Betev, H. Białkowska, C. Blume, B. Boimska, M. Botje, [......], V. Trubnikov, D. Varga, M. Vassiliou, G. I. Veres, G. Vesztergombi, D. Vranić, A. Wetzler, Z. Włodarczyk, I. K. Yoo, J. Zimányi
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  ABSTRACT: Results on charged pion and kaon production in central Pb+Pb collisions at 20A and 30A GeV are presented and compared to data at lower and higher energies. Around 30A GeV a rapid change of the energy dependence for the yields of pions and kaons as well as for the shape of the transverse mass spectra is observed. The change is compatible with the prediction that the threshold for production of a state of deconfined matter at the early stage of the collisions is located at low CERN Super Proton Synchroton energies.
  Phys. Rev. C. 02/2008; 77(2).
• Source

  Available from: Roy Lacey

  Article: Event-by-event transverse momentum fluctuations in nuclear collisions at CERN SPS

  K Grebieszkow, C. Alt, T. Anticic, B Baatar, D Barna, J. Bartke, L Betev, H Białkowska, C Blume, B Boimska, [......], D Varga, M Vassiliou, G I Veres, G Vesztergombi, D Vranić, A. Wetzler, Z Włodarczyk, A Wojtaszek, I. K. Yoo, J Zimányi
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  ABSTRACT: The latest NA49 results on event-by-event transverse momentum fluctuations are presented for central Pb+Pb interactions over the whole SPS energy range (20A - 158A GeV). Two different methods are applied: evaluating the $\Phi_{p_{T}}$ fluctuation measure and studying two-particle transverse momentum correlations. The obtained results are compared to predictions of the UrQMD model. The results on the energy dependence are compared to the NA49 data on the system size dependence. The NA61 (SHINE, NA49-future) strategy of searching of the QCD critical end-point is also discussed.
  08/2007;
• Article: Rapidity and energy dependence of the electric charge correlations in A+A collisions from 20A to 158A GeV

  C. Alt, T. Anticic, B. Baatar, D. Barna, J. Bartke, L. Betev, H. Białkowska, C. Blume, B. Boimska, M. Botje, [......], D. Varga, M. Vassiliou, G. I. Veres, G. Vesztergombi, D. Vranić, A. Wetzler, Z. Włodarczyk, A. Wojtaszek, I. K. Yoo, J. Zimányi
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  ABSTRACT: Results from electric charge correlations studied with the Balance Function (BF) method in A+A collisions from 20A to 158A GeV are presented in two different rapidity intervals: In the midrapidity region we observe a decrease of the width of the BF distribution with increasing centrality of the collision, whereas this effect vanishes in the forward rapidity region. Results from the energy dependence study in central Pb+Pb collisions show that the narrowing of the BF expressed by the normalized width parameter W increases with energy toward the highest CERN Super Proton Synchrotron and BNL Relativistic Heavy Ion Collider energies. Finally we compare our experimental data points with the predictions of several models. The hadronic string models Ultra-relativistic Quantum Molecular Dynamics and Heavy Ion Jet INteraction Generator (HIJING) do not reproduce the observed narrowing of the BF. However, A MultiPhase Transport medel (AMPT), which contains a quark-parton transport phase before hadronization, can reproduce the narrowing of the BF's width with centrality. This confirms the proposed sensitivity of the BF analysis to the time of hadronization.
  Phys. Rev. C. 08/2007; 76(2).
• Article: Centrality and system size dependence of multiplicity fluctuations in nuclear collisions at 158A GeV

  C. Alt, T. Anticic, B. Baatar, D. Barna, J. Bartke, L. Betev, H. Białkowska, C. Blume, B. Boimska, M. Botje, [......], D. Varga, M. Vassiliou, G. I. Veres, G. Vesztergombi, D. Vranić, A. Wetzler, Z. Włodarczyk, A. Wojtaszek, I. K. Yoo, J. Zimńyi
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  ABSTRACT: The centrality and system size dependence of multiplicity fluctuations of charged particles produced in nuclear collisions at 158A GeV was studied by the NA49 Collaboration. Centrality selected Pb+Pb collisions, semicentral C+C and Si+Si collisions as well as inelastic p+p interactions were analyzed. The number of projectile participants determined on an event-by-event basis was used to characterize the collision centrality. The scaled variance of the multiplicity distribution obtained in the forward rapidity region (1.1<yc.m.<2.6) shows a significant increase toward peripheral collisions. The results are similar for negatively and positively charged particles and about 50% larger for all charged particles. String-hadronic models of nuclear reactions without the fusion process do not reproduce the rise of fluctuations from central toward peripheral collisions. The measured centrality dependence can be reproduced in superposition models with the assumption of contributions from target participants to particle production in the forward hemisphere or in string models with fusion.
  Phys. Rev. C. 06/2007; 75(6).
• Article: Inclusive production of charged pions in p + C collisions at 158 GeV/c beam momentum

