1 ALICE A Large Ion Collider Experiment 2 ALICE An experiment dedicated to the study of nucleus-nucleus collisions at LHC An experiment dedicated to the study of nucleus-nucleus collisions at LHC Why nucleus-nucleus collisions?Why nucleus-nucleus collisions? Heat and compress matter......to a temperature about 100,000 times the temperature in the centre of the Sun and...to a temperature about 100,000 times the temperature in the centre of the Sun and...to densities such that all matter contained in the Kheops pyramid would fit in a pinhead...to densities such that all matter contained in the Kheops pyramid would fit in a pinhead Why would you do that?Why would you do that? To recreate conditions of density and pressure bringing us back to only a few s after the Big Bang To recreate conditions of density and pressure bringing us back to only a few s after the Big Bang In a system we can study in the Lab! In a system we can study in the Lab! 3 Quantum Chromodynamics : the theory of the strong interaction Quarks carry a charge called color; there are 3 colors R, B, GQuarks carry a charge called color; there are 3 colors R, B, G Quarks interact by exchanging a gluon (m g =0) which also carries a color charge!Quarks interact by exchanging a gluon (m g =0) which also carries a color charge! This interaction is strong at large distance and weak at small distance !This interaction is strong at large distance and weak at small distance ! 4 Quarks (valence) are bound inside hadrons (baryons and mesons) so as to form colorless objectsQuarks (valence) are bound inside hadrons (baryons and mesons) so as to form colorless objects Interactions of valence quarks with the vacuum contribute to the mass of hadronsInteractions of valence quarks with the vacuum contribute to the mass of hadrons It is not possible to isolate a color chargeIt is not possible to isolate a color charge q q F=kR 1 q q F=kR 2 q q F=kr 2 q q F=kr 1 5 Big Bang Until seconds after the birth of the Universe, matter is colored: quarks and gluons move freely. As soon as the universe has cooled down to about K, matter becomes colourless: quarks and gluons are locked into hadrons 6 QCD Thermodynamics We are here The Big Bang started here And we will study this trajectory Pb collisions at LHC will take us there 7 Laboratory 2. The energy of collision is materialized into quarks and gluons 1. Accelerated ions will collide head on The mini Big Bang 3. Quarks and gluons interact via the strong interaction: matter equilibrates v/c = 0, Lorentz Contraction : 7 fm 0,003 fm t~ s T~5x10 12 K 4. The system expands and cools down 5. Quarks and gluons condense into hadrons t~ s T~10 12 K 8 SPS: New State of Matter created at CERN (10 Feb. 2000) 7 dedicated experiments (NAxx, WAyy) 7 dedicated experiments (NAxx, WAyy) Compelling evidence for the existence of a new state of matter ( 3.2 GeV/fm 3 ] > c, strangeness enhancement, J/ suppression, direct thermal photon radiation,) Compelling evidence for the existence of a new state of matter ( 3.2 GeV/fm 3 ] > c, strangeness enhancement, J/ suppression, direct thermal photon radiation,) Interpretation in terms of QGP formation not unique Interpretation in terms of QGP formation not unique Pb+Pb s NN = 17.3 GeV NA 49 9 RHIC: The QGP at RHIC (M. Gyulassy QM 2004) 4 multipurpose experiments (BRAHMS, PHENIX, PHOBOS, STAR) 4 multipurpose experiments (BRAHMS, PHENIX, PHOBOS, STAR) Empirical lines of evidence: Empirical lines of evidence: Energy density (5 GeV/fm 3 ) well beyond critical value Large elliptic flow: early collective behavior at partonic level Jet quenching, mono jets: absorption of partons in a color dense opaque medium dA control experiment Interpreted in terms of a strongly coupled QGP and a new QCD state (?) C olor G lass C ondensate Interpreted in terms of a strongly coupled QGP and a new QCD state (?) C olor G lass C ondensate Au+Au s NN = 200 GeV STAR 10 11 Accelerates 710 12 eV & 2,7610 12 eV ( % c) Accelerates 710 12 eV & 2,7610 12 eV ( % c) ~10 8 ions cross 10 8 ions 10 6 times every second ~10 8 ions