Long-range angular correlations of π, K and p in p-Pb collisions at √{sNN}=5.02 TeV
Abstract
Angular correlations between unidentified charged trigger particles and various species of charged associated particles (unidentified particles, pions, kaons, protons and antiprotons) are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV in the transverse-momentum range 0.3<pT<4 GeV/c. The correlations expressed as associated yield per trigger particle are obtained in the pseudorapidity range |ηlab|<0.8. Fourier coefficients are extracted from the long-range correlations projected onto the azimuthal angle difference and studied as a function of pT and in intervals of event multiplicity. In high-multiplicity events, the second-order coefficient for protons, v2p, is observed to be smaller than that for pions, v2π, up to about pT=2 GeV/c. To reduce correlations due to jets, the per-trigger yield measured in low-multiplicity events is subtracted from that in high-multiplicity events. A two-ridge structure is obtained for all particle species. The Fourier decomposition of this structure shows that the second-order coefficients for pions and kaons are similar. The v2p is found to be smaller at low pT and larger at higher pT than v2π, with a crossing occurring at about 2 GeV/c. This is qualitatively similar to the elliptic-flow pattern observed in heavy-ion collisions. A mass ordering effect at low transverse momenta is consistent with expectations from hydrodynamic model calculations assuming a collectively expanding system.
- Publication:
-
Physics Letters B
- Pub Date:
- October 2013
- DOI:
- 10.1016/j.physletb.2013.08.024
- arXiv:
- arXiv:1307.3237
- Bibcode:
- 2013PhLB..726..164A
- Keywords:
-
- Nuclear Experiment;
- High Energy Physics - Experiment
- E-Print:
- 26 pages, 4 captioned figures, 2 tables, authors from page 20, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/445