We report on the first measurement of the triangular v3, quadrangular v4, and pentagonal v5 charged particle flow in Pb-Pb collisions at sqrt(s(NN)) = 2.76 TeV measured with the ALICE detector at ...the CERN Large Hadron Collider. We show that the triangular flow can be described in terms of the initial spatial anisotropy and its fluctuations, which provides strong constraints on its origin. In the most central events, where the elliptic flow v2 and v3 have similar magnitude, a double peaked structure in the two-particle azimuthal correlations is observed, which is often interpreted as a Mach cone response to fast partons. We show that this structure can be naturally explained from the measured anisotropic flow Fourier coefficients.
The centrality dependence of the charged-particle multiplicity density at midrapidity in Pb-Pb collisions at sqrts_{NN}=2.76 TeV is presented. The charged-particle density normalized per ...participating nucleon pair increases by about a factor of 2 from peripheral (70%-80%) to central (0%-5%) collisions. The centrality dependence is found to be similar to that observed at lower collision energies. The data are compared with models based on different mechanisms for particle production in nuclear collisions.
We report the first measurement of charged particle elliptic flow in Pb-Pb collisions at sqrtS(NN) =2.76 TeV with the ALICE detector at the CERN Large Hadron Collider. The measurement is performed in ...the central pseudorapidity region (|η|<0.8) and transverse momentum range 0.2<p t<5.0 GeV/c. The elliptic flow signal v₂, measured using the 4-particle correlation method, averaged over transverse momentum and pseudorapidity is 0.087 ± 0.002(stat) ± 0.003(syst) in the 40%-50% centrality class. The differential elliptic flow v₂ p t reaches a maximum of 0.2 near p t =3 GeV/c. Compared to RHIC Au-Au collisions at sqrtS(NN) 200 GeV, the elliptic flow increases by about 30%. Some hydrodynamic model predictions which include viscous corrections are in agreement with the observed increase.
The ratio of the yields of antiprotons to protons in pp collisions has been measured by the ALICE experiment at sqrts=0.9 and 7 TeV during the initial running periods of the Large Hadron Collider. ...The measurement covers the transverse momentum interval 0.45<p_{t}<1.05 GeV/c and rapidity |y|<0.5. The ratio is measured to be R_{|y|<0.5}=0.957±0.006(stat)±0.014(syst) at 0.9 TeV and R_{|y|<0.5}=0.991±0.005(stat)±0.014(syst) at 7 TeV and it is independent of both rapidity and transverse momentum. The results are consistent with the conventional model of baryon-number transport and set stringent limits on any additional contributions to baryon-number transfer over very large rapidity intervals in pp collisions.
Physical motivations of vector meson (
ϕ and
ω) production study in heavy-ion collisions are discussed using the theoretical predictions and the recent experimental results at SPS and RHIC. A ...simulation study of
ϕ and
ω (and J/
ψ for comparison) production through hadronic and leptonic decays in the ALICE detector at LHC is presented for Pb–Pb ans p–p collisions. The possibility to select the resonance signals over the combinatorial backgrounds is demonstrated using a realistic simulation of tracking and particle identification in the ALICE offline framework.
Photon flow in 158 A GeV Pb+Pb collisions Nikolaev, Sergey; Aggarwal, M.M.; Angelis, A.L.S. ...
Nuclear Physics A,
2003, Volume:
715
Journal Article, Conference Proceeding
Peer reviewed
Directed and elliptic flow of π
0 - decay photons in 158 A GeV Pb+Pb collisions has been studied near midrapidity in an analysis of data obtained with the photon spectrometer LEDA of the WA98 ...experiment at the CERN SPS. Preliminary results on the rapidity and transverse momentum dependence of the flow have been obtained for various centralityclasses for
p
T
> 0.2GeV/c and 2.3 <
y < 2.9. The results are compared with the pion flow.
Disoriented Chiral Condensates (DCC) have been predicted to form in high energy heavy ion collisions where the approximate chiral symmetry of QCD has been restored. This leads to large imbalances in ...the production of charged to neutral pions. Sophisticated analysis methods are being developed to disentangle DCC events out of the large background of events with conventionally produced particles. We present a short review of current analysis methods and future prospects.
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