  C. Alt, B. Baatar, D. Barna, G. Barr, J. Bartke, L. Betev, H. Białkowska, C. Blume, B. Boimska, J. Bracinik, [......], V. Trubnikov, D. Varga, M. Vassiliou, G.I. Veres, G. Vesztergombi, D. Vranić, S. Wenig, A. Wetzler, J. Zaranek, The NA Collaboration
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  ABSTRACT: The production of charged pions in minimum bias p+C interactions is studied using a sample of 377000 inelastic events obtained with the NA49 detector at the CERN SPS at 158GeV/c beam momentum. The data cover a phase space area ranging from 0 to 1.8GeV/c in transverse momentum and from -0.1 to 0.5 in Feynman xF. Inclusive invariant cross sections are given on a grid of 270 bins per charge, thus offering for the first time a dense coverage of the projectile hemisphere and of the cross-over region into the target fragmentation zone.
  European Physical Journal C 02/2007; 49(4):897-917. · 3.63 Impact Factor
• Article: NA49 Collaboration

  C. Alt, T. Anticic, B. Baatar, D. Barna, J. Bartke, L. Betev, H. Białkowska, C. Blume, B. Boimska, M. Botje, [......], V. Trubnikov, D. Varga, M. Vassiliou, G. I. Veres, G. Vesztergombi, D. Vranić, A. Wetzler, Z. Włodarczyk, I. K. Yoo, J. Zimányi
  Nuclear Physics A 07/2006; 774:943-944. · 1.54 Impact Factor
• Article: Energy and centrality dependence of p̅ and p production and the Λ̅ /p̅ ratio in Pb+Pb collisions between 20A GeV and 158A GeV

  C. Alt, T. Anticic, B. Baatar, D. Barna, J. Bartke, L. Betev, H. Białkowska, C. Blume, B. Boimska, M. Botje, [......], V. Trubnikov, D. Varga, M. Vassiliou, G. I. Veres, G. Vesztergombi, D. Vranić, A. Wetzler, Z. Włodarczyk, I. K. Yoo, J. Zimányi
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  ABSTRACT: The transverse mass mt 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 〈mt〉 derived from the mt 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 mt distributions of p̅ and p are very similar. The ratios of the particle yields, p̅ /p and Λ̅ /p̅ , are also analyzed. The p̅ /p ratio exhibits an increase with decreasing centrality and a steep rise with increasing beam energy. The Λ̅ /p̅ ratio increases beyond unity with decreasing beam energy.
  Phys. Rev. C. 04/2006; 73(4).
• Article: Upper limit of D0 production in central Pb-Pb collisions at 158A GeV

  C. Alt, T. Anticic, B. Baatar, D. Barna, J. Bartke, L. Betev, H. Białkowska, C. Blume, B. Boimska, M. Botje, [......], V. Trubnikov, D. Varga, M. Vassiliou, G. I. Veres, G. Vesztergombi, D. Vranić, A. Wetzler, Z. Włodarczyk, I. K. Yoo, J. Zimányi
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  ABSTRACT: Results are presented from a search for the decays D0→K-π+ and D̅ 0→K+π- in a sample of 3.8×106 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 D0 production is derived and compared to predictions from several models.
  Phys. Rev. C. 03/2006; 73(3).
• Source

  Available from: Zbigniew Włodarczyk

  Article: Omega- and Omega+ production in central Pb + Pb collisions at 40 and 158A GeV.

