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Title: Elliptic flow of charged pions, protons and strange particles emitted in Pb+Au collisions at top SPS energy

Abstract

Differential elliptic flow spectra v 2(p T) of π -, K$$0\atop{2}$$, p, Λ have been measured at √s NN around midrapidity by the CERN-CERES/NA45 experiment in mid-central Pb + Au collisions (10% of σ geo). The pT range extends from about 0.1 GeV/c (0.55 GeV/c for Λ) to more than 2 GeV/c. Protons below 0.4 GeV/c are directly identified by dE/dx. At higher pT, proton elliptic flow is derived as a constituent, besides π + and K +, of the elliptic flow of positive pion candidates. This retrieval requires additional inputs: (i) of the particle composition, and (ii) of v 2(p T) of positive pions. For (i), particle ratios obtained by NA49 are adapted to CERES conditions; for (ii), the measured v 2(p T) of negative pions is substituted, assuming π + and π - elliptic flow magnitudes to be sufficiently close. The v 2(p T) spectra are compared to ideal-hydrodynamics calculations. In synopsis of the series π -, K$$0\atop{2}$$-p-Λ, flow magnitudes are seen to fall with decreasing pT progressively even below hydro calculations with early kinetic freeze-out (T f=160 MeV) leaving not much time for hadronic evolution. The proton v 2(p T) data show a downward swing towards low p T with excursions into negative v 2 values. The pion-flow isospin asymmetry observed recently by STAR at RHIC, invalidating in principle our working assumption, is found in its impact on proton flow bracketed from above by the direct proton flow data, and not to alter any of our conclusions. Results are discussed in perspective of recent viscous hydrodynamics studies which focus on late hadronic stages.

Authors:
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Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1079299
Report Number(s):
BNL-98931-2012-JA
Journal ID: ISSN 0375-9474; KA-04
DOE Contract Number:  
AC02-98CH10886
Resource Type:
Journal Article
Journal Name:
Nuclear Physics. A
Additional Journal Information:
Journal Volume: 894; Journal Issue: C; Journal ID: ISSN 0375-9474
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; flow; strangeness; viscosity