cross 10 8 ions 10 6 times every second 8,000 collisions every second, out of which 1% produce extraordinary events 8,000 collisions every second, out of which 1% produce extraordinary events LHC: The closest approximation of the Big Bang One heavy ion experiment, ALICE, + CMS & ATLAS; One heavy ion experiment, ALICE, + CMS & ATLAS; In 04/2007, LHC will deliver first pp at 14 TeV collisions, In 04/2007, LHC will deliver first pp at 14 TeV collisions, and soon after PbPb collisions at s NN = 5.5 TeV. and soon after PbPb collisions at s NN = 5.5 TeV. 12 ALICE : The answer to the challenge 13 ALICE: the dedicated HI experiment Solenoid magnet 0.5 T Central tracking system: ITS TPC TRD TOF MUON Spectrometer: absorbers tracking stations trigger chambers dipole Specialized detectors: HMPID PHOS 14 Internal tracking (ITS): p, id 15 TPC ALICE Readout plane segmentation 18 trapezoidal sectors each covering 20 degrees in azimuth E E 510 cm E E 88 s GAS VOLUME 88 m 3 DRIFT GAS 90% Ne - 10%CO 2 PbP E E 5 m 5.6 m V / cm NE / CO 2 88 s End plate Central electrode Drift volume 16 What we should be prepared for 60 < < 62 One collision : 5.5 TeV dN/dy = 8,000 17 The to-do programme About 16,000 particles cross the detectors in each collision ; the particle density reaches 90 particles per cm 2, near the interaction point ! About 16,000 particles cross the detectors in each collision ; the particle density reaches 90 particles per cm 2, near the interaction point ! Measure every particle individually: count them, localise their trajectory, identify their nature, establish their 4-momentum ; Measure every particle individually: count them, localise their trajectory, identify their nature, establish their 4-momentum ; Localise the origin within a few m ; Localise the origin within a few m ; Identify the interesting rare events in less than 100 s ; Identify the interesting rare events in less than 100 s ; Store data 1.2 Gb/s (2 CD/s) et 1 Pb/y (a 4 Km high CD pile) ; Store data 1.2 Gb/s (2 CD/s) et 1 Pb/y (a 4 Km high CD pile) ; Give access to data to 1,000 physicists spread in 80 institutes in 28 countries. Give access to data to 1,000 physicists spread in 80 institutes in 28 countries. 18 AA Physics Menu at LHC Global properties Global properties Multiplicities, distributions, zero degree energyMultiplicities, distributions, zero degree energy Event history Event history Boson interferometryBoson interferometry Resonance decaysResonance decays Fluctuations and critical behaviour Fluctuations and critical behaviour Event-by-event particle composition and spectroscopyEvent-by-event particle composition and spectroscopy Neutral to charged ratioNeutral to charged ratio Degrees of Freedom vs Temperature Degrees of Freedom vs Temperature Hadron ratios and spectraHadron ratios and spectra Dilepton continuumDilepton continuum Direct photonsDirect photons Collective effects Collective effects Elliptic flowElliptic flow Deconfinement, chiral simmetry restoration Deconfinement, chiral simmetry restoration Charmonium, bottonium spectroscopyCharmonium, bottonium spectroscopy (Multi-)strange particles(Multi-)strange particles Partonic energy loss in QGP Partonic energy loss in QGP Jet quenching, high p T spectraJet quenching, high p T spectra Open charm and beautyOpen charm and beauty W , Z 0,... W , Z 0,... 19 From volts to bytes The signal of each cell (~16 millions) is procesed by highly integrated electronic systems ; The signal of each cell (~16 millions) is procesed by highly integrated electronic systems ; The electric signal is digitised to be processed by computers ; The electric signal is digitised to be processed by computers ; The information is transported by optical fibers. The information is transported by optical fibers. 20 To process the data Yerevan CERN Saclay Lyon Dubna Capetown, ZA Birmingham Cagliari NIKHEF GSI Catania Bologna Torino Padova IRB Kolkata, India OSU/OSC LBL/NERSC Merida Bari Nantes Distributing ressources : CPU Data storage Are distributed around the world 21 Time projection chamber (TPC) : p, id