Abstract
The ALICE measurement of KS0 and Λ production at midrapidity in Pb-Pb collisions at sNN=2.76 TeV is presented. The transverse momentum (pT) spectra are shown for several collision centrality intervals and in the pT range from 0.4 GeV/c (0.6 GeV/c for Λ) to 12 GeV/c. The pT dependence of the Λ/KS0 ratios exhibits maxima in the vicinity of 3 GeV/c, and the positions of the maxima shift towards higher pT with increasing collision centrality. The magnitude of these maxima increases by almost a factor of three between most peripheral and most central Pb-Pb collisions. This baryon excess at intermediate pT is not observed in pp interactions at s=0.9 TeV and at s=7 TeV. Qualitatively, the baryon enhancement in heavy-ion collisions is expected from radial flow. However, the measured pT spectra above 2 GeV/c progressively decouple from hydrodynamical-model calculations. For higher values of pT, models that incorporate the influence of the medium on the fragmentation and hadronization processes describe qualitatively the pT dependence of the Λ/KS0 ratio.Received 29 July 2013DOI:https://doi.org/10.1103/PhysRevLett.111.222301This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.© 2013 CERN, for the ALICE Collaboration
Highlights
Collisions of heavy nuclei at ultrarelativistic energies are used to investigate a deconfined high temperature and density state of nuclear matter, the quark-gluon plasma. It was observed at the Relativistic Heavy Ion Collider (RHIC) [1,2], that the Ã=KS0 and p= ratios at intermediate presented. The transverse momentum (pT) (2–6 GeV=c) are markedly enhanced in central heavyion collisions when compared with peripheral or pp results
While at intermediate pT recombination might be dominating, hydrodynamical radial flow contributes to the baryon enhancement at lower pT, and fragmentation could take over at higher pT
The Ã=KS0 ratios observed in pp events at s 1⁄4 0:9 [11] and 7 TeV [20] agree within uncertainties over the presented pT range, and they bound in energy the Pb-Pb results reported here
Summary
The pT dependence of the Ã=KS0 ratios exhibits maxima in the vicinity of 3 GeV=c, and the positions of the maxima shift towards higher pT with increasing collision centrality. Ó 2013 CERN, for the ALICE Collaboration week ending 27 NOVEMBER 2013 between the specific energy loss (dE=dx) measured in the TPC and that defined by a momentum-dependent parametrization of the Bethe-Bloch curve was applied for the proton decay-product tracks.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
