1. The Quest for the Quark-Gluon-Plasma: The High-Energy Frontier Why Heavy Ions at the LHC? Where we stand What lies ahead Paolo Giubellino INFN Torino Paris Nov 2004

2. The Relativistic Heavy Ion Collider At Brookhaven National Laboratory At the moment the hunting ground for the Quark Gluon Plasma is across the Ocean …

3. The Large Hadron Collider … But the future place for studying the Quark Gluon Plasma is back in Europe!

4. Nuclear accelerators The LHC latest of a series of successful accelerators –After many problems have been overcome, both technical and financial, startup is foreseen for 2007, with first HI run in 2008 / 2007 (transparency from H. Specht, 1992)

5. Heavy-Ion Physics @ LHC ~1100 participants: (~two thirds from NUPECC countries) 1000 ALICE 60 CMS 25 ATLAS A large community which has been constantly growing over the years, and still grows! => VERY lively field!!! 0 200 400 600 800 1000 1200 19901992199419961998200020022004 ALICE Collaboration statistics LoI MoU TP TRD

6. Past/Present/Future of the high-energy frontier AGS/SPS: 1986 – 1994 – existence & properties of hadronic phase, proof of principle of the method chemical & thermal freeze-out, collective flow,… SPS: 1994 – 2003 (new results just coming: NA60) – Building a coherent picture. 'compelling evidence' for new state of matter with many properties predicted for QGP J/Y suppression (deconfinement ?) low mass lepton pairs (chiral restoration ?) RHIC: 2000 - ? – compelling evidence -> establishing the QGP ? parton flow, parton energy loss Huge flux of results, tens of papers! – however: soft ~ semihard; lifetime hadron ~ parton phase LHC: 2007 - ?? (typ. > 10 yrs, see CDF) – (semi)hard >> soft, lifetime parton >> hadron phase – precision spectroscopy of ideal plasma QGP heavy quarks (c,b) Both Quarkonia and Open Charm & Beauty, Jets, Y, thermal photons LHC: will open the next chapter in HI physics significant step over & above existing facilities THE THE place to do frontline research after 2007

7. Jet properties

8. Why at the LHC? - I Qualitatively new regime! m u = m d = m s m u = m d m u = m d ; m s m u,d HQ suppressed exp(-m c,b,t /T) T c ~ m s T well above T c

9. Why at the LHC?-II Tools @LHC Hard processes contribute significantly to the total AA cross- section: –Bulk properties dominated by hard processes; –Very hard probes are abundantly produced. Weakly interacting probes become accessible. Hard probes have provided the most remarkable RHIC results: R AA dep. on P T, away-jet disappearance etc … ALICE, with its tracking and PID is perfect for the task

10. Why at the LHC?-III Heavy Quarks Copiously produced Y d /dy LHC ~ 20 x RHIC ALICE also measures B & D production => proper normalization! Events/100 MeV 10 3 J/ Y 51015 10 2 dN/d=8000 M + - (GeV) 0 2.5 < < 4 c/b Quarkonia in ALICE 1 month statistics of PbPb sNN=5.5 TeV Y production RHICLHC R. Vogt, hep-ph/0205330

11. SPSRHICLHC s NN (GeV)17200 dN ch /dy500850 0 QGP (fm/c) 10.2 T/T c 1.11.9 (GeV/fm 3 ) 35 QGP (fm/c) 22-4 f (fm/c) ~1020-30 V f (fm 3 )few 10 3 few 10 4 few 10 5 5500X 28 1500-8000? 0.1faster 3.0-4.2hotter 15-60denser 10 longer 30-40 Quantitatively new regime! Why at the LHC? - IV

12. Summary: ALICE Physics goals (have evolved along the years, to cover practically all relevant observables) (in one experiment what at the SPS was done by 6-7 experiments, at RHIC by 4) Deconfinement: charmonium and bottonium spectroscopy Chiral symmetry restoration: neutral to charged ratios, res. decays Fluctuation phenomena - critical behavior: event-by-event particle comp. and spectra Geometry of the emitting source: HBT, impact parameter via zero-degree energy flow pp collisions in a new energy domain Large acceptance Good tracking capabilities Selective triggering Excellent granularity Wide momentum coverage P.I.D. of hadrons and leptons Good sec. vertex reconstr. Photon Detection Use a variety of experimental techniques! Global observables: Multiplicities, distributions Degrees of freedom as a function of T hadron ratios and spectra, dilepton continuum, direct photons Early state manifestation of collective effects: elliptic flow Energy loss of partons in quark gluon plasma: jet quenching, high pt spectra, open charm and open beauty

13. ALICE central event N ch (-0.5< <0.5)=8000 The ALICE Challenge!

14. Getting ready… ALICE represents an extraordinary expermental challenge => its preparation motivated many vigorous R&D programs In detector Hardware and VLSI Electronics => successfully completed across the decade of the 1990's: –Inner Tracking System (ITS) Silicon Pixels (RD19) Silicon Drift (INFN/SDI) Silicon Strips (double sided) low mass, high density interconnects low mass support/cooling –TRD radiators bi-dimensional (time-space) read-out, on-chip trigger (TRAP chip) –TPC gas mixtures (RD32) advanced digital electronics low mass field cage – EM calorimeter new scint. crystals (RD18) – PID Multigap RPC's (LAA) solid photocathode RICH (RD26) In DAQ & Computing => in progress now – scalable architectures with consumer electornics commercial components (COTS) – high perf. storage media – GRID computing

