Andrea Agostinelli

Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at root S-NN=2.76 TeV

Article history: Received 28 May 2012 Received in revised form 28 November 2012 Accepted 28 December 2012 Available online 4 January 2013 Editor: V. Metag The elliptic, v2, triangular, v3, and quadrangular, v4, azimuthal anisotropic flow coefficients are measured for unidentified charged particles, pions, and (anti-)protons in Pb–Pb collisions at √ sNN = 2.76 TeV with the ALICE detector at the Large Hadron Collider. Results obtained with the event plane and four-particle cumulant methods are reported for the pseudo-rapidity range |η| < 0.8 at different collision centralities and as a function of transverse momentum, pT, out to pT = 20 GeV/c. The observed non-zero elliptic and triangular flow depends only weakly on transverse momentum for pT > 8 GeV/c. The small pT dependence of the difference between elliptic flow results obtained from the event plane and fourparticle cumulant methods suggests a common origin of flow fluctuations up to pT = 8 GeV/c. The magnitude of the (anti-)proton elliptic and triangular flow is larger than that of pions out to at least pT = 8 GeV/c indicating that the particle type dependence persists out to high pT.

Particle-Yield Modification in Jetlike Azimuthal Dihadron Correlations in Pb-Pb Collisions at root S-NN=2.76 TeV

The yield of charged particles associated with high-p(t) trigger particles (8<p(t)<15 GeV/c) is measured with the ALICE detector in Pb-Pb collisions at √s(NN)=2.76 TeV relative to proton-proton collisions at the same energy. The conditional per-trigger yields are extracted from the narrow jetlike correlation peaks in azimuthal dihadron correlations. In the 5% most central collisions, we observe that the yield of associated charged particles with transverse momenta p(t)>3 GeV/c on the away side drops to about 60% of that observed in pp collisions, while on the near side a moderate enhancement of 20%-30% is found.

Measurement of electrons from beauty hadron decays in pp collisions at root s=7 TeV

The production cross section of electrons from semileptonic decays of beauty hadrons was measured at mid-rapidity (|y| < 0.8) in the transverse momentum range 1 < pt < 8 Gev/c with the ALICE experiment at the CERN LHC in pp collisions at a center of mass energy sqrt{s} = 7 TeV using an integrated luminosity of 2.2 nb^{-1}. Electrons from beauty hadron decays were selected based on the displacement of the decay vertex from the collision vertex. A perturbative QCD calculation agrees with the measurement within uncertainties. The data were extrapolated to the full phase space to determine the total cross section for the production of beauty quark-antiquark pairs.

Two- and three-pion quantum statistics correlations in Pb-Pb collisions at root S-NN=2.76 TeV at the CERN Large Hadron Collider

Correlations induced by quantum statistics are sensitive t o the spatio-temporal extent as well as dynamics of particle emitting sources in heavy-ion collision . In addition, such correlations can be used to search for the presence of a coherent component of pion pro ducti n. Twoand three-pion correlations of same and mixed-charge are measured at low relativ momentum to estimate the coherent fraction of charged pions in Pb-Pb collisions at √ sNN = 2.76 TeV at the CERN Large Hadron Collider with ALICE. The genuine three-pion quantum statistics corr elation is found to be suppressed relative to the two-pion correlation based on the assumption of fully chaotic pion emission. The suppression is observed to decrease with triplet momentum. The observed suppression at low triplet momentum may correspond to a coherent fraction in charged pion emissi on of 23%±8%. ∗See Appendix B for the list of collaboration members Two and Three-Pion Quantum Statistics Correlations ALICE C ollaboration