Erratum: Observation of D0 meson nuclear modifications in Au+Au collisions at sNN =200 GeV (Physical Review Letters (2014) 113 (142301) DOI: 10.1103/PhysRevLett.113.142301)

STAR Collaboration

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In this Erratum we report changes on the D0 pT spectra and nuclear modification factor ( RAA) in Au+Au collisions at σsNN=200GeV by fixing the errors in the efficiency and selection criteria that affected the Au+Au results. The p+p reference spectrum has changed as well and is updated with new fragmentation parameters. In this Letter, we reported on measurements of the nuclear modification factor of D0 mesons in Au+Au collisions at σsNN=200GeV. We have identified two errors in the estimation of the particle identification efficiency. Considering the high combinatorial background in D0 meson reconstruction in Au+Au collisions, a hybrid particle identification method was used in this analysis to improve significance of the signal. For p<1.6GeV/c, pion and kaon candidates were selected by requiring a selection on the ionization energy loss of the particle passing through the Time Projection Chamber (TPC), good matching to a hit on the Time of Flight detector (TOF), and a TOF 1/β (the reciprocal of particle velocity) selection. For p>1.6GeV/c, candidates were required to pass the TPC ionization energy loss (dE/dx) selection and the 1/β selection was required for those tracks with good TOF matching. This helps to enhance pion and kaon identification purity. The first error was that in the analysis of the reconstructed data, we did not correctly reject tracks with TOF matching, but with no valid β information due to unavailable calibration parameters. The second error was that we accounted for the efficiency of a distance of closest approach to primary vertex (DCA) selection twice. The DCA-in-the-transverse-plane selection was applied to tracks to insure a good TOF path length calculation by ensuring the tracks are primary. The difference in efficiency from the two errors combined is 30% for single tracks at low pT and it decreases with increasing pT compared with the previous result in Au+Au collisions. This results in a factor of 2 higher D0 yields estimation at pT<2GeV/ccompared to the case when the correct algorithm is used, affecting results in all centralities in this Letter.After correcting the two errors, the new D0 pT spectra are shown in Fig. 2 as solid symbols for different centrality bins. The vertical bars on the points represent the statistical uncertainties and the brackets denote the systematic uncertainties. The measured D0 production cross section per nucleon-nucleon-collision at midrapidity in the 0%-10% most-central collisions is updated as 41±4(stat)±5(syst)μb. The p+p D0 reference spectrum, shown as open circles, was obtained using the D0 measurement at pT<2.0GeV/c and D∗± measurement at pT>2.0GeV/c. We updated our p+p reference spectrum in this Erratum using the latest global analysis of charm fragmentation ratios from Ref. [2] and also by taking into account the pT dependence of the fragmentation ratio between D0 and D∗± from pythia 6.4 [3], which increases the yield as pT increases, reaching 40%. The dashed curves are Levy function [4] fits to the p+p reference, scaled by the number of binary collisions, Nbin [5]. In our previous p+p collision analysis, TOF matching was always required for the entire pT region in order to minimize the pileup impact in high luminosity p+p collisions. Therefore, the p+p data were not affected by the error in the Au+Au analysis due to a less complicated algorithm. With these new updates, the p+p D0 production cross section at midrapidity is measured as 80±11(stat)±16(syst)μb. (Figure Presented).

Original languageEnglish (US)
Article number229901
JournalPhysical Review Letters
Issue number22
StatePublished - Nov 28 2018

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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