15. Example: ITS Electronics Developments (all full-custom designs in rad. tol., 0.25 m process) Preamplifiers Analogue memory ADC s ALICE PIXEL CHIP 50 µm x 425 µm pixels 8192 cells Area: 12.8 x 13.6 mm 2 13 million transistors ~100 µW/channel ALICE SDD FEE Pascal chip: 64 channel preamp+ 256-deep analogue memory+ ADC Ambra chip: 64 channel derandomizer chip ALICE SSD FEE HAL25 chip: 128 channels Preamp+s/h+ serial out And extreme lightweight interconnection techniques: SSD tab-bondable Al hybrids

16. DOUBLE STACK OF 0.5 mm GLASS Edge of active area cathode pick up pad anode pick up pad Resistive layer (cathode) Resistive layer (anode) 5 gaps - 0.9 < < 0.9 full for, K, p PID, K for p <2 GeV/c p for p <4 GeV/c full size TOF modules under test Multigap Resistive Plate Chambers Example:Time Of Flight Breakthrough after > 5 years of R&D 05001000-500 -1000 1200 1000 800 600 400 200 0 STRIP 10 H.V. +- 6 kV Time with respect to timing scintillators [ps] = 53 ps minus 30 ps jitter of timing scintillator = 44 ps Entries/50 ps Typical time spectrum 150 kchann. over ~150 m 2

17. ALICE LAYOUT: TRACKING (and event characterization) Inner Tracking System (ITS): 6 Si Layers (pixels, drift, strips) Vertex reconstruction, dE/dx -0.9< <0.9 ZDC (impact parameter) Forward Multiplicity Detectors T0 detectors (event time) V0 detectors (trigger) TPC Tracking, dE/dx -0.9< <0.9 TRD Tracking and High-P t Trigger -0.9< <0.9

18. ALICE LAYOUT: PID TOF PID (K,p, ) -0.9< <0.9 HMPID: High Momentum Particle Identification (, K, p) RICH Hard Probes TRD Identification of electrons (p>1 GeV/c) -0.9< <0.9 MUON arm Dimuons and vector mesons 2.4 < < 4

19. ALICE LAYOUT: photons PHOS: high-granularity, high- resolution detector PbWO 4 crystals photons and neutral mesons -jet tagging PMD: Photon Multiplicity Detector Preshower detector with fine granularity Coverage: 2.3< <3.5, 270 k channels E-by-E fluctuaction, DCC, flow

20. ALICE tracking can fully exploit the high p t signals which will become accessible at the LHC, even at the highest multiplicities 10 100 p t (GeV/c) 50 p/p (%) 10 30 50 100 GeV/c ALICE PPR CERN/LHCC 2003-049 ALICE momentum resolution at high pt

21. ALICE PID performance

22. STAR open charm in dAu D 0 K - + reconstruction in ALICE Search for thermal charm production Signals which are just hints at RICH becomes tools at the LHC: need Luminosity and the higher cross-section given by the higher Energy! Example of the power of ALICE tracking + PID + vertexing

23. Getting ready … The infrastructure is taking shape All detectors are now in full construction phase –About 2/3 of ALICE construction budget has been spent –Major construction, test, integration and commissioning effort, putting the facilities and the technical and scientific staff of all the ~80 ALICE laboratories under enormous stress A prolonged effort is ongoing, requiring an amazing cohesion and commitment from the collaborators … and a lot of support from their institutions: 2003, 2004, 2005, and part of 2006: construction 2006 and part of 2007: final integration and commissioning, while deploying the tools for DAQ and data analysis

24. The ALICE Magnet: ready for the experiment to move in! still largest magnet – magnet volume: 12 m long, 12 m high – 0.5 T solenoidal field

25. The Space Frame …

26. Muon Magnet 0.7 T and 3Tm 4 MW power, 800 tons Worlds largest warm dipole

27. TPC Field Cage

28. TPC R/O chambers production finished in Bratislava and GSI

29. Muon Chambers Station 3-4: Slats Trigger RPC Station 1&2: Quadrants

30. ITS modules Now being produced in series…. Hybrid bonding on K&S manual bonder Pixel Strip Drift

31. And a lot more… (just very few examples!) TRD stack under test Muon trigger chamber PHOS PbWO 4 Crystals ZDC V0 Prototyp e

32. ALICE DC III Computing Phase Transition – Online: storing up to 1.2 Gbyte/s whole WWW in few hours on tape ! ~ 10 x RHIC ! – Offline: ~22 MegaSI2000 22000 PC's in 2004 (2800 Mhz) ~6 PB on disk per year – cheap mass market components Industry & Moore's law – make 100,000 mice do the work of one elephant: new computing paradigm: The GRID The Problem: The Answer:The Challenge:

33. ALICE features the Largest Grid in operation: for ALICE Distributed computing with GRID tools is already a reality! 40 centres in three continents, 7000 CPUs, 100TB of storage In operation in the last 9 months 1 million jobs 500 MSI2k hours CPU (one PC for 60 years!) 200 TB transferred from CERN Next challenge: distributed data analysis, using ALICE E2E analysis prototype end to UIapplication middleware shell

34. Getting ready… But a lot remains to be done! Some crucial items will come after 2007 and/or have still non- confirmed funding : –DAQ (100% bandwidth foreseen for 2008) –High Level Trigger –Remaining 40% of TRD (recommended already at time of approval in Jan 2002 by the LHCC) –The 5 PHOS modules will come The first three one per year in 2006/7/8 The last two only if more funds are available The GRID progresses, yet the huge resources in hardware, software and system management needed for the offline must still be secured. Even later: Large-Acceptance EMcal for jets (proposed by a collaboration of 13 US institutions) ALICE at startup will not be fully equipped for hard Physics => OK since soft Physics will be addressed first (Luminosity will grow with time). However, the full potential of ALICE can only be realized when the combined complementary information of all its detector systems will be available.