Abstract

The directed flow of charged particles at midrapidity is measured in Pb-Pb collisions at ffiffiffiffiffiffiffiffi sNN p ¼ 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.

Autore Pugliese

• Bruno Giuseppe Eugenio

Tutti gli autori

• Bruno G.E. , et al.

Titolo volume/Rivista

PHYSICAL REVIEW LETTERS

Anno di pubblicazione

2013

ISSN

0031-9007

ISBN

Non Disponibile

Numero di citazioni Wos

Nessuna citazione

Ultimo Aggiornamento Citazioni

Non Disponibile

Numero di citazioni Scopus

18

Ultimo Aggiornamento Citazioni

2017-04-22 03:20:59

Settori ERC

Non Disponibile

Codici ASJC

Non Disponibile