  C Alt, T Anticic, B Baatar, D Barna, J Bartke, L Betev, H Białkowska, A Billmeier, C Blume, B Boimska, [......], D Varga, M Vassiliou, G I Veres, G Vesztergombi, D Vranić, A Wetzler, Z Włodarczyk, I K Yoo, J Zaranek, J Zimányi
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  ABSTRACT: Results are presented on Omega production in central Pb+Pb collisions at 40 and 158A GeV beam energy. For the first time in heavy ion reactions, rapidity distributions and total yields were measured for the sum Omega(-) + Omega(+) at 40A GeV and for Omega(-) and Omega(+) separately at 158A GeV. The yields are strongly underpredicted by the string-hadronic UrQMD model but agree better with predictions from hadron gas models.
  Physical Review Letters 06/2005; 94(19):192301. · 7.37 Impact Factor
• Article: System size and centrality dependence of the balance function in A+A collisions at √sNN=17.2 GeV

  C. Alt, T. Anticic, B. Baatar, D. Barna, J. Bartke, L. Betev, H. Białkowska, A. Billmeier, C. Blume, B. Boimska, [......], D. Varga, M. Vassiliou, G. I. Veres, G. Vesztergombi, D. Vranić, A. Wetzler, Z. Włodarczyk, I. K. Yoo, J. Zaranek, J. Zimányi
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  ABSTRACT: Electric charge correlations were studied for p+p, C+C, Si+Si, and centrality selected Pb+Pb collisions at √sNN=17.2 GeV with the NA49 large acceptance detector at the CERN SPS. In particular, long-range pseudorapidity correlations of oppositely charged particles were measured using the balance function method. The width of the balance function decreases with increasing system size and centrality of the reactions. This decrease could be related to an increasing delay of hadronization in central Pb+Pb collisions.
  Phys. Rev. C. 03/2005; 71(3).
• Source

  Available from: Zbigniew Włodarczyk

  Article: System-size dependence of strangeness production in nucleus-nucleus collisions at squareroot[sNN]=17.3 GeV.

  C Alt, T Anticic, B Baatar, D Barna, J Bartke, L Betev, H Białkowska, A Billmeier, C Blume, B Boimska, [......], D Varga, M Vassiliou, G I Veres, G Vesztergombi, D Vranić, A Wetzler, Z Włodarczyk, I K Yoo, J Zaranek, J Zimányi
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  ABSTRACT: Emission of pi+/-, K+/-, phi, and Lambda was measured in near-central C+C and Si+Si collisions at 158 AGeV beam energy. Together with earlier data for p+p, S+S, and Pb+Pb, the system-size dependence of relative strangeness production in nucleus-nucleus collisions is obtained. Its fast rise and the saturation observed at about 60 participating nucleons can be understood as the onset of the formation of coherent systems of increasing size.
  Physical Review Letters 03/2005; 94(5):052301. · 7.37 Impact Factor
• Article: Multiplicity fluctuations in nuclear collisions at 158A GeV

  Maciej Rybczyński, C Alt, T Anticic, B Baatar, D Barna, J Bartke, L Betev, H Białkowska, A Billmeier, C Blume, [......], D Varga, M Vassiliou, G I Veres, G Vesztergombi, D Vranić, A Wetzler, Z Włodarczyk, I K Yoo, J Zaranek, J Zimányi
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  ABSTRACT: The system size dependence of multiplicity fluctuations of charged particles produced in nuclear collisions at 158 A GeV was studied in the NA49 CERN experiment. The results indicate a non-monotonic dependence of the scaled variance of the multiplicity distribution with a maximum for semi-peripheral Pb+Pb interactions with number of projectile participants of about 35. This effect is not observed in a string-hadronic model of nuclear collision HIJING.
  Journal of Physics Conference Series 02/2005; 5(1):74.
• Article: Electric charge fluctuations in central Pb+Pb collisions at 20A, 30A, 40A, 80A, and 158A GeV

  C. Alt, T. Anticic, B. Baatar, D. Barna, J. Bartke, M. Behler, L. Betev, H. Białkowska, A. Billmeier, C. Blume, [......], D. Varga, M. Vassiliou, G. I. Veres, G. Vesztergombi, D. Vranic, A. Wetzler, Z. Włodarczyk, I. K. Yoo, J. Zaranek, J. Zimányi
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  ABSTRACT: Results are presented on event-by-event electric charge fluctuations in central Pb+Pb collisions at 20A,30A,40A,80A, and 158A GeV. The observed fluctuations are close to those expected for a gas of pions correlated by global charge conservation only. These fluctuations are considerably larger than those calculated for an ideal gas of deconfined quarks and gluons. The present measurements do not necessarily exclude reduced fluctuations from a quark-gluon plasma because these might be masked by contributions from resonance decays.
  Phys. Rev. C. 12/2004; 70(6).