Abstract

The directed flow of charged particles at midrapidity is measured in Pb-Pb collisions at root s(NN) p 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 p(T) between 1.2 and 1: 7 GeV/c. Combined with the observation of a vanishing rapidity-even p(T) 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

• Di Bari Domenico , Fiore Enrichetta Maria , Volpe Giacomo

Tutti gli autori

• MASTROSERIO A.;DI BARI D.;FIORE E.M.;VOLPE G.

Titolo volume/Rivista

Non Disponibile

Anno di pubblicazione

2013

ISSN

0031-9007

ISBN

Non Disponibile

Numero di citazioni Wos

34

Ultimo Aggiornamento Citazioni

Non Disponibile

Numero di citazioni Scopus

Non Disponibile

Ultimo Aggiornamento Citazioni

Non Disponibile

Settori ERC

Non Disponibile

Codici ASJC

Non Disponibile