Naslov
Directed flow of charged particles at midrapidity relative to the spectator plane in Pb-Pb collisions at sNN−−−−√=2.76  TeV

Autori
Abelev, B. ; ... ; Antičić, Tome ; ... ; Gotovac, Sven ; ... ; Mudnić, Eugen ; ... ; Planinić, Mirko ; ... ; Poljak, Nikola ; ... ; Simatović, Goran ; ... ; Šuša, Tatjana ; ... ; Vicković, Linda ; ... ; Zyzak, M.

Izvornik
Physical Review Letters (0031-9007) 111 (2013), 23; 232302-1

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
heavy ion; Pb-Pb; flow; plasma

Sažetak
The directed flow of charged particles at midrapidity is measured in Pb-Pb collisions at sNN−−−√=2.76  TeV relative to the collision symmetry plane defined by the spectator nucleons. A negative slope of the rapidity-odd directed flow component with approximately 3 times smaller magnitude than found at the highest RHIC energy is observed. This suggests a smaller longitudinal tilt of the initial system and disfavors the strong fireball rotation predicted for the LHC energies. The rapidity-even directed flow component is measured for the first time with spectators and found to be independent of pseudorapidity with a sign change at transverse momenta pT between 1.2 and 1.7  GeV/c. Combined with the observation of a vanishing rapidity-even pT shift along the spectator deflection this is strong evidence for dipolelike initial density fluctuations in the overlap zone of the nuclei. Similar trends in the rapidity-even directed flow and the estimate from two-particle correlations at midrapidity, which is larger by about a factor of 40, indicate a weak correlation between fluctuating participant and spectator symmetry planes. These observations open new possibilities for investigation of the initial conditions in heavy-ion collisions with spectator nucleons.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

Napomena
ALICE Collaboration.

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