Citation Formats

Adamová, D., Agakichiev, G., Andronic, A., Antończyk, D., Appelshäuser, H., Belaga, V., Bielčíková, J., Braun-Munzinger, P., Busch, O., Cherlin, A., Damjanović, S., Dietel, T., Dietrich, L., Drees, A., Dubitzky, W., Esumi, S. I., Filimonov, K., Fomenko, K., Fraenkel, Z., Garabatos, C., Glässel, P., Hering, G., Holeczek, J., Kalisky, M., Krobath, G., Kushpil, V., Maas, A., Marín, A., Milošević, J., Miśkowiec, D., Panebrattsev, Y., Petchenova, O., Petráček, V., Radomski, S., Rak, J., Ravinovich, I., Rehak, P., Sako, H., Schmitz, W., Schuchmann, S., Sedykh, S., Shimansky, S., Stachel, J., Šumbera, M., Tilsner, H., Tserruya, I., Tsiledakis, G., Wessels, J. P., Wienold, T., Wurm, J. P., Yurevich, S., and Yurevich, V. Elliptic flow of charged pions, protons and strange particles emitted in Pb+Au collisions at top SPS energy. United States: N. p., 2012. Web. doi:10.1016/j.nuclphysa.2012.08.004.
Adamová, D., Agakichiev, G., Andronic, A., Antończyk, D., Appelshäuser, H., Belaga, V., Bielčíková, J., Braun-Munzinger, P., Busch, O., Cherlin, A., Damjanović, S., Dietel, T., Dietrich, L., Drees, A., Dubitzky, W., Esumi, S. I., Filimonov, K., Fomenko, K., Fraenkel, Z., Garabatos, C., Glässel, P., Hering, G., Holeczek, J., Kalisky, M., Krobath, G., Kushpil, V., Maas, A., Marín, A., Milošević, J., Miśkowiec, D., Panebrattsev, Y., Petchenova, O., Petráček, V., Radomski, S., Rak, J., Ravinovich, I., Rehak, P., Sako, H., Schmitz, W., Schuchmann, S., Sedykh, S., Shimansky, S., Stachel, J., Šumbera, M., Tilsner, H., Tserruya, I., Tsiledakis, G., Wessels, J. P., Wienold, T., Wurm, J. P., Yurevich, S., & Yurevich, V. Elliptic flow of charged pions, protons and strange particles emitted in Pb+Au collisions at top SPS energy. United States. doi:10.1016/j.nuclphysa.2012.08.004.
Adamová, D., Agakichiev, G., Andronic, A., Antończyk, D., Appelshäuser, H., Belaga, V., Bielčíková, J., Braun-Munzinger, P., Busch, O., Cherlin, A., Damjanović, S., Dietel, T., Dietrich, L., Drees, A., Dubitzky, W., Esumi, S. I., Filimonov, K., Fomenko, K., Fraenkel, Z., Garabatos, C., Glässel, P., Hering, G., Holeczek, J., Kalisky, M., Krobath, G., Kushpil, V., Maas, A., Marín, A., Milošević, J., Miśkowiec, D., Panebrattsev, Y., Petchenova, O., Petráček, V., Radomski, S., Rak, J., Ravinovich, I., Rehak, P., Sako, H., Schmitz, W., Schuchmann, S., Sedykh, S., Shimansky, S., Stachel, J., Šumbera, M., Tilsner, H., Tserruya, I., Tsiledakis, G., Wessels, J. P., Wienold, T., Wurm, J. P., Yurevich, S., and Yurevich, V. Thu . "Elliptic flow of charged pions, protons and strange particles emitted in Pb+Au collisions at top SPS energy". United States. doi:10.1016/j.nuclphysa.2012.08.004.
@article{osti_1079299,
title = {Elliptic flow of charged pions, protons and strange particles emitted in Pb+Au collisions at top SPS energy},
author = {Adamová, D. and Agakichiev, G. and Andronic, A. and Antończyk, D. and Appelshäuser, H. and Belaga, V. and Bielčíková, J. and Braun-Munzinger, P. and Busch, O. and Cherlin, A. and Damjanović, S. and Dietel, T. and Dietrich, L. and Drees, A. and Dubitzky, W. and Esumi, S. I. and Filimonov, K. and Fomenko, K. and Fraenkel, Z. and Garabatos, C. and Glässel, P. and Hering, G. and Holeczek, J. and Kalisky, M. and Krobath, G. and Kushpil, V. and Maas, A. and Marín, A. and Milošević, J. and Miśkowiec, D. and Panebrattsev, Y. and Petchenova, O. and Petráček, V. and Radomski, S. and Rak, J. and Ravinovich, I. and Rehak, P. and Sako, H. and Schmitz, W. and Schuchmann, S. and Sedykh, S. and Shimansky, S. and Stachel, J. and Šumbera, M. and Tilsner, H. and Tserruya, I. and Tsiledakis, G. and Wessels, J. P. and Wienold, T. and Wurm, J. P. and Yurevich, S. and Yurevich, V.},
abstractNote = {Differential elliptic flow spectra v2(pT) of π-, K$0\atop{2}$, p, Λ have been measured at √sNN around midrapidity by the CERN-CERES/NA45 experiment in mid-central Pb + Au collisions (10% of σgeo). The pT range extends from about 0.1 GeV/c (0.55 GeV/c for Λ) to more than 2 GeV/c. Protons below 0.4 GeV/c are directly identified by dE/dx. At higher pT, proton elliptic flow is derived as a constituent, besides π+ and K+, of the elliptic flow of positive pion candidates. This retrieval requires additional inputs: (i) of the particle composition, and (ii) of v2(pT) of positive pions. For (i), particle ratios obtained by NA49 are adapted to CERES conditions; for (ii), the measured v2(pT) of negative pions is substituted, assuming π+ and π- elliptic flow magnitudes to be sufficiently close. The v2(pT) spectra are compared to ideal-hydrodynamics calculations. In synopsis of the series π-, K$0\atop{2}$-p-Λ, flow magnitudes are seen to fall with decreasing pT progressively even below hydro calculations with early kinetic freeze-out (Tf=160 MeV) leaving not much time for hadronic evolution. The proton v2(pT) data show a downward swing towards low pT with excursions into negative v2 values. The pion-flow isospin asymmetry observed recently by STAR at RHIC, invalidating in principle our working assumption, is found in its impact on proton flow bracketed from above by the direct proton flow data, and not to alter any of our conclusions. Results are discussed in perspective of recent viscous hydrodynamics studies which focus on late hadronic stages.},
doi = {10.1016/j.nuclphysa.2012.08.004},
journal = {Nuclear Physics. A},
issn = {0375-9474},
number = C,
volume = 894,
place = {United States},
year = {2012},
month = {11}
}