Publications (111)78.91 Total impact
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Article: Critical fluctuations of the proton density in A+A collisions at $158A$ GeV
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ABSTRACT: Studies of QCD suggest the existence of a critical point in the phase diagram of strongly interacting matter. Close to this point, according to recent theoretical investigations, the net-proton density carries the critical fluctuations of the chiral order parameter. Using 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 158$A$ GeV we find evidence of power-law fluctuations for the Si+Si and Pb+Pb data. The fitted power-law exponent approaches the value expected for critical fluctuations. This suggests that the freeze-out states of these two systems are located in the phase diagram in the neighbourhood of the chiral critical point.08/2012; -
Article: Pion emission from the T2K replica target: method, results and application
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ABSTRACT: The T2K long-baseline neutrino oscillation experiment in Japan needs precise predictions of the initial neutrino flux. The highest precision can be reached based on detailed measurements of hadron emission from the same target as used by T2K exposed to a proton beam of the same kinetic energy of 30 GeV. The corresponding data were recorded in 2007-2010 by the NA61/SHINE experiment at the CERN SPS using a replica of the T2K graphite target. In this paper details of the experiment, data taking, data analysis method and results from the 2007 pilot run are presented. Furthermore, the application of the NA61/SHINE measurements to the predictions of the T2K initial neutrino flux is described and discussed.07/2012; -
Article: System-size and centrality dependence of charged kaon and pion production in nucleus-nucleus collisions at 40A GeV and158A GeV beam energy
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ABSTRACT: 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 semi-central 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 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 (UrQMD and HSD), a percolation model and the core-corona approach.07/2012; -
Article: Search for deconfinement in NA49 at the CERN SPS
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ABSTRACT: Experiment NA49 at the CERN SPS uses a large acceptance detector for a systematic study of particle yields and correlations in nucleus-nucleus, nucleon-nucleus and nucleon-nucleon collisions. Preliminary results for Pb+Pb collisions at 40, 80 and 158 A⋅GeV beam energy shown and compared to measurements at lower and higher energies.Pramana 04/2012; 60(4):725-737. · 0.57 Impact Factor -
Article: Antideuteron and deuteron production in midcentral Pb+Pb collisions at 158A GeV
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ABSTRACT: 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 √sNN=17.3 GeV. Invariant yields for d̅ and d were measured as a function of centrality in the center-of-mass rapidity range −1.2<y<−0.6. Results for d̅ (d) together with previously published p̅ (p) measurements are discussed in the context of the coalescence model. The coalescence parameters B2 were deduced as a function of transverse momentum pt and collision centrality.Phys. Rev. C. 04/2012; 85(4). -
Article: Inclusive J/psi production in pp collisions at sqrt(s) = 2.76 TeV
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ABSTRACT: The ALICE Collaboration has measured inclusive J/psi production in pp collisions at a center of mass energy sqrt(s)=2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ranges |y|<0.9 and 2.5<y<4 and have been obtained by measuring the electron and muon pair decay channels, respectively. The integrated luminosities for the two channels are L^e_int=1.1 nb^-1 and L^mu_int=19.9 nb^-1, and the corresponding signal statistics are N_J/psi^e+e-=59 +/- 14 and N_J/psi^mu+mu-=1364 +/- 53. We present dsigma_J/psi/dy for the two rapidity regions under study and, for the forward-y range, d^2sigma_J/psi/dydp_t in the transverse momentum domain 0<p_t<8 GeV/c. The results are compared with previously published results at sqrt(s)=7 TeV and with theoretical calculations.03/2012; -
Article: Suppression of high transverse momentum D mesons in central Pb--Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV
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ABSTRACT: The production of the prompt charm mesons $D^0$, $D^+$, $D^{*+}$, and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at the LHC, at a centre-of-mass energy $\sqrt{s_{NN}}=2.76$ TeV per nucleon--nucleon collision. The $\pt$-differential production yields in the range $2<p_t<16$ GeV/c at central rapidity, $|y|<0.5$, were used to calculate the nuclear modification factor $R_{AA}$ with respect to a proton-proton reference obtained from the cross section measured at $\sqrt{s}=7$ TeV and scaled to $\sqrt{s}=2.76$ TeV. For the three meson species, $R_{AA}$ shows a suppression by a factor 3-4, for transverse momenta larger than 5 GeV/c in the 20% most central collisions. The suppression is reduced for peripheral collisions.03/2012; -
Article: A search for ultra-high energy neutrinos in highly inclined events at the Pierre Auger Observatory
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ABSTRACT: The Surface Detector of the Pierre Auger Observatory is sensitive to neutrinos of all flavours above 0.1 EeV. These interact through charged and neutral currents in the atmosphere giving rise to extensive air showers. When interacting deeply in the atmosphere at nearly horizontal incidence, neutrinos can be distinguished from regular hadronic cosmic rays by the broad time structure of their shower signals in the water-Cherenkov detectors. In this paper we present for the first time an analysis based on down-going neutrinos. We describe the search procedure, the possible sources of background, the method to compute the exposure and the associated systematic uncertainties. No candidate neutrinos have been found in data collected from 1 January 2004 to 31 May 2010. Assuming an E^-2 differential energy spectrum the limit on the single flavour neutrino is (E^2 * dN/dE) < 1.74x10^-7 GeV cm^-2 s^-1 sr^-1 at 90% C.L. in the energy range 1x10^17 eV < E < 1x10^20 eV.02/2012; -
Article: Harmonic decomposition of two particle angular correlations in Pb-Pb collisions at root s(NN)=2.76 TeV
Physics Letters B 01/2012; 708(3-5):249-264. · 3.95 Impact Factor -
Article: Light vector meson production in pp collisions at root s=7 TeV ALICE Collaboration
Physics Letters B 01/2012; 710(4-5):557-568. · 3.95 Impact Factor -
Article: Measurement of electrons from semileptonic heavy-flavor hadron decays in pp collisions at root s=7 TeV
Physical Review D 01/2012; 86(11). · 4.56 Impact Factor -
Article: Inclusive J/psi production in pp collisions at root s=2.76 TeV
Physics Letters B 01/2012; 718(2):295-306. · 3.95 Impact Factor -
Article: (KsKs0)-K-0 correlations in pp collisions at root s=7 TeV from the LHC ALICE experiment
Physics Letters B 01/2012; 717(1-3):151-161. · 3.95 Impact Factor -
Article: Measurement of Production Properties of Positively Charged Kaons in Proton-Carbon Interactions at 31 GeV/c
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ABSTRACT: Spectra of positively charged kaons in p+C interactions at 31 GeV/c were measured with the NA61/SHINE spectrometer at the CERN SPS. The analysis is based on the full set of data collected in 2007 with a graphite target with a thickness of 4% of a nuclear interaction length. Interaction cross sections and charged pion spectra were already measured using the same set of data. These new measurements in combination with the published ones are required to improve predictions of the neutrino flux for the T2K long baseline neutrino oscillation experiment in Japan. In particular, the knowledge of kaon production is crucial for precisely predicting the intrinsic electron neutrino component and the high energy tail of the T2K beam. The results are presented as a function of laboratory momentum in 2 intervals of the laboratory polar angle covering the range from 20 up to 240 mrad. The kaon spectra are compared with predictions of several hadron production models. Using the published pion results and the new kaon data, the K+/\pi+ ratios are computed.12/2011; -
Article: Measurement of charm production at central rapidity in proton-proton collisions at sqrt(s) = 7 TeV
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ABSTRACT: The pt-differential inclusive production cross sections of the prompt charmed mesons D0, D+, and D*+ in the rapidity range |y|<0.5 were measured in proton-proton collisions at sqrt(s) = 7 TeV at the LHC using the ALICE detector. Reconstructing the decays D0->K-pi+, D+->K-pi+pi+, D*+->D0pi+, and their charge conjugates, about 8,400 D0, 2,900 D+, and 2,600 D*+ mesons with 1<pt<24 GeV/c were counted, after selection cuts, in a data sample of 3.14x10^8 events collected with a minimum-bias trigger (integrated luminosity L_int = 5/nb). The results are described within uncertainties by predictions based on perturbative QCD.11/2011; -
Article: J/psi polarization in pp collisions at sqrt(s)=7 TeV
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ABSTRACT: The ALICE Collaboration has studied J/psi production in pp collisions at sqrt(s)=7 TeV at the LHC through its muon pair decay. The polar and azimuthal angle distributions of the decay muons were measured, and results on the J/psi polarization parameters lambda_theta and lambda_phi were obtained. The study was performed in the kinematic region 2.5<y<4, 2<p_t<8 GeV/c, in the helicity and Collins-Soper reference frames. In both frames, the polarization parameters are compatible with zero, within uncertainties.11/2011; -
Article: Proton -- Lambda Correlations in Central Pb+Pb Collisions at sqrt(s_{NN}) = 17.3 GeV
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ABSTRACT: The momentum correlation between protons and lambda particles emitted from central Pb+Pb collisions at sqrt(s_{NN}) = 17.3 GeV was studied by the NA49 experiment at the CERN SPS. A clear enhancement is observed for small relative momenta (q_{inv} < 0.2 GeV). By fitting a theoretical model, which uses the strong interaction between the proton and the lambda in a given pair, to the measured data a value for the effective source size is deduced. Assuming a static Gaussian source distribution we derive an effective radius parameter of R_G = 3.02 \pm 0.20$(stat.)^{+0.44}_{-0.16}(syst.) fm.03/2011; -
Article: Measurements of Cross Sections and Charged Pion Spectra in Proton-Carbon Interactions at 31 GeV/c
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ABSTRACT: Interaction cross sections and charged pion spectra in p+C interactions at 31 GeV/c were measured with the large acceptance NA61/SHINE spectrometer at the CERN SPS. These data are required to improve predictions of the neutrino flux for the T2K long baseline neutrino oscillation experiment in Japan. A set of data collected during the first NA61/SHINE run in 2007 with an isotropic graphite target with a thickness of 4% of a nuclear interaction length was used for the analysis. The measured p+C inelastic and production cross sections are 257.2 +- 1.9 +- 8.9 mb and 229.3 +- 1.9 +- 9.0 mb, respectively. Inclusive production cross sections for negatively and positively charged pions are presented as a function of laboratory momentum in 10 intervals of the laboratory polar angle covering the range from 0 up to 420 mrad. The spectra are compared with predictions of several hadron production models.02/2011; -
Article: Energy dependence of kaon-to-proton ratio fluctuations in central Pb+Pb collisions from $\sqrt{s_{NN}}$ = 6.3 to 17.3 GeV
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ABSTRACT: 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 $(\mathrm{K}^+ + \mathrm{K}^-)/(\mathrm{p}+\bar{\mathrm{p}})$ and $\mathrm{K}^+/\mathrm{p}$ ratios have been measured for the first time by NA49 in central Pb+Pb collisions at 5 SPS energies between $\sqrt{s_{NN}}$= 6.3 GeV and 17.3 GeV. Both ratios exhibit a change of sign in $\sigma_{\mathrm{dyn}}$, a measure of non-statistical fluctuations, around $\sqrt{s_{NN}}$ = 8 GeV. Below this energy, $\sigma_{\mathrm{dyn}}$ is positive, indicating higher fluctuation compared to a mixed event background sample, while for higher energies, $\sigma_{\mathrm{dyn}}$ is negative, indicating correlated emission of kaons and protons. The results are compared to UrQMD calculations which which give a good description at the higher SPS energies, but fail to reproduce the transition to positive values.01/2011; -
Article: Two-pion Bose-Einstein correlations in central Pb-Pb collisions at root(NN)-N-S=2.76 TeV
Physics Letters B 01/2011; 696(4):328-337. · 3.95 Impact Factor
Top co-authors
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Institutions
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2001–2012
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Ruder Boskovic Institute
Zagreb, Grad Zagreb, Croatia -
Joint Institute for Nuclear Research
Dubna, Moskovskaya, Russia
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