Francesco Noferini Centro Studi e Ricerche E. Fermi (Roma) INFN Sez. Bologna Roma, Particle correlations in heavy ion collisions for the ALICE experiment at the LHC Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Summary Predictions for the QGP ; Results from RHIC ; The ALICE experiment; A new analysis method for particle correlations - Fourier Analysis -; Results from Monte Carlo simulations. Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Predictions for the QGP Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Predictions from lattice calculations Deconfinement is expected for high density over a critical temperature of 175 MeV. The strong coupling between two quarks is expected to vanish for T > T C. Heavy ion collisions are the suitable environment to probe it. Lattice calculations taken by: O.Kaczmarek and F.Zantow, Phys. Rev. D 71 (2005) Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Predictions from lattice calculations (II) Phase transition occurs at very high density and temperature. Chemical potential vanishes when the centre-of-mass energy of the colliding system increases. In this case the order of the transition changes from the FIRST to a CROSS OVER. RHIC & LHC Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Observables for the QGP Chemical probes Kinetic probes Strangeness enhancement and vector-meson production Effects on J/ and B-production High p T probes Electromagnetic probes Statistical models. m s T. Jet-medium interaction. Early stages of the interaction. Collective phenomena (flow) represent also a signature of the existence of a partonic medium and provide a way to probe the medium properties! Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Results from RHIC Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Strong QGP: elliptic flow Expansion is driven by a gradient of pressure There is a preferential direction for particle emission dN/d 2v22v2 Peripheral collision Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, RHIC results: elliptic flow Results for 2 at moderate p T are consistent with an ideal strong interacting fluid at 0 viscosity. The p T dependence of anisotropy scaled by the hadron quark content shows a universal behaviour (coalescence). RR J. Adams et al. [STAR Collaboration], Phys. Rev. C 72 (2005) Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, RHIC results: jet quenching High p T hadron suppression as a signature of the jet-medium interaction. Medium seems to be transparent to photons. colored medium. T. Isobe [PHENIX Collaboration], AIP Conf. Proc. 842 (2006) 56 Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, RHIC results: two-particle correlations The first RHIC result for jet quenching was the away side suppression of the jet correlation in AA collisions. For this reason the back-to-back correlation suppression showed a centrality dependence. D + Au AuAu central J. Adams et al. [STAR Collaboration], Phys. Rev. Lett. 91 (2003) J. Adams et al. [STAR Collaboration], Phys. Rev. Lett. 97 (2006) No centrality dependence Suppressed when centrality increases Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, The ALICE experiment Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, The charged multiplicity expected for PbPb collisions at LHC is per unit rapidity. p T > 2 GeV/c p T > 1 GeV/c p T > 0.5 GeV/c 4 m PbPb HIJING events - b < 5 fm The ALICE environment Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, The ALICE detector Solenoid magnet 0.5 T PHOS ITS PMD HMPID TOF TRD Muon Arm TPC FMD T0,V0,ZDC Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, A new analysis method for particle correlations - Fourier Analysis - Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, N The method idea N corr peak FFT Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Fourier analysis (I) Calculate the spectrum for each event. Average over all the events in order to select the most significant, loosing the phase information. Draw the function with the average spectrum. (FFT = Fast Fourier Transform) Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Advantages of this kind of analysis w.r.t. the traditional one In principle it can reconstruct any kind of azimuthal and eta correlation. It doesnt need any trigger contrarily to the two-particle correlation method. It works at intermediate p T, where the number of (mini)jets per event is very large. OTHER PROPERTIES It counts for all the correlations of any particle with each other. It works also in case of a superposition of many signals (jets), and in this case the amplitude of the reconstructed distribution follows a - dependence ( is the number of jets). Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, N jet dependence True distribution Reconstructed distribution True distribution Reconstructed distribution True distribution Reconstructed distribution True distribution Reconstructed distribution Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Charge correlations The convolution of the jet shape with itself: SAME SIGN CORRELATIONS OPPOSITE SIGN CORRELATIONS Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Results from Monte Carlo simulations Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Jet correlations in PYTHIA MC pp hard processes generated with p T > 2 ; Samples of events with a fixed number of jets ( N jet ) were created (overlap of PYTHIA events); The dependence of the reconstructed shape on the number of jets per event was tested. N jet =10 N jet =100 N jet =1 Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Jet correlations in PYTHIA MC PYTHIA (true) N jet = 1 PYTHIA N jet = 10 PYTHIA N jet = 1 PYTHIA N jet = 100 Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Monte Carlo generation (PYTHIA, HIJING, ) Track propagation (GEANT3) Digitization Signal similar to reality Final reconstruction Kinematics.root xxxHits.root xxx = for a single detector xxxSDigits.root xxxDigits.root xxx = for a single detector AliESDs.root Reconstruction with the ALICE detector for pp collisions Simulations of pp events and of the ALICE detector response showed a very good efficiency and precision in the final reconstructed shape with the FFT method. Analyses on 20k fully reconstructed events Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Jet quenching effects in PYTHIA an improved approach Quenching effects are introduced in PYTHIA according to BDMPS- WS weights and Glauber geometry (Parton Quenching Model).BDMPS- WS low p T Enhancement at low p T due to radiated gluons Suppression at high p T only in the back-to-back correlation Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Fully reconstructed HIJING events Comparison between the shape reconstructed with the information from MC ( blue line ) and that after the simulation of the whole detector response ( black line ). The analysis on the fully reconstructed data is not yet corrected for efficiency. Analyses on 200 fully reconstructed events Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Resonances and Charge correlations The contribution due to several resonances in different channel is tested for: 0 + - + - + - K + K - K *0, K *0 K + -,K - + Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Contribution from the resonances to oppostite sign correlations Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Conclusions A new method addressing jet properties, complementary to two-particle correlations, was presented. The method works in a scenario of multiple production of jets in AA events. This feature is important to probe correlations at low p T at the LHC energy because of the big amount of mini-jets produced. The intrinsic capability of the method to reconstruct the original shape of the jet was also presented. This kind of analysis represents a major tool to investigate the production of QGP at LHC through measurements of jet energy loss (& elliptic flow). An improved model for the treatment of jet quenching was developed and tested. First significant results to demonstrate the sensitivity of the method in the ALICE experiment were shown. Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Experimental: Two particle correlations same/opposite sign Opposite sign (+-) Same sign (++,- -) chain-like charge-ordering RHIC data at Nuclear Physics A715 (2003) 272 Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Time Of Flight (TOF) MRPC system 18 sectors covering the whole azimuthal angle, | | 99%. Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, N jet dependence TOY MODEL E jet = 10 GeV A=1 GeV/c, kT =0.3 GeV/c p T cut = 0.5 GeV/c Sec 1Sec 2Sec 3Sec 4Sec 5backupConclusions Roma, Direct measurement of elliptic flow Reconstruction of the flow contribution from the spectrum. b = A 2 / (A 0 / 2) as a function